[audio] added sdl audio backend and in-tree atrac9 decoder

src/SharpEmu.HLE/Host/GuestAudioClock.cs

@@ -0,0 +1,69 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Diagnostics;
+
+namespace SharpEmu.HLE.Host;
+
+/// <summary>
+/// How much guest audio the host device has actually played, in seconds.
+///
+/// This is the only clock in the emulator that advances at the rate the player
+/// hears. Wall clock runs ahead of it whenever the guest cannot feed the device
+/// (the stream underruns and the missing time is never played), so anything
+/// that has to stay in step with the guest's audio — host-decoded video being
+/// the case that matters — has to follow this rather than <see cref="Stopwatch"/>.
+///
+/// Reported per stream and kept as the furthest-along value: the guest's ports
+/// all carry one mix, and the leading port is the one whose position the
+/// listener perceives.
+/// </summary>
+public static class GuestAudioClock
+{
+    private static long _playedMicroseconds;
+    private static long _lastAdvanceTimestamp;
+
+    /// <summary>Seconds of guest audio the device has played. Monotonic.</summary>
+    public static double PlayedSeconds =>
+        Interlocked.Read(ref _playedMicroseconds) / 1_000_000.0;
+
+    /// <summary>
+    /// True while a stream has reported progress recently. False means no guest
+    /// audio is playing, and callers must fall back to wall clock rather than
+    /// stalling on a clock that will never advance.
+    /// </summary>
+    public static bool IsRunning
+    {
+        get
+        {
+            var last = Interlocked.Read(ref _lastAdvanceTimestamp);
+            return last != 0 &&
+                   Stopwatch.GetElapsedTime(last) < TimeSpan.FromMilliseconds(250);
+        }
+    }
+
+    public static void Report(double playedSeconds)
+    {
+        if (double.IsNaN(playedSeconds) || playedSeconds < 0)
+        {
+            return;
+        }
+
+        var microseconds = (long)(playedSeconds * 1_000_000.0);
+        var current = Interlocked.Read(ref _playedMicroseconds);
+        while (microseconds > current)
+        {
+            var seen = Interlocked.CompareExchange(
+                ref _playedMicroseconds,
+                microseconds,
+                current);
+            if (seen == current)
+            {
+                Interlocked.Exchange(ref _lastAdvanceTimestamp, Stopwatch.GetTimestamp());
+                return;
+            }
+
+            current = seen;
+        }
+    }
+}

src/SharpEmu.HLE/Host/IHostAudioStream.cs

@@ -15,4 +15,17 @@ public interface IHostAudioStream : IDisposable
     /// audio, in which case the caller paces the guest itself.
     /// </summary>
     bool Submit(ReadOnlySpan<byte> stereoPcm16);
+
+    /// <summary>
+    /// Audio already handed to the device and not yet played, in milliseconds —
+    /// the cushion protecting playback from a late submission. Zero means the
+    /// device has run dry and is emitting silence.
+    ///
+    /// Callers that pace the guest against an emulated hardware queue need this:
+    /// pacing purely on wall clock releases exactly one buffer per buffer-period
+    /// and so keeps the cushion at zero, which turns any scheduling jitter into
+    /// an audible dropout. Returns -1 when the backend cannot report a depth, in
+    /// which case callers must fall back to their own pacing.
+    /// </summary>
+    int QueuedMilliseconds => -1;
 }

src/SharpEmu.HLE/Host/IHostPcmAudioOutput.cs

@@ -0,0 +1,19 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.HLE.Host;
+
+/// <summary>
+/// Optional host-audio extension for backends that can accept the guest's
+/// interleaved PCM layout directly and perform device conversion themselves.
+/// </summary>
+public interface IHostPcmAudioOutput : IHostAudioOutput
+{
+    IHostAudioStream OpenPcmStream(uint sampleRate, int channels, HostPcmFormat format);
+}
+
+public enum HostPcmFormat
+{
+    Signed16,
+    Float32,
+}

src/SharpEmu.HLE/Host/Sdl/SdlHostAudio.cs

@@ -0,0 +1,325 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using SDL;
+using static SDL.SDL3;
+
+namespace SharpEmu.HLE.Host.Sdl;
+
+internal sealed unsafe class SdlHostAudio : IHostPcmAudioOutput
+{
+    /// <summary>
+    /// Cap for streams this class paces itself (AudioOut). Blocking the guest
+    /// here is that path's only pacing, so the device settles at this depth —
+    /// it is the playback latency, and the floor under it is how much jitter the
+    /// stream can absorb before it runs dry.
+    /// </summary>
+    private static readonly int TargetQueuedMilliseconds =
+        int.TryParse(
+            Environment.GetEnvironmentVariable("SHARPEMU_AUDIO_LATENCY_MS"),
+            out var latencyMs) && latencyMs > 0
+            ? latencyMs
+            : 60;
+
+    private const int MaximumWaitMilliseconds = 250;
+    private static readonly object InitGate = new();
+    private static bool _initialized;
+
+    public string BackendName => "sdl3";
+
+    /// <summary>
+    /// Stereo PCM16 stream with a caller-chosen backpressure cap. Callers that
+    /// pace the guest themselves pass a deeper cap so this class's backpressure
+    /// does not fight their pacing.
+    /// </summary>
+    public IHostAudioStream OpenStereoPcm16Stream(uint sampleRate, int maxQueuedPcmBytes = 32 * 1024)
+        => OpenStream(
+            sampleRate,
+            channels: 2,
+            HostPcmFormat.Signed16,
+            maxQueuedPcmBytes > 0 ? maxQueuedPcmBytes : 32 * 1024);
+
+    /// <summary>
+    /// Guest-format stream for AudioOut, which has no queue model of its own:
+    /// blocking here is that path's only pacing, so the device settles at
+    /// TargetQueuedMilliseconds and that depth is the playback latency.
+    /// </summary>
+    public IHostAudioStream OpenPcmStream(uint sampleRate, int channels, HostPcmFormat format)
+    {
+        var bytesPerSample = format == HostPcmFormat.Float32 ? sizeof(float) : sizeof(short);
+        var cap = checked((int)((long)sampleRate * channels * bytesPerSample *
+                                TargetQueuedMilliseconds / 1_000));
+        return OpenStream(sampleRate, channels, format, cap);
+    }
+
+    private static IHostAudioStream OpenStream(
+        uint sampleRate,
+        int channels,
+        HostPcmFormat format,
+        int maximumQueuedBytes)
+    {
+        if (sampleRate is < 8_000 or > 384_000 || channels is < 1 or > 8)
+        {
+            throw new ArgumentOutOfRangeException(
+                sampleRate is < 8_000 or > 384_000 ? nameof(sampleRate) : nameof(channels));
+        }
+
+        EnsureInitialized();
+        return new AudioStream(sampleRate, channels, format, maximumQueuedBytes);
+    }
+
+    private static void EnsureInitialized()
+    {
+        lock (InitGate)
+        {
+            if (_initialized)
+            {
+                return;
+            }
+
+            if ((SDL_WasInit(SDL_InitFlags.SDL_INIT_AUDIO) & SDL_InitFlags.SDL_INIT_AUDIO) == 0 &&
+                !SDL_InitSubSystem(SDL_InitFlags.SDL_INIT_AUDIO))
+            {
+                throw new InvalidOperationException($"SDL audio initialization failed: {GetError()}");
+            }
+
+            _initialized = true;
+        }
+    }
+
+    private static string GetError()
+    {
+        var error = Unsafe_SDL_GetError();
+        return error is null ? "unknown SDL error" : Marshal.PtrToStringUTF8((nint)error) ?? "unknown SDL error";
+    }
+
+    private static readonly bool _traceQueue = string.Equals(
+        Environment.GetEnvironmentVariable("SHARPEMU_LOG_AUDIO_QUEUE"),
+        "1",
+        StringComparison.Ordinal);
+
+    private static int _nextStreamId;
+
+    private sealed class AudioStream : IHostAudioStream
+    {
+        private readonly object _gate = new();
+        private readonly int _maximumQueuedBytes;
+        private readonly int _bytesPerFrame;
+        private readonly uint _sampleRate;
+        private readonly int _streamId = Interlocked.Increment(ref _nextStreamId);
+        private SDL_AudioStream* _stream;
+        private bool _disposed;
+        private long _totalSubmittedBytes;
+
+        // Queue diagnostics for the current report window.
+        private long _windowStart = Stopwatch.GetTimestamp();
+        private long _submissions;
+        private long _submittedBytes;
+        private long _blockedTicks;
+        private long _drops;
+        private long _emptyObservations;
+        private int _minQueuedBytes = int.MaxValue;
+        private int _maxQueuedBytes;
+        private long _queuedByteSum;
+
+        public AudioStream(
+            uint sampleRate,
+            int channels,
+            HostPcmFormat format,
+            int maximumQueuedBytes)
+        {
+            var bytesPerSample = format == HostPcmFormat.Float32 ? sizeof(float) : sizeof(short);
+            _bytesPerFrame = channels * bytesPerSample;
+            _sampleRate = sampleRate;
+            var spec = new SDL_AudioSpec
+            {
+                format = format == HostPcmFormat.Float32
+                    ? SDL_AudioFormat.SDL_AUDIO_F32LE
+                    : SDL_AudioFormat.SDL_AUDIO_S16LE,
+                channels = checked((byte)channels),
+                freq = checked((int)sampleRate),
+            };
+
+            _stream = SDL_OpenAudioDeviceStream(
+                SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK,
+                &spec,
+                null,
+                IntPtr.Zero);
+            if (_stream is null)
+            {
+                throw new InvalidOperationException($"SDL audio stream creation failed: {GetError()}");
+            }
+
+            if (!SDL_ResumeAudioStreamDevice(_stream))
+            {
+                SDL_DestroyAudioStream(_stream);
+                _stream = null;
+                throw new InvalidOperationException($"SDL audio stream start failed: {GetError()}");
+            }
+
+            _maximumQueuedBytes = maximumQueuedBytes;
+        }
+
+        public int QueuedMilliseconds
+        {
+            get
+            {
+                lock (_gate)
+                {
+                    if (_disposed || _stream is null)
+                    {
+                        return -1;
+                    }
+
+                    var bytesPerSecond = (double)_bytesPerFrame * _sampleRate;
+                    return bytesPerSecond <= 0
+                        ? -1
+                        : (int)(SDL_GetAudioStreamQueued(_stream) / bytesPerSecond * 1000.0);
+                }
+            }
+        }
+
+        public bool Submit(ReadOnlySpan<byte> pcm)
+        {
+            if (pcm.IsEmpty)
+            {
+                return true;
+            }
+
+            lock (_gate)
+            {
+                if (_disposed || _stream is null)
+                {
+                    return false;
+                }
+
+                var blockStart = Stopwatch.GetTimestamp();
+                var deadline = blockStart +
+                               (Stopwatch.Frequency * MaximumWaitMilliseconds / 1_000);
+                int queued;
+                var overrun = false;
+                while ((queued = SDL_GetAudioStreamQueued(_stream)) > _maximumQueuedBytes)
+                {
+                    if (Stopwatch.GetTimestamp() >= deadline)
+                    {
+                        // Enqueue anyway rather than discarding the buffer. A gap in
+                        // the stream is an audible click; the extra latency of one
+                        // over-deep submission is not, and the queue recovers as soon
+                        // as the device drains back under the cap.
+                        overrun = true;
+                        break;
+                    }
+
+                    Thread.Sleep(1);
+                }
+
+                RecordSubmission(queued, blockStart, dropped: overrun, bytes: pcm.Length);
+                bool submitted;
+                fixed (byte* data = pcm)
+                {
+                    submitted = SDL_PutAudioStreamData(_stream, (nint)data, pcm.Length);
+                }
+
+                if (submitted)
+                {
+                    // Everything handed over minus what the device still holds is
+                    // what the player has actually heard.
+                    _totalSubmittedBytes += pcm.Length;
+                    var bytesPerSecond = (double)_bytesPerFrame * _sampleRate;
+                    if (bytesPerSecond > 0)
+                    {
+                        GuestAudioClock.Report(
+                            Math.Max(0, _totalSubmittedBytes - queued - pcm.Length) / bytesPerSecond);
+                    }
+                }
+
+                return submitted;
+            }
+        }
+
+        /// <summary>
+        /// Samples the queue depth at the moment the guest was allowed to write.
+        /// That depth is the playback latency the guest's audio is subject to, so
+        /// it is the number to look at when the sound is late; an observed depth
+        /// of zero is a genuine underrun, which is what a crackle sounds like.
+        /// Caller holds <see cref="_gate"/>.
+        /// </summary>
+        private void RecordSubmission(int queuedBytes, long blockStart, bool dropped, int bytes)
+        {
+            if (!_traceQueue)
+            {
+                return;
+            }
+
+            var now = Stopwatch.GetTimestamp();
+            _submissions++;
+            _submittedBytes += bytes;
+            _blockedTicks += now - blockStart;
+            _queuedByteSum += queuedBytes;
+            _minQueuedBytes = Math.Min(_minQueuedBytes, queuedBytes);
+            _maxQueuedBytes = Math.Max(_maxQueuedBytes, queuedBytes);
+            if (dropped)
+            {
+                _drops++;
+            }
+
+            if (queuedBytes == 0)
+            {
+                _emptyObservations++;
+            }
+
+            var elapsedTicks = now - _windowStart;
+            if (elapsedTicks < Stopwatch.Frequency)
+            {
+                return;
+            }
+
+            _windowStart = now;
+            var seconds = elapsedTicks / (double)Stopwatch.Frequency;
+            var bytesPerSecond = (double)_bytesPerFrame * _sampleRate;
+            Console.Error.WriteLine(
+                $"[PERF][AUDIO] stream#{_streamId} {seconds:F1}s " +
+                $"queued_ms min={ToMilliseconds(_minQueuedBytes, bytesPerSecond):F0} " +
+                $"avg={ToMilliseconds((int)(_queuedByteSum / Math.Max(1, _submissions)), bytesPerSecond):F0} " +
+                $"max={ToMilliseconds(_maxQueuedBytes, bytesPerSecond):F0} " +
+                $"cap={ToMilliseconds(_maximumQueuedBytes, bytesPerSecond):F0} " +
+                $"submits/s={_submissions / seconds:F0} " +
+                $"fill={_submittedBytes / seconds / bytesPerSecond * 100.0:F0}% " +
+                $"blocked={_blockedTicks * 100.0 / elapsedTicks:F0}% " +
+                $"empty={_emptyObservations} drops={_drops}");
+
+            _submissions = 0;
+            _submittedBytes = 0;
+            _blockedTicks = 0;
+            _drops = 0;
+            _emptyObservations = 0;
+            _minQueuedBytes = int.MaxValue;
+            _maxQueuedBytes = 0;
+            _queuedByteSum = 0;
+        }
+
+        private static double ToMilliseconds(int bytes, double bytesPerSecond) =>
+            bytesPerSecond <= 0 ? 0 : bytes / bytesPerSecond * 1000.0;
+
+        public void Dispose()
+        {
+            lock (_gate)
+            {
+                if (_disposed)
+                {
+                    return;
+                }
+
+                _disposed = true;
+                if (_stream is not null)
+                {
+                    SDL_ClearAudioStream(_stream);
+                    SDL_DestroyAudioStream(_stream);
+                    _stream = null;
+                }
+            }
+        }
+    }
+}

src/SharpEmu.LibAtrac9/Atrac9Config.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System.IO;
 using LibAtrac9.Utilities;

src/SharpEmu.LibAtrac9/Atrac9Decoder.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using LibAtrac9.Utilities;

src/SharpEmu.LibAtrac9/Atrac9Rng.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {

src/SharpEmu.LibAtrac9/BandExtension.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 

src/SharpEmu.LibAtrac9/BitAllocation.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 

src/SharpEmu.LibAtrac9/Block.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {

src/SharpEmu.LibAtrac9/Channel.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using LibAtrac9.Utilities;
 

src/SharpEmu.LibAtrac9/ChannelConfig.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {

src/SharpEmu.LibAtrac9/Frame.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {

src/SharpEmu.LibAtrac9/HuffmanCodebook.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using LibAtrac9.Utilities;

src/SharpEmu.LibAtrac9/HuffmanCodebooks.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {
@@ -1350,4 +1351,4 @@ namespace LibAtrac9
             new byte[] {0, 0, 0, 0}
         };
     }
-}
+}

src/SharpEmu.LibAtrac9/Quantization.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 

src/SharpEmu.LibAtrac9/ScaleFactors.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using System.IO;

src/SharpEmu.LibAtrac9/SharpEmu.LibAtrac9.csproj

@@ -0,0 +1,12 @@
+<!--
+Copyright (C) 2018 VGMToolbox Project
+SPDX-License-Identifier: MIT
+-->
+
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <AssemblyName>SharpEmu.LibAtrac9</AssemblyName>
+    <RootNamespace>LibAtrac9</RootNamespace>
+    <GenerateDocumentationFile>false</GenerateDocumentationFile>
+  </PropertyGroup>
+</Project>

src/SharpEmu.LibAtrac9/Stereo.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9
 {

src/SharpEmu.LibAtrac9/Tables.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using static LibAtrac9.HuffmanCodebooks;

src/SharpEmu.LibAtrac9/Unpack.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using System.IO;

src/SharpEmu.LibAtrac9/Utilities/Bit.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 namespace LibAtrac9.Utilities
 {

src/SharpEmu.LibAtrac9/Utilities/BitReader.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using System.Diagnostics;

src/SharpEmu.LibAtrac9/Utilities/Helpers.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System.Runtime.CompilerServices;
 

src/SharpEmu.LibAtrac9/Utilities/Mdct.cs

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #nullable disable
 using System;
 using System.Collections.Generic;

src/SharpEmu.Libs/Acm/AcmExports.cs

@@ -2,13 +2,17 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 using System.Buffers.Binary;
+using System.Collections.Concurrent;
 using SharpEmu.HLE;
 
 namespace SharpEmu.Libs.Acm;
 
 public static class AcmExports
 {
+    private const int AcmBatchErrorBytes = 32;
+    private static readonly ConcurrentDictionary<uint, byte> Contexts = new();
     private static int _nextContextHandle;
+    private static int _nextBatchHandle;
 
     [SysAbiExport(
         Nid = "ZIXln2K3XMk",
@@ -23,12 +27,17 @@ public static class AcmExports
             return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
         }
 
-        var handle = (ulong)Interlocked.Increment(ref _nextContextHandle);
+        var handle = unchecked((uint)Interlocked.Increment(ref _nextContextHandle));
-        Span<byte> handleBytes = stackalloc byte[sizeof(ulong)];
+        Span<byte> handleBytes = stackalloc byte[sizeof(uint)];
-        BinaryPrimitives.WriteUInt64LittleEndian(handleBytes, handle);
+        BinaryPrimitives.WriteUInt32LittleEndian(handleBytes, handle);
-        return ctx.Memory.TryWrite(outContextAddress, handleBytes)
+        if (!ctx.Memory.TryWrite(outContextAddress, handleBytes))
-            ? ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK)
+        {
-            : ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+        }
+
+        Contexts[handle] = 0;
+        Trace($"context_create context={handle}");
+        return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK);
     }
 
     [SysAbiExport(
@@ -38,7 +47,196 @@ public static class AcmExports
         LibraryName = "libSceAcm")]
     public static int AcmContextDestroy(CpuContext ctx)
     {
-        _ = ctx;
+        var context = unchecked((uint)ctx[CpuRegister.Rdi]);
+        Contexts.TryRemove(context, out _);
+        Trace($"context_destroy context={context}");
         return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK);
     }
+
+    [SysAbiExport(
+        Nid = "tW9W+CAG4FE",
+        ExportName = "sceAcmBatchStartBuffer",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmBatchStartBuffer(CpuContext ctx)
+    {
+        var context = unchecked((uint)ctx[CpuRegister.Rdi]);
+        var commandsAddress = ctx[CpuRegister.Rsi];
+        var commandsSize = ctx[CpuRegister.Rdx];
+        var errorAddress = ctx[CpuRegister.Rcx];
+        var batchAddress = ctx[CpuRegister.R8];
+
+        if (!Contexts.ContainsKey(context) ||
+            batchAddress == 0 ||
+            (commandsSize != 0 && commandsAddress == 0))
+        {
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
+        }
+
+        return CompleteBatchStart(ctx, context, 1, errorAddress, batchAddress);
+    }
+
+    [SysAbiExport(
+        Nid = "8fe55ktlNVo",
+        ExportName = "sceAcmBatchStartBuffers",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmBatchStartBuffers(CpuContext ctx)
+    {
+        var context = unchecked((uint)ctx[CpuRegister.Rdi]);
+        var infoCount = unchecked((uint)ctx[CpuRegister.Rsi]);
+        var infoArrayAddress = ctx[CpuRegister.Rdx];
+        var errorAddress = ctx[CpuRegister.Rcx];
+        var batchAddress = ctx[CpuRegister.R8];
+
+        if (!Contexts.ContainsKey(context) ||
+            batchAddress == 0 ||
+            (infoCount != 0 && infoArrayAddress == 0))
+        {
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
+        }
+
+        return CompleteBatchStart(ctx, context, infoCount, errorAddress, batchAddress);
+    }
+
+    [SysAbiExport(
+        Nid = "RLN3gRlXJLE",
+        ExportName = "sceAcmBatchWait",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmBatchWait(CpuContext ctx)
+    {
+        var context = unchecked((uint)ctx[CpuRegister.Rdi]);
+        return ctx.SetReturn(
+            Contexts.ContainsKey(context)
+                ? OrbisGen2Result.ORBIS_GEN2_OK
+                : OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
+    }
+
+    [SysAbiExport(
+        Nid = "r7z5YQFZo+U",
+        ExportName = "sceAcmBatchJobNotification",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmBatchJobNotification(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 32);
+
+    [SysAbiExport(
+        Nid = "u70oWo92SYQ",
+        ExportName = "sceAcm_ConvReverb_SharedInput",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmConvReverbSharedInput(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 1024);
+
+    [SysAbiExport(
+        Nid = "9nLbWmRDpa8",
+        ExportName = "sceAcm_ConvReverb_SharedIr",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmConvReverbSharedIr(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 1024);
+
+    [SysAbiExport(
+        Nid = "KovqaFbmtsM",
+        ExportName = "sceAcm_FFT",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmFft(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 256);
+
+    [SysAbiExport(
+        Nid = "DR-ZCmvVR9Q",
+        ExportName = "sceAcm_IFFT",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmIfft(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 256);
+
+    [SysAbiExport(
+        Nid = "LA4RCNKnFjg",
+        ExportName = "sceAcm_Panner",
+        Target = Generation.Gen4 | Generation.Gen5,
+        LibraryName = "libSceAcm")]
+    public static int AcmPanner(CpuContext ctx) =>
+        AdvanceBatchInfo(ctx, 512);
+
+    internal static void ResetForTests()
+    {
+        Contexts.Clear();
+        Interlocked.Exchange(ref _nextContextHandle, 0);
+        Interlocked.Exchange(ref _nextBatchHandle, 0);
+    }
+
+    private static int CompleteBatchStart(
+        CpuContext ctx,
+        uint context,
+        uint infoCount,
+        ulong errorAddress,
+        ulong batchAddress)
+    {
+        if (errorAddress != 0)
+        {
+            Span<byte> error = stackalloc byte[AcmBatchErrorBytes];
+            error.Clear();
+            if (!ctx.Memory.TryWrite(errorAddress, error))
+            {
+                return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+            }
+        }
+
+        var batch = unchecked((uint)Interlocked.Increment(ref _nextBatchHandle));
+        Span<byte> batchBytes = stackalloc byte[sizeof(uint)];
+        BinaryPrimitives.WriteUInt32LittleEndian(batchBytes, batch);
+        if (!ctx.Memory.TryWrite(batchAddress, batchBytes))
+        {
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+        }
+
+        Trace($"batch_start context={context} count={infoCount} batch={batch}");
+        return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK);
+    }
+
+    private static int AdvanceBatchInfo(CpuContext ctx, ulong byteCount)
+    {
+        var infoAddress = ctx[CpuRegister.Rdi];
+        if (infoAddress == 0)
+        {
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK);
+        }
+
+        Span<byte> info = stackalloc byte[24];
+        if (!ctx.Memory.TryRead(infoAddress, info))
+        {
+            return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+        }
+
+        var buffer = BinaryPrimitives.ReadUInt64LittleEndian(info);
+        var offset = BinaryPrimitives.ReadUInt64LittleEndian(info[8..]);
+        var size = BinaryPrimitives.ReadUInt64LittleEndian(info[16..]);
+        if (buffer != 0 && size != 0)
+        {
+            var nextOffset = offset > ulong.MaxValue - byteCount
+                ? ulong.MaxValue
+                : offset + byteCount;
+            BinaryPrimitives.WriteUInt64LittleEndian(info[8..], Math.Min(size, nextOffset));
+            if (!ctx.Memory.TryWrite(infoAddress, info))
+            {
+                return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_ERROR_MEMORY_FAULT);
+            }
+        }
+
+        return ctx.SetReturn(OrbisGen2Result.ORBIS_GEN2_OK);
+    }
+
+    private static void Trace(string message)
+    {
+        if (string.Equals(
+                Environment.GetEnvironmentVariable("SHARPEMU_LOG_ACM"),
+                "1",
+                StringComparison.Ordinal))
+        {
+            Console.Error.WriteLine($"[LOADER][TRACE] acm.{message}");
+        }
+    }
 }

src/SharpEmu.Libs/Audio/Atrac9DecodeState.cs

@@ -0,0 +1,409 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Buffers.Binary;
+using LibAtrac9;
+
+namespace SharpEmu.Libs.Audio;
+
+internal enum Atrac9PcmEncoding
+{
+    Signed16,
+    Signed32,
+    Float,
+}
+
+internal readonly record struct Atrac9DecodeResult(
+    int Status,
+    int InputConsumed,
+    int OutputWritten,
+    ulong TotalDecodedSamples,
+    uint Frames);
+
+internal sealed class Atrac9DecodeState
+{
+    internal const int ResultNotInitialized = 0x00000001;
+    internal const int ResultInvalidData = 0x00000002;
+    internal const int ResultInvalidParameter = 0x00000004;
+    internal const int ResultPartialInput = 0x00000008;
+    internal const int ResultNotEnoughRoom = 0x00000010;
+    internal const int ResultCodecError = 0x40000000;
+
+    private const int MaxContainerHeaderBytes = 8 * 1024;
+
+    private enum ContainerScan
+    {
+        NotContainer,
+        NeedMoreData,
+        Found,
+    }
+
+    private readonly object _gate = new();
+    private Atrac9Decoder? _decoder;
+    private byte[]? _configData;
+    private byte[]? _compressed;
+    private short[][]? _planarPcm;
+    private byte[]? _containerHeader;
+    private int _containerHeaderLength;
+    private int _compressedLength;
+    private ulong _totalDecodedSamples;
+
+    public Atrac9Config? Config
+    {
+        get
+        {
+            lock (_gate)
+            {
+                return _decoder?.Config;
+            }
+        }
+    }
+
+    public bool TryInitialize(ReadOnlySpan<byte> configData)
+    {
+        if (configData.Length < 4)
+        {
+            return false;
+        }
+
+        lock (_gate)
+        {
+            try
+            {
+                var normalizedConfig = configData[..4].ToArray();
+                var decoder = new Atrac9Decoder();
+                decoder.Initialize(normalizedConfig);
+                var config = decoder.Config;
+
+                _decoder = decoder;
+                _configData = normalizedConfig;
+                _compressed = new byte[config.SuperframeBytes];
+                _planarPcm = CreatePcmBuffer(config.ChannelCount, config.SuperframeSamples);
+                _compressedLength = 0;
+                _totalDecodedSamples = 0;
+                _containerHeaderLength = 0;
+                Trace(
+                    $"initialized config={Convert.ToHexString(normalizedConfig)} channels={config.ChannelCount} " +
+                    $"rate={config.SampleRate} frame_samples={config.FrameSamples} " +
+                    $"superframe_samples={config.SuperframeSamples} superframe_bytes={config.SuperframeBytes} " +
+                    $"frames_per_superframe={config.FramesPerSuperframe}");
+                return true;
+            }
+            catch (Exception exception) when (
+                exception is ArgumentException or InvalidDataException or InvalidOperationException)
+            {
+                Clear();
+                return false;
+            }
+        }
+    }
+
+    public void Reset()
+    {
+        lock (_gate)
+        {
+            if (_configData is null)
+            {
+                Clear();
+                return;
+            }
+
+            var decoder = new Atrac9Decoder();
+            decoder.Initialize((byte[])_configData.Clone());
+            _decoder = decoder;
+            _compressedLength = 0;
+            _totalDecodedSamples = 0;
+            _containerHeaderLength = 0;
+            if (_compressed is not null)
+            {
+                Array.Clear(_compressed);
+            }
+        }
+    }
+
+    public Atrac9DecodeResult Decode(
+        ReadOnlySpan<byte> input,
+        Span<byte> output,
+        Atrac9PcmEncoding encoding,
+        int requestedChannels,
+        bool multipleFrames)
+    {
+        lock (_gate)
+        {
+            if (_decoder is null || _compressed is null || _planarPcm is null)
+            {
+                return new Atrac9DecodeResult(
+                    ResultNotInitialized,
+                    0,
+                    0,
+                    _totalDecodedSamples,
+                    0);
+            }
+
+            var config = _decoder.Config;
+            var channels = requestedChannels > 0 ? requestedChannels : config.ChannelCount;
+            if (channels is < 1 or > 16)
+            {
+                return new Atrac9DecodeResult(
+                    ResultInvalidParameter,
+                    0,
+                    0,
+                    _totalDecodedSamples,
+                    0);
+            }
+
+            var bytesPerSample = GetBytesPerSample(encoding);
+            var outputBytesPerSuperframe = checked(config.SuperframeSamples * channels * bytesPerSample);
+            var consumed = 0;
+            var written = 0;
+            uint frames = 0;
+            var status = 0;
+
+            while (_compressedLength == config.SuperframeBytes ||
+                   consumed < input.Length)
+            {
+                // Titles that stream whole .at9 files hand AJM the RIFF/WAVE
+                // container rather than a pointer into its `data` chunk, so the
+                // stream has to be advanced past the header before the first
+                // superframe — otherwise every job fails with invalid data and
+                // the title drops the voice. This is checked at every superframe
+                // boundary, not just after initialize, because a looping voice
+                // rewinds to the file header without reinitialising.
+                if (_compressedLength == 0 && (_containerHeaderLength != 0 || consumed < input.Length))
+                {
+                    var scan = ScanContainerHeader(input[consumed..], out var headerBytes);
+                    if (scan == ContainerScan.NeedMoreData)
+                    {
+                        consumed = input.Length;
+                        status |= ResultPartialInput;
+                        break;
+                    }
+
+                    if (scan == ContainerScan.Found)
+                    {
+                        _containerHeader = null;
+                        _containerHeaderLength = 0;
+                        consumed += headerBytes;
+                        continue;
+                    }
+                }
+
+                if (_compressedLength < config.SuperframeBytes)
+                {
+                    var copied = Math.Min(config.SuperframeBytes - _compressedLength, input.Length - consumed);
+                    input.Slice(consumed, copied).CopyTo(_compressed.AsSpan(_compressedLength));
+                    _compressedLength += copied;
+                    consumed += copied;
+                }
+
+                if (_compressedLength < config.SuperframeBytes)
+                {
+                    status |= ResultPartialInput;
+                    break;
+                }
+
+                if (output.Length - written < outputBytesPerSuperframe)
+                {
+                    status |= ResultNotEnoughRoom;
+                    break;
+                }
+
+                try
+                {
+                    _decoder.Decode(_compressed, _planarPcm);
+                }
+                catch (Exception exception) when (
+                    exception is ArgumentException or InvalidDataException or InvalidOperationException or IndexOutOfRangeException)
+                {
+                    Trace(
+                        $"decode_failed superframe_bytes={config.SuperframeBytes} " +
+                        $"config={Convert.ToHexString(_configData ?? [])} " +
+                        $"head={Convert.ToHexString(_compressed.AsSpan(0, Math.Min(16, _compressed.Length)))} " +
+                        $"error={exception.GetType().Name}: {exception.Message}");
+                    _compressedLength = 0;
+                    return new Atrac9DecodeResult(
+                        status | ResultInvalidData | ResultCodecError,
+                        consumed,
+                        written,
+                        _totalDecodedSamples,
+                        frames);
+                }
+
+                WriteInterleaved(
+                    _planarPcm,
+                    output.Slice(written, outputBytesPerSuperframe),
+                    config.SuperframeSamples,
+                    channels,
+                    encoding);
+
+                written += outputBytesPerSuperframe;
+                _compressedLength = 0;
+                _totalDecodedSamples += unchecked((uint)config.SuperframeSamples);
+                frames += unchecked((uint)config.FramesPerSuperframe);
+
+                if (!multipleFrames)
+                {
+                    break;
+                }
+            }
+
+            return new Atrac9DecodeResult(
+                status,
+                consumed,
+                written,
+                _totalDecodedSamples,
+                frames);
+        }
+    }
+
+    private ContainerScan ScanContainerHeader(ReadOnlySpan<byte> input, out int inputHeaderBytes)
+    {
+        inputHeaderBytes = 0;
+
+        if (_containerHeaderLength == 0 &&
+            (input.Length < 4 || !input[..4].SequenceEqual("RIFF"u8)))
+        {
+            return ContainerScan.NotContainer;
+        }
+
+        _containerHeader ??= new byte[MaxContainerHeaderBytes];
+        var previousLength = _containerHeaderLength;
+        var copied = Math.Min(input.Length, MaxContainerHeaderBytes - previousLength);
+        input[..copied].CopyTo(_containerHeader.AsSpan(previousLength));
+        var totalLength = previousLength + copied;
+
+        if (!TryFindRiffDataOffset(_containerHeader.AsSpan(0, totalLength), out var dataOffset))
+        {
+            if (totalLength >= MaxContainerHeaderBytes)
+            {
+                // Not a shape we understand — fall back to treating the stream
+                // as raw superframes rather than swallowing it forever. The
+                // scratch is dropped without advancing the caller's cursor, so
+                // the bytes are still decoded normally.
+                Trace($"container_scan_gave_up bytes={totalLength}");
+                _containerHeader = null;
+                _containerHeaderLength = 0;
+                return ContainerScan.NotContainer;
+            }
+
+            _containerHeaderLength = totalLength;
+            return ContainerScan.NeedMoreData;
+        }
+
+        inputHeaderBytes = dataOffset - previousLength;
+        Trace($"container_header_skipped bytes={dataOffset} from_this_input={inputHeaderBytes}");
+        return ContainerScan.Found;
+    }
+
+    private static bool TryFindRiffDataOffset(ReadOnlySpan<byte> header, out int dataOffset)
+    {
+        dataOffset = 0;
+        if (header.Length < 12 ||
+            !header[..4].SequenceEqual("RIFF"u8) ||
+            !header.Slice(8, 4).SequenceEqual("WAVE"u8))
+        {
+            return false;
+        }
+
+        var offset = 12;
+        while (offset + 8 <= header.Length)
+        {
+            var chunkId = header.Slice(offset, 4);
+            var chunkSize = BinaryPrimitives.ReadUInt32LittleEndian(header.Slice(offset + 4, 4));
+            offset += 8;
+            if (chunkId.SequenceEqual("data"u8))
+            {
+                dataOffset = offset;
+                return true;
+            }
+
+            // RIFF chunks are word aligned.
+            var advance = chunkSize + (chunkSize & 1);
+            if (advance > (ulong)(int.MaxValue - offset))
+            {
+                return false;
+            }
+
+            offset += (int)advance;
+        }
+
+        return false;
+    }
+
+    private static short[][] CreatePcmBuffer(int channels, int samples)
+    {
+        var result = new short[channels][];
+        for (var channel = 0; channel < channels; channel++)
+        {
+            result[channel] = new short[samples];
+        }
+
+        return result;
+    }
+
+    private static int GetBytesPerSample(Atrac9PcmEncoding encoding) =>
+        encoding switch
+        {
+            Atrac9PcmEncoding.Signed16 => sizeof(short),
+            Atrac9PcmEncoding.Signed32 => sizeof(int),
+            Atrac9PcmEncoding.Float => sizeof(float),
+            _ => throw new ArgumentOutOfRangeException(nameof(encoding)),
+        };
+
+    private static void WriteInterleaved(
+        short[][] source,
+        Span<byte> destination,
+        int samples,
+        int channels,
+        Atrac9PcmEncoding encoding)
+    {
+        var offset = 0;
+        for (var sample = 0; sample < samples; sample++)
+        {
+            for (var channel = 0; channel < channels; channel++)
+            {
+                var sourceChannel = Math.Min(channel, source.Length - 1);
+                var value = source[sourceChannel][sample];
+                switch (encoding)
+                {
+                    case Atrac9PcmEncoding.Signed16:
+                        BinaryPrimitives.WriteInt16LittleEndian(destination[offset..], value);
+                        offset += sizeof(short);
+                        break;
+                    case Atrac9PcmEncoding.Signed32:
+                        BinaryPrimitives.WriteInt32LittleEndian(destination[offset..], value << 16);
+                        offset += sizeof(int);
+                        break;
+                    case Atrac9PcmEncoding.Float:
+                        BinaryPrimitives.WriteInt32LittleEndian(
+                            destination[offset..],
+                            BitConverter.SingleToInt32Bits(value / 32768.0f));
+                        offset += sizeof(float);
+                        break;
+                    default:
+                        throw new ArgumentOutOfRangeException(nameof(encoding));
+                }
+            }
+        }
+    }
+
+    private static void Trace(string message)
+    {
+        if (string.Equals(Environment.GetEnvironmentVariable("SHARPEMU_LOG_AJM"), "1", StringComparison.Ordinal))
+        {
+            Console.Error.WriteLine($"[LOADER][TRACE] ajm.at9.{message}");
+        }
+    }
+
+    private void Clear()
+    {
+        _decoder = null;
+        _configData = null;
+        _compressed = null;
+        _planarPcm = null;
+        _containerHeader = null;
+        _containerHeaderLength = 0;
+        _compressedLength = 0;
+        _totalDecodedSamples = 0;
+    }
+}

src/SharpEmu.Libs/Audio/AudioOutExports.cs

@@ -44,6 +44,7 @@ public static class AudioOutExports
             int channels,
             int bytesPerSample,
             bool isFloat,
+            bool preservesGuestFormat,
             IHostAudioStream? backend)
         {
             UserId = userId;
@@ -54,6 +55,7 @@ public static class AudioOutExports
             Channels = channels;
             BytesPerSample = bytesPerSample;
             IsFloat = isFloat;
+            PreservesGuestFormat = preservesGuestFormat;
             Backend = backend;
         }
 
@@ -65,6 +67,7 @@ public static class AudioOutExports
         public int Channels { get; }
         public int BytesPerSample { get; }
         public bool IsFloat { get; }
+        public bool PreservesGuestFormat { get; }
         public IHostAudioStream? Backend { get; }
         public object SubmissionGate { get; } = new();
         public volatile float Volume = 1.0f;
@@ -140,6 +143,7 @@ public static class AudioOutExports
         }
 
         IHostAudioStream? backend = null;
+        var preservesGuestFormat = false;
         string backendName;
         try
         {
@@ -152,7 +156,18 @@ public static class AudioOutExports
             else
             {
                 var audio = HostPlatform.Current.Audio;
-                backend = audio.OpenStereoPcm16Stream(frequency);
+                if (audio is IHostPcmAudioOutput pcmAudio)
+                {
+                    backend = pcmAudio.OpenPcmStream(
+                        frequency,
+                        channels,
+                        isFloat ? HostPcmFormat.Float32 : HostPcmFormat.Signed16);
+                    preservesGuestFormat = true;
+                }
+                else
+                {
+                    backend = audio.OpenStereoPcm16Stream(frequency);
+                }
                 backendName = audio.BackendName;
             }
         }
@@ -173,6 +188,7 @@ public static class AudioOutExports
             channels,
             bytesPerSample,
             isFloat,
+            preservesGuestFormat,
             backend);
         Console.Error.WriteLine(
             $"[LOADER][INFO] AudioOut port {handle}: {frequency} Hz, " +
@@ -321,18 +337,13 @@ public static class AudioOutExports
                 return ctx.SetReturn(0);
             }
 
-            var outputLength = checked((int)port.BufferLength * AudioPcmConversion.OutputFrameSize);
+            var outputLength = port.PreservesGuestFormat
+                ? port.BufferByteLength
+                : checked((int)port.BufferLength * AudioPcmConversion.OutputFrameSize);
             var output = ArrayPool<byte>.Shared.Rent(outputLength);
             try
             {
-                AudioPcmConversion.ConvertToStereoPcm16(
+                ConvertForHost(port, source, output.AsSpan(0, outputLength));
-                    source,
-                    output.AsSpan(0, outputLength),
-                    checked((int)port.BufferLength),
-                    port.Channels,
-                    port.BytesPerSample,
-                    port.IsFloat,
-                    port.Volume);
                 if (!port.Backend.Submit(output.AsSpan(0, outputLength)))
                 {
                     port.PaceSilence();
@@ -449,17 +460,11 @@ public static class AudioOutExports
 
                     TraceOutput(output.Handle, output.Port, source);
 
-                    output.HostBufferLength = checked(
+                    output.HostBufferLength = output.Port.PreservesGuestFormat
-                        (int)output.Port.BufferLength * AudioPcmConversion.OutputFrameSize);
+                        ? output.Port.BufferByteLength
+                        : checked((int)output.Port.BufferLength * AudioPcmConversion.OutputFrameSize);
                     output.HostBuffer = ArrayPool<byte>.Shared.Rent(output.HostBufferLength);
-                    AudioPcmConversion.ConvertToStereoPcm16(
+                    ConvertForHost(output.Port, source, output.HostBuffer.AsSpan(0, output.HostBufferLength));
-                        source,
-                        output.HostBuffer.AsSpan(0, output.HostBufferLength),
-                        checked((int)output.Port.BufferLength),
-                        output.Port.Channels,
-                        output.Port.BytesPerSample,
-                        output.Port.IsFloat,
-                        output.Port.Volume);
                 }
                 finally
                 {
@@ -513,6 +518,24 @@ public static class AudioOutExports
         (ulong)candidate.BufferLength * current.Frequency >
         (ulong)current.BufferLength * candidate.Frequency;
 
+    private static void ConvertForHost(PortState port, ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        if (port.PreservesGuestFormat)
+        {
+            AudioPcmConversion.CopyWithVolume(source, destination, port.IsFloat, port.Volume);
+            return;
+        }
+
+        AudioPcmConversion.ConvertToStereoPcm16(
+            source,
+            destination,
+            checked((int)port.BufferLength),
+            port.Channels,
+            port.BytesPerSample,
+            port.IsFloat,
+            port.Volume);
+    }
+
     private static void TraceOutput(int handle, PortState port, ReadOnlySpan<byte> source)
     {
         if (!_traceOutput)

src/SharpEmu.Libs/Audio/AudioPcmConversion.cs

@@ -43,6 +43,46 @@ internal static class AudioPcmConversion
         }
     }
 
+    /// <summary>
+    /// Copies interleaved PCM without changing its channel layout. SDL can convert
+    /// this directly to the physical device, which preserves surround mixes that
+    /// would otherwise be truncated to the first two guest channels.
+    /// </summary>
+    public static void CopyWithVolume(
+        ReadOnlySpan<byte> source,
+        Span<byte> destination,
+        bool isFloat,
+        float volume)
+    {
+        var clampedVolume = Math.Clamp(volume, 0.0f, 1.0f);
+        if (clampedVolume >= 1.0f)
+        {
+            source.CopyTo(destination);
+            return;
+        }
+
+        if (isFloat)
+        {
+            for (var offset = 0; offset < source.Length; offset += sizeof(float))
+            {
+                var sample = BinaryPrimitives.ReadSingleLittleEndian(source.Slice(offset, sizeof(float)));
+                BinaryPrimitives.WriteSingleLittleEndian(
+                    destination.Slice(offset, sizeof(float)),
+                    sample * clampedVolume);
+            }
+
+            return;
+        }
+
+        for (var offset = 0; offset < source.Length; offset += sizeof(short))
+        {
+            var sample = BinaryPrimitives.ReadInt16LittleEndian(source.Slice(offset, sizeof(short)));
+            BinaryPrimitives.WriteInt16LittleEndian(
+                destination.Slice(offset, sizeof(short)),
+                ApplyVolume(sample, clampedVolume));
+        }
+    }
+
     private static short ReadSample(
         ReadOnlySpan<byte> frame,
         int channel,

src/SharpEmu.Libs/Codec/CodecExports.cs

@@ -2,28 +2,84 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 using SharpEmu.HLE;
+using SharpEmu.Libs.Audio;
 using SharpEmu.Libs.Kernel;
+using System.Buffers;
+using System.Buffers.Binary;
 using System.Collections.Concurrent;
 using System.Threading;
 
 namespace SharpEmu.Libs.Codec;
 
 /// <summary>
-/// libSceVideodec / libSceAudiodec handle management. Actual H.264/HEVC and
+/// libSceVideodec / libSceAudiodec compatibility exports.
-/// AAC/AT9 decoding requires an external codec, which is out of scope; these
-/// exports keep the decoder lifecycle resolvable (create/decode/flush/delete)
-/// and report "no output produced" so guests advance instead of failing on
-/// unresolved imports.
 /// </summary>
 public static class CodecExports
 {
     private const int Ok = 0;
     private const int VideodecErrorInvalidArg = unchecked((int)0x80620801);
+    private const int AudiodecErrorInvalidType = unchecked((int)0x807F0001);
     private const int AudiodecErrorInvalidArg = unchecked((int)0x807F0002);
+    private const int AudiodecErrorInvalidParamSize = unchecked((int)0x807F0004);
+    private const int AudiodecErrorInvalidBsiInfoSize = unchecked((int)0x807F0005);
+    private const int AudiodecErrorInvalidAuInfoSize = unchecked((int)0x807F0006);
+    private const int AudiodecErrorInvalidPcmItemSize = unchecked((int)0x807F0007);
+    private const int AudiodecErrorInvalidCtrlPointer = unchecked((int)0x807F0008);
+    private const int AudiodecErrorInvalidParamPointer = unchecked((int)0x807F0009);
+    private const int AudiodecErrorInvalidBsiInfoPointer = unchecked((int)0x807F000A);
+    private const int AudiodecErrorInvalidAuInfoPointer = unchecked((int)0x807F000B);
+    private const int AudiodecErrorInvalidPcmItemPointer = unchecked((int)0x807F000C);
+    private const int AudiodecErrorInvalidAuPointer = unchecked((int)0x807F000D);
+    private const int AudiodecErrorInvalidPcmPointer = unchecked((int)0x807F000E);
+    private const int AudiodecErrorInvalidHandle = unchecked((int)0x807F000F);
+    private const int AudiodecErrorInvalidWordLength = unchecked((int)0x807F0010);
+    private const int AudiodecErrorInvalidAuSize = unchecked((int)0x807F0011);
+    private const int AudiodecErrorInvalidPcmSize = unchecked((int)0x807F0012);
+    private const uint AudiodecTypeAt9 = 1;
+    private const uint AudiodecTypeMp3 = 2;
+    private const uint AudiodecTypeAac = 3;
+    private const int MaxAudioDecoders = 64;
+    private const int MaxDecodeBufferBytes = 64 * 1024 * 1024;
 
     private static readonly ConcurrentDictionary<ulong, byte> VideoDecoders = new();
-    private static readonly ConcurrentDictionary<ulong, byte> AudioDecoders = new();
+    private static readonly ConcurrentDictionary<int, AudioDecoderState> AudioDecoders = new();
+    private static readonly ConcurrentDictionary<uint, int> AudioCodecInitCounts = new();
+    private static readonly object AudioDecoderGate = new();
     private static long _nextHandle = 1;
+    private static int _nextAudioHandle;
+
+    private sealed class AudioDecoderState
+    {
+        public required uint CodecType { get; init; }
+
+        public required int WordSize { get; init; }
+
+        public required int Channels { get; init; }
+
+        public required int SampleRate { get; init; }
+
+        public required int FrameBytes { get; init; }
+
+        public required int FramesPerSuperframe { get; init; }
+
+        public required int FrameSamples { get; init; }
+
+        public Atrac9DecodeState? Atrac9 { get; init; }
+    }
+
+    private readonly record struct AudioControl(
+        ulong ParamAddress,
+        ulong BsiInfoAddress,
+        ulong AuInfoAddress,
+        ulong PcmItemAddress,
+        ulong AuAddress,
+        uint AuSize,
+        ulong PcmAddress,
+        uint PcmSize,
+        int WordSize,
+        byte[]? Atrac9Config,
+        uint AacMaxChannels,
+        uint AacSampleRateIndex);
 
     // ---- Video decoder ----
 
@@ -65,34 +121,572 @@ public static class CodecExports
 
     // ---- Audio decoder ----
 
+    [SysAbiExport(Nid = "VjhsmxpcezI", ExportName = "sceAudiodecInitLibrary",
+        Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
+    public static int AudiodecInitLibrary(CpuContext ctx)
+    {
+        var codecType = unchecked((uint)ctx[CpuRegister.Rdi]);
+        if (!IsValidAudioCodecType(codecType))
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidType);
+        }
+
+        AudioCodecInitCounts.AddOrUpdate(codecType, 1, static (_, count) => count + 1);
+        return SetReturn(ctx, Ok);
+    }
+
+    [SysAbiExport(Nid = "h5jSB2QIDV0", ExportName = "sceAudiodecTermLibrary",
+        Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
+    public static int AudiodecTermLibrary(CpuContext ctx)
+    {
+        var codecType = unchecked((uint)ctx[CpuRegister.Rdi]);
+        if (!IsValidAudioCodecType(codecType))
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidType);
+        }
+
+        AudioCodecInitCounts.AddOrUpdate(codecType, 0, static (_, count) => Math.Max(0, count - 1));
+        return SetReturn(ctx, Ok);
+    }
+
     [SysAbiExport(Nid = "O3f1sLMWRvs", ExportName = "sceAudiodecCreateDecoder",
         Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
     public static int AudiodecCreateDecoder(CpuContext ctx)
     {
-        var handle = (ulong)Interlocked.Increment(ref _nextHandle);
+        var controlAddress = ctx[CpuRegister.Rdi];
-        AudioDecoders[handle] = 1;
+        var codecType = unchecked((uint)ctx[CpuRegister.Rsi]);
-        // sceAudiodec returns the handle directly (>= 0) or a negative error.
+        if (!IsValidAudioCodecType(codecType))
-        ctx[CpuRegister.Rax] = handle;
+        {
-        return unchecked((int)handle);
+            return SetReturn(ctx, AudiodecErrorInvalidType);
+        }
+
+        var validation = TryReadAudioControl(ctx, controlAddress, codecType, decode: false, out var control);
+        if (validation != Ok)
+        {
+            return SetReturn(ctx, validation);
+        }
+
+        if (!AudioCodecInitCounts.TryGetValue(codecType, out var initCount) || initCount == 0)
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidArg);
+        }
+
+        var decoder = CreateAudioDecoder(codecType, control);
+        if (decoder is null)
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidArg);
+        }
+
+        int handle;
+        lock (AudioDecoderGate)
+        {
+            if (AudioDecoders.Count >= MaxAudioDecoders)
+            {
+                return SetReturn(ctx, AudiodecErrorInvalidArg);
+            }
+
+            do
+            {
+                _nextAudioHandle = _nextAudioHandle % MaxAudioDecoders + 1;
+                handle = _nextAudioHandle;
+            }
+            while (AudioDecoders.ContainsKey(handle));
+
+            AudioDecoders[handle] = decoder;
+        }
+
+        WriteAudioDecoderInfo(ctx, control.BsiInfoAddress, decoder, Ok);
+        return SetReturn(ctx, handle);
     }
 
     [SysAbiExport(Nid = "KHXHMDLkILw", ExportName = "sceAudiodecDecode",
         Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
     public static int AudiodecDecode(CpuContext ctx)
     {
-        // No decoder present: report success with zero output samples so the
+        var handle = unchecked((int)ctx[CpuRegister.Rdi]);
-        // caller treats the frame as silent rather than erroring.
+        if (!AudioDecoders.TryGetValue(handle, out var decoder))
-        return SetReturn(ctx, AudioDecoders.ContainsKey(ctx[CpuRegister.Rdi]) ? Ok : AudiodecErrorInvalidArg);
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidHandle);
+        }
+
+        var validation = TryReadAudioControl(
+            ctx,
+            ctx[CpuRegister.Rsi],
+            decoder.CodecType,
+            decode: true,
+            out var control);
+        if (validation != Ok)
+        {
+            return SetReturn(ctx, validation);
+        }
+
+        if (control.AuSize > MaxDecodeBufferBytes)
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidAuSize);
+        }
+
+        if (control.PcmSize > MaxDecodeBufferBytes)
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidPcmSize);
+        }
+
+        if (decoder.CodecType == AudiodecTypeAt9 && decoder.Atrac9 is not null)
+        {
+            DecodeAtrac9(ctx, decoder, control);
+        }
+        else
+        {
+            DecodeAudioSilence(ctx, decoder, control);
+        }
+
+        return SetReturn(ctx, Ok);
     }
 
     [SysAbiExport(Nid = "Tp+ZEy69mLk", ExportName = "sceAudiodecDeleteDecoder",
         Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
     public static int AudiodecDeleteDecoder(CpuContext ctx)
     {
-        AudioDecoders.TryRemove(ctx[CpuRegister.Rdi], out _);
+        var handle = unchecked((int)ctx[CpuRegister.Rdi]);
+        return SetReturn(
+            ctx,
+            AudioDecoders.TryRemove(handle, out _)
+                ? Ok
+                : AudiodecErrorInvalidHandle);
+    }
+
+    [SysAbiExport(Nid = "6Vf9WTLDoss", ExportName = "sceAudiodecClearContext",
+        Target = Generation.Gen4 | Generation.Gen5, LibraryName = "libSceAudiodec")]
+    public static int AudiodecClearContext(CpuContext ctx)
+    {
+        var handle = unchecked((int)ctx[CpuRegister.Rdi]);
+        if (!AudioDecoders.TryGetValue(handle, out var decoder))
+        {
+            return SetReturn(ctx, AudiodecErrorInvalidHandle);
+        }
+
+        decoder.Atrac9?.Reset();
         return SetReturn(ctx, Ok);
     }
 
+    private static bool IsValidAudioCodecType(uint codecType) =>
+        codecType is AudiodecTypeAt9 or AudiodecTypeMp3 or AudiodecTypeAac;
+
+    private static int TryReadAudioControl(
+        CpuContext ctx,
+        ulong controlAddress,
+        uint codecType,
+        bool decode,
+        out AudioControl control)
+    {
+        control = default;
+        if (controlAddress == 0)
+        {
+            return AudiodecErrorInvalidCtrlPointer;
+        }
+
+        Span<byte> controlData = stackalloc byte[32];
+        if (!ctx.Memory.TryRead(controlAddress, controlData))
+        {
+            return AudiodecErrorInvalidCtrlPointer;
+        }
+
+        var paramAddress = BinaryPrimitives.ReadUInt64LittleEndian(controlData);
+        var bsiInfoAddress = BinaryPrimitives.ReadUInt64LittleEndian(controlData[8..]);
+        var auInfoAddress = BinaryPrimitives.ReadUInt64LittleEndian(controlData[16..]);
+        var pcmItemAddress = BinaryPrimitives.ReadUInt64LittleEndian(controlData[24..]);
+        if (paramAddress == 0)
+        {
+            return AudiodecErrorInvalidParamPointer;
+        }
+
+        if (bsiInfoAddress == 0)
+        {
+            return AudiodecErrorInvalidBsiInfoPointer;
+        }
+
+        if (auInfoAddress == 0)
+        {
+            return AudiodecErrorInvalidAuInfoPointer;
+        }
+
+        if (pcmItemAddress == 0)
+        {
+            return AudiodecErrorInvalidPcmItemPointer;
+        }
+
+        Span<byte> auInfo = stackalloc byte[24];
+        if (!ctx.Memory.TryRead(auInfoAddress, auInfo))
+        {
+            return AudiodecErrorInvalidAuInfoPointer;
+        }
+
+        if (BinaryPrimitives.ReadUInt32LittleEndian(auInfo) != auInfo.Length)
+        {
+            return AudiodecErrorInvalidAuInfoSize;
+        }
+
+        Span<byte> pcmItem = stackalloc byte[24];
+        if (!ctx.Memory.TryRead(pcmItemAddress, pcmItem))
+        {
+            return AudiodecErrorInvalidPcmItemPointer;
+        }
+
+        if (BinaryPrimitives.ReadUInt32LittleEndian(pcmItem) != pcmItem.Length)
+        {
+            return AudiodecErrorInvalidPcmItemSize;
+        }
+
+        var auAddress = BinaryPrimitives.ReadUInt64LittleEndian(auInfo[8..]);
+        var auSize = BinaryPrimitives.ReadUInt32LittleEndian(auInfo[16..]);
+        var pcmAddress = BinaryPrimitives.ReadUInt64LittleEndian(pcmItem[8..]);
+        var pcmSize = BinaryPrimitives.ReadUInt32LittleEndian(pcmItem[16..]);
+        if (decode && auAddress == 0)
+        {
+            return AudiodecErrorInvalidAuPointer;
+        }
+
+        if (decode && pcmAddress == 0)
+        {
+            return AudiodecErrorInvalidPcmPointer;
+        }
+
+        var parameterResult = TryReadAudioParameters(
+            ctx,
+            codecType,
+            paramAddress,
+            bsiInfoAddress,
+            out var wordSize,
+            out var atrac9Config,
+            out var aacMaxChannels,
+            out var aacSampleRateIndex);
+        if (parameterResult != Ok)
+        {
+            return parameterResult;
+        }
+
+        if (decode && auSize == 0)
+        {
+            return AudiodecErrorInvalidAuSize;
+        }
+
+        if (decode && pcmSize == 0)
+        {
+            return AudiodecErrorInvalidPcmSize;
+        }
+
+        control = new AudioControl(
+            paramAddress,
+            bsiInfoAddress,
+            auInfoAddress,
+            pcmItemAddress,
+            auAddress,
+            auSize,
+            pcmAddress,
+            pcmSize,
+            wordSize,
+            atrac9Config,
+            aacMaxChannels,
+            aacSampleRateIndex);
+        return Ok;
+    }
+
+    private static int TryReadAudioParameters(
+        CpuContext ctx,
+        uint codecType,
+        ulong paramAddress,
+        ulong bsiInfoAddress,
+        out int wordSize,
+        out byte[]? atrac9Config,
+        out uint aacMaxChannels,
+        out uint aacSampleRateIndex)
+    {
+        wordSize = 0;
+        atrac9Config = null;
+        aacMaxChannels = 0;
+        aacSampleRateIndex = 0;
+
+        var paramSize = codecType switch
+        {
+            AudiodecTypeAt9 => 12,
+            AudiodecTypeMp3 => 8,
+            AudiodecTypeAac => 24,
+            _ => 0,
+        };
+        var bsiSize = codecType switch
+        {
+            AudiodecTypeAt9 => 36,
+            AudiodecTypeMp3 => 24,
+            AudiodecTypeAac => 20,
+            _ => 0,
+        };
+        if (paramSize == 0 || bsiSize == 0)
+        {
+            return AudiodecErrorInvalidType;
+        }
+
+        Span<byte> param = stackalloc byte[paramSize];
+        if (!ctx.Memory.TryRead(paramAddress, param))
+        {
+            return AudiodecErrorInvalidParamPointer;
+        }
+
+        var suppliedParamSize = BinaryPrimitives.ReadUInt32LittleEndian(param);
+        if (codecType == AudiodecTypeAac
+                ? suppliedParamSize < paramSize
+                : suppliedParamSize != paramSize)
+        {
+            return AudiodecErrorInvalidParamSize;
+        }
+
+        Span<byte> bsi = stackalloc byte[bsiSize];
+        if (!ctx.Memory.TryRead(bsiInfoAddress, bsi))
+        {
+            return AudiodecErrorInvalidBsiInfoPointer;
+        }
+
+        if (BinaryPrimitives.ReadUInt32LittleEndian(bsi) != bsiSize)
+        {
+            return AudiodecErrorInvalidBsiInfoSize;
+        }
+
+        wordSize = BinaryPrimitives.ReadInt32LittleEndian(param[4..]);
+        if (wordSize is < 0 or > 2)
+        {
+            return AudiodecErrorInvalidWordLength;
+        }
+
+        if (codecType == AudiodecTypeAt9)
+        {
+            atrac9Config = param[8..12].ToArray();
+        }
+        else if (codecType == AudiodecTypeAac)
+        {
+            aacSampleRateIndex = BinaryPrimitives.ReadUInt32LittleEndian(param[12..]);
+            aacMaxChannels = BinaryPrimitives.ReadUInt32LittleEndian(param[16..]);
+        }
+
+        return Ok;
+    }
+
+    private static AudioDecoderState? CreateAudioDecoder(uint codecType, AudioControl control)
+    {
+        if (codecType == AudiodecTypeAt9)
+        {
+            var atrac9 = new Atrac9DecodeState();
+            if (control.Atrac9Config is null || !atrac9.TryInitialize(control.Atrac9Config))
+            {
+                return null;
+            }
+
+            var config = atrac9.Config!;
+            return new AudioDecoderState
+            {
+                CodecType = codecType,
+                WordSize = control.WordSize,
+                Channels = config.ChannelCount,
+                SampleRate = config.SampleRate,
+                FrameBytes = config.SuperframeBytes,
+                FramesPerSuperframe = config.FramesPerSuperframe,
+                FrameSamples = config.FrameSamples,
+                Atrac9 = atrac9,
+            };
+        }
+
+        if (codecType == AudiodecTypeMp3)
+        {
+            return new AudioDecoderState
+            {
+                CodecType = codecType,
+                WordSize = control.WordSize,
+                Channels = 2,
+                SampleRate = 48_000,
+                FrameBytes = 1_441,
+                FramesPerSuperframe = 1,
+                FrameSamples = 1_152,
+            };
+        }
+
+        var channels = control.AacMaxChannels == 0
+            ? 2
+            : unchecked((int)Math.Min(control.AacMaxChannels, 8));
+        return new AudioDecoderState
+        {
+            CodecType = codecType,
+            WordSize = control.WordSize,
+            Channels = channels,
+            SampleRate = GetAacSampleRate(control.AacSampleRateIndex),
+            FrameBytes = 4_608,
+            FramesPerSuperframe = 1,
+            FrameSamples = 2_048,
+        };
+    }
+
+    private static void DecodeAtrac9(CpuContext ctx, AudioDecoderState decoder, AudioControl control)
+    {
+        var input = ArrayPool<byte>.Shared.Rent(checked((int)control.AuSize));
+        var output = ArrayPool<byte>.Shared.Rent(checked((int)control.PcmSize));
+        try
+        {
+            if (!ctx.Memory.TryRead(control.AuAddress, input.AsSpan(0, checked((int)control.AuSize))))
+            {
+                WriteAudioDecoderInfo(ctx, control.BsiInfoAddress, decoder, AudiodecErrorInvalidAuPointer);
+                WriteAudioBufferSizes(ctx, control, 0, 0);
+                return;
+            }
+
+            var result = decoder.Atrac9!.Decode(
+                input.AsSpan(0, checked((int)control.AuSize)),
+                output.AsSpan(0, checked((int)control.PcmSize)),
+                GetAtrac9Encoding(decoder.WordSize),
+                decoder.Channels,
+                multipleFrames: false);
+
+            var outputWritten = result.OutputWritten;
+            if (outputWritten != 0 &&
+                !ctx.Memory.TryWrite(control.PcmAddress, output.AsSpan(0, outputWritten)))
+            {
+                outputWritten = 0;
+            }
+
+            WriteAudioBufferSizes(
+                ctx,
+                control,
+                unchecked((uint)result.InputConsumed),
+                unchecked((uint)outputWritten));
+            WriteAudioDecoderInfo(ctx, control.BsiInfoAddress, decoder, result.Status);
+        }
+        finally
+        {
+            ArrayPool<byte>.Shared.Return(input);
+            ArrayPool<byte>.Shared.Return(output);
+        }
+    }
+
+    private static void DecodeAudioSilence(CpuContext ctx, AudioDecoderState decoder, AudioControl control)
+    {
+        var wantedPcm = checked(
+            decoder.FrameSamples *
+            decoder.Channels *
+            GetAudioBytesPerSample(decoder.WordSize));
+        var outputSize = Math.Min(control.PcmSize, unchecked((uint)wantedPcm));
+        ClearGuestMemory(ctx, control.PcmAddress, outputSize);
+        WriteAudioBufferSizes(
+            ctx,
+            control,
+            Math.Min(control.AuSize, unchecked((uint)decoder.FrameBytes)),
+            outputSize);
+        WriteAudioDecoderInfo(ctx, control.BsiInfoAddress, decoder, Ok);
+    }
+
+    private static void WriteAudioBufferSizes(
+        CpuContext ctx,
+        AudioControl control,
+        uint inputConsumed,
+        uint outputWritten)
+    {
+        Span<byte> value = stackalloc byte[sizeof(uint)];
+        BinaryPrimitives.WriteUInt32LittleEndian(value, inputConsumed);
+        _ = ctx.Memory.TryWrite(control.AuInfoAddress + 16, value);
+        BinaryPrimitives.WriteUInt32LittleEndian(value, outputWritten);
+        _ = ctx.Memory.TryWrite(control.PcmItemAddress + 16, value);
+    }
+
+    private static void WriteAudioDecoderInfo(
+        CpuContext ctx,
+        ulong infoAddress,
+        AudioDecoderState decoder,
+        int result)
+    {
+        if (decoder.CodecType == AudiodecTypeAt9)
+        {
+            Span<byte> info = stackalloc byte[36];
+            info.Clear();
+            BinaryPrimitives.WriteUInt32LittleEndian(info, unchecked((uint)info.Length));
+            BinaryPrimitives.WriteUInt32LittleEndian(info[4..], unchecked((uint)decoder.Channels));
+            var superframeSamples = checked(decoder.FrameSamples * decoder.FramesPerSuperframe);
+            var bitrate = superframeSamples == 0
+                ? 0u
+                : unchecked((uint)((ulong)decoder.FrameBytes * 8 * (uint)decoder.SampleRate /
+                                   (uint)superframeSamples));
+            BinaryPrimitives.WriteUInt32LittleEndian(info[8..], bitrate);
+            BinaryPrimitives.WriteUInt32LittleEndian(info[12..], unchecked((uint)decoder.SampleRate));
+            BinaryPrimitives.WriteUInt32LittleEndian(info[16..], unchecked((uint)decoder.FrameBytes));
+            BinaryPrimitives.WriteUInt32LittleEndian(info[20..], unchecked((uint)decoder.FramesPerSuperframe));
+            BinaryPrimitives.WriteUInt32LittleEndian(
+                info[24..],
+                unchecked((uint)(decoder.FrameBytes / Math.Max(decoder.FramesPerSuperframe, 1))));
+            BinaryPrimitives.WriteUInt32LittleEndian(info[28..], unchecked((uint)decoder.FrameSamples));
+            BinaryPrimitives.WriteInt32LittleEndian(info[32..], result);
+            _ = ctx.Memory.TryWrite(infoAddress, info);
+            return;
+        }
+
+        if (decoder.CodecType == AudiodecTypeMp3)
+        {
+            Span<byte> info = stackalloc byte[24];
+            info.Clear();
+            BinaryPrimitives.WriteUInt32LittleEndian(info, unchecked((uint)info.Length));
+            BinaryPrimitives.WriteInt32LittleEndian(info[20..], result);
+            _ = ctx.Memory.TryWrite(infoAddress, info);
+            return;
+        }
+
+        Span<byte> aacInfo = stackalloc byte[20];
+        aacInfo.Clear();
+        BinaryPrimitives.WriteUInt32LittleEndian(aacInfo, unchecked((uint)aacInfo.Length));
+        BinaryPrimitives.WriteUInt32LittleEndian(aacInfo[4..], unchecked((uint)decoder.SampleRate));
+        BinaryPrimitives.WriteUInt32LittleEndian(aacInfo[8..], unchecked((uint)decoder.Channels));
+        BinaryPrimitives.WriteInt32LittleEndian(aacInfo[16..], result);
+        _ = ctx.Memory.TryWrite(infoAddress, aacInfo);
+    }
+
+    private static Atrac9PcmEncoding GetAtrac9Encoding(int wordSize) =>
+        wordSize switch
+        {
+            0 => Atrac9PcmEncoding.Signed32,
+            1 => Atrac9PcmEncoding.Signed16,
+            2 => Atrac9PcmEncoding.Float,
+            _ => throw new ArgumentOutOfRangeException(nameof(wordSize)),
+        };
+
+    private static int GetAudioBytesPerSample(int wordSize) =>
+        wordSize == 1 ? sizeof(short) : sizeof(int);
+
+    private static int GetAacSampleRate(uint index)
+    {
+        ReadOnlySpan<int> rates =
+        [
+            96_000, 88_200, 64_000, 48_000, 44_100, 32_000,
+            24_000, 22_050, 16_000, 12_000, 11_025, 8_000,
+        ];
+        return index < rates.Length ? rates[unchecked((int)index)] : 48_000;
+    }
+
+    private static void ClearGuestMemory(CpuContext ctx, ulong address, uint byteCount)
+    {
+        Span<byte> zero = stackalloc byte[256];
+        var cursor = address;
+        var remaining = byteCount;
+        while (remaining != 0)
+        {
+            var length = unchecked((int)Math.Min(remaining, (uint)zero.Length));
+            if (!ctx.Memory.TryWrite(cursor, zero[..length]))
+            {
+                return;
+            }
+
+            cursor += unchecked((uint)length);
+            remaining -= unchecked((uint)length);
+        }
+    }
+
+    internal static void ResetAudioDecodersForTests()
+    {
+        AudioDecoders.Clear();
+        AudioCodecInitCounts.Clear();
+        Interlocked.Exchange(ref _nextAudioHandle, 0);
+    }
+
     private static bool TryWriteHandle(CpuContext ctx, ulong address, ulong handle) =>
         ctx.TryWriteUInt64(address, handle);
 

src/SharpEmu.Libs/Ngs2/Ngs2Exports.cs

@@ -30,7 +30,7 @@ public static class Ngs2Exports
     // The grain length defaults to 256 frames (matching the 8192-byte AudioOut
     // buffers games copy it into) until the title overrides it.
     private const int DefaultGrainSamples = 256;
-    private const double OutputSampleRate = 48000.0;
+    private const int DefaultSampleRate = 48000;
 
     private sealed class SystemState
     {
@@ -38,6 +38,7 @@ public static class Ngs2Exports
 
         public uint Uid { get; }
         public int GrainSamples { get; set; } = DefaultGrainSamples;
+        public int SampleRate { get; set; } = DefaultSampleRate;
     }
 
     private sealed record RackState(ulong SystemHandle, uint RackId);
@@ -496,6 +497,7 @@ public static class Ngs2Exports
             return SetReturn(ctx, (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
         }
 
+        Span<byte> renderBufferInfo = stackalloc byte[RenderBufferInfoSize];
         for (uint i = 0; i < bufferInfoCount; i++)
         {
             var entryAddress = bufferInfoAddress + (i * RenderBufferInfoSize);
@@ -527,10 +529,9 @@ public static class Ngs2Exports
 
                 if (ShouldTrace() && Interlocked.Increment(ref _renderInfoDumps) <= 4)
                 {
-                    Span<byte> rbi = stackalloc byte[RenderBufferInfoSize];
+                    ctx.Memory.TryRead(entryAddress, renderBufferInfo);
-                    ctx.Memory.TryRead(entryAddress, rbi);
                     Console.Error.WriteLine(
-                        $"[LOADER][TRACE] ngs2.renderbufinfo addr=0x{bufferAddress:X} size={bufferSize} ch={channels} raw={Convert.ToHexString(rbi)}");
+                        $"[LOADER][TRACE] ngs2.renderbufinfo addr=0x{bufferAddress:X} size={bufferSize} ch={channels} raw={Convert.ToHexString(renderBufferInfo)}");
                 }
             }
         }
@@ -552,6 +553,7 @@ public static class Ngs2Exports
         CpuContext ctx, ulong systemHandle, ulong bufferAddress, ulong bufferSize, int channels)
     {
         int grain;
+        int sampleRate;
         lock (StateGate)
         {
             if (!Systems.TryGetValue(systemHandle, out var system))
@@ -560,6 +562,7 @@ public static class Ngs2Exports
             }
 
             grain = system.GrainSamples;
+            sampleRate = system.SampleRate;
         }
 
         var capacityFrames = (int)Math.Min((ulong)grain, bufferSize / (ulong)(channels * sizeof(float)));
@@ -590,7 +593,7 @@ public static class Ngs2Exports
                         continue;
                     }
 
-                    MixOneVoice(accum, capacityFrames, channels, voice);
+                    MixOneVoice(accum, capacityFrames, channels, sampleRate, voice);
                     mixedAnything = true;
                 }
             }
@@ -606,15 +609,20 @@ public static class Ngs2Exports
         }
     }
 
-    // Resample one voice from its source rate to 48 kHz (nearest-sample) and add
+    // Resample one voice to the system rate and add
     // it to the front stereo pair. Advances the voice cursor and handles loop /
     // one-shot end. Must be called under StateGate.
-    private static void MixOneVoice(float[] accum, int frames, int channels, VoiceState voice)
+    private static void MixOneVoice(
+        float[] accum,
+        int frames,
+        int channels,
+        int outputSampleRate,
+        VoiceState voice)
     {
         var pcm = voice.Pcm!;
         var loopEnd = voice.LoopEnd > 0 && voice.LoopEnd <= pcm.Length ? voice.LoopEnd : pcm.Length;
         var loopStart = voice.LoopStart;
-        var step = voice.SourceRate / OutputSampleRate;
+        var step = voice.SourceRate / (double)outputSampleRate;
         var gain = voice.Gain / 32768f;
         var pos = voice.Position;
         for (var f = 0; f < frames; f++)
@@ -640,7 +648,14 @@ public static class Ngs2Exports
                 break;
             }
 
-            var sample = pcm[idx] * gain;
+            var next = idx + 1;
+            if (next >= loopEnd)
+            {
+                next = loopStart >= 0 && loopStart < loopEnd ? loopStart : idx;
+            }
+
+            var fraction = pos - idx;
+            var sample = (float)((pcm[idx] + ((pcm[next] - pcm[idx]) * fraction)) * gain);
             var baseIndex = f * channels;
             accum[baseIndex] += sample;
             if (channels > 1)
@@ -736,7 +751,27 @@ public static class Ngs2Exports
         ExportName = "sceNgs2SystemSetSampleRate",
         Target = Generation.Gen4 | Generation.Gen5,
         LibraryName = "libSceNgs2")]
-    public static int Ngs2SystemSetSampleRate(CpuContext ctx) => ValidateSystem(ctx);
+    public static int Ngs2SystemSetSampleRate(CpuContext ctx)
+    {
+        var systemHandle = ctx[CpuRegister.Rdi];
+        var sampleRate = unchecked((int)ctx[CpuRegister.Rsi]);
+        lock (StateGate)
+        {
+            if (!Systems.TryGetValue(systemHandle, out var system))
+            {
+                return SetReturn(ctx, OrbisNgs2ErrorInvalidSystemHandle);
+            }
+
+            if (sampleRate is < 8000 or > 192000)
+            {
+                return SetReturn(ctx, (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT);
+            }
+
+            system.SampleRate = sampleRate;
+        }
+
+        return SetReturn(ctx, 0);
+    }
 
     [SysAbiExport(
         Nid = "gThZqM5PYlQ",

tests/SharpEmu.Libs.Tests/Audio/AcmExportsTests.cs

@@ -0,0 +1,130 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using System.Buffers.Binary;
+using SharpEmu.HLE;
+using SharpEmu.Libs.Acm;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.Audio;
+
+[CollectionDefinition("AcmState", DisableParallelization = true)]
+public sealed class AcmStateCollection
+{
+    public const string Name = "AcmState";
+}
+
+[Collection(AcmStateCollection.Name)]
+public sealed class AcmExportsTests : IDisposable
+{
+    private const ulong MemoryBase = 0x1_1000_0000;
+    private const ulong ContextAddress = MemoryBase + 0x100;
+    private const ulong InfoArrayAddress = MemoryBase + 0x200;
+    private const ulong ErrorAddress = MemoryBase + 0x300;
+    private const ulong BatchAddress = MemoryBase + 0x400;
+
+    private readonly FakeCpuMemory _memory = new(MemoryBase, 0x1000);
+    private readonly CpuContext _ctx;
+
+    public AcmExportsTests()
+    {
+        AcmExports.ResetForTests();
+        _ctx = new CpuContext(_memory, Generation.Gen5);
+    }
+
+    [Fact]
+    public void ContextAndBatchLifecycle_UsesFourByteHandlesAndClearsErrors()
+    {
+        Span<byte> contextSentinel = stackalloc byte[8];
+        contextSentinel.Fill(0xCC);
+        Assert.True(_memory.TryWrite(ContextAddress, contextSentinel));
+
+        _ctx[CpuRegister.Rdi] = ContextAddress;
+        Assert.Equal(0, AcmExports.AcmContextCreate(_ctx));
+        var context = ReadUInt32(ContextAddress);
+        Assert.Equal(1u, context);
+        Assert.Equal(0xCCCCCCCCu, ReadUInt32(ContextAddress + 4));
+
+        Span<byte> errorSentinel = stackalloc byte[32];
+        errorSentinel.Fill(0xCC);
+        Assert.True(_memory.TryWrite(ErrorAddress, errorSentinel));
+        WriteUInt64(InfoArrayAddress, MemoryBase + 0x500);
+
+        _ctx[CpuRegister.Rdi] = context;
+        _ctx[CpuRegister.Rsi] = 1;
+        _ctx[CpuRegister.Rdx] = InfoArrayAddress;
+        _ctx[CpuRegister.Rcx] = ErrorAddress;
+        _ctx[CpuRegister.R8] = BatchAddress;
+        Assert.Equal(0, AcmExports.AcmBatchStartBuffers(_ctx));
+        Assert.Equal(1u, ReadUInt32(BatchAddress));
+        Assert.All(ReadBytes(ErrorAddress, 32), value => Assert.Equal(0, value));
+
+        _ctx[CpuRegister.Rdi] = context;
+        _ctx[CpuRegister.Rsi] = 1;
+        _ctx[CpuRegister.Rdx] = 0;
+        Assert.Equal(0, AcmExports.AcmBatchWait(_ctx));
+    }
+
+    [Fact]
+    public void BatchStartBuffers_RejectsUnknownContextAndMissingOutputs()
+    {
+        _ctx[CpuRegister.Rdi] = 99;
+        _ctx[CpuRegister.Rsi] = 1;
+        _ctx[CpuRegister.Rdx] = InfoArrayAddress;
+        _ctx[CpuRegister.R8] = BatchAddress;
+        Assert.Equal(
+            (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT,
+            AcmExports.AcmBatchStartBuffers(_ctx));
+
+        _ctx[CpuRegister.Rdi] = ContextAddress;
+        Assert.Equal(0, AcmExports.AcmContextCreate(_ctx));
+        _ctx[CpuRegister.Rdi] = ReadUInt32(ContextAddress);
+        _ctx[CpuRegister.Rsi] = 1;
+        _ctx[CpuRegister.Rdx] = 0;
+        _ctx[CpuRegister.R8] = BatchAddress;
+        Assert.Equal(
+            (int)OrbisGen2Result.ORBIS_GEN2_ERROR_INVALID_ARGUMENT,
+            AcmExports.AcmBatchStartBuffers(_ctx));
+    }
+
+    [Fact]
+    public void AcmBatchExports_RegisterForBothGenerations()
+    {
+        foreach (var generation in new[] { Generation.Gen4, Generation.Gen5 })
+        {
+            var manager = new ModuleManager();
+            manager.RegisterExports(SharpEmu.Generated.SysAbiExportRegistry.CreateExports(generation));
+
+            Assert.True(manager.TryGetExport("8fe55ktlNVo", out var start));
+            Assert.Equal("sceAcmBatchStartBuffers", start.Name);
+            Assert.True(manager.TryGetExport("RLN3gRlXJLE", out var wait));
+            Assert.Equal("sceAcmBatchWait", wait.Name);
+        }
+    }
+
+    public void Dispose()
+    {
+        AcmExports.ResetForTests();
+    }
+
+    private uint ReadUInt32(ulong address)
+    {
+        Span<byte> value = stackalloc byte[sizeof(uint)];
+        Assert.True(_memory.TryRead(address, value));
+        return BinaryPrimitives.ReadUInt32LittleEndian(value);
+    }
+
+    private byte[] ReadBytes(ulong address, int length)
+    {
+        var value = new byte[length];
+        Assert.True(_memory.TryRead(address, value));
+        return value;
+    }
+
+    private void WriteUInt64(ulong address, ulong value)
+    {
+        Span<byte> bytes = stackalloc byte[sizeof(ulong)];
+        BinaryPrimitives.WriteUInt64LittleEndian(bytes, value);
+        Assert.True(_memory.TryWrite(address, bytes));
+    }
+}

tests/SharpEmu.Libs.Tests/Audio/AjmExportsTests.cs

@@ -25,6 +25,9 @@ public sealed class AjmExportsTests : IDisposable
     private const ulong MemoryBase = 0x1_0000_0000;
     private const ulong ContextAddress = MemoryBase + 0x100;
     private const ulong InstanceAddress = MemoryBase + 0x200;
+    private const ulong BatchInfoAddress = MemoryBase + 0x300;
+    private const ulong StatisticsAddress = MemoryBase + 0x400;
+    private const ulong BatchBufferAddress = MemoryBase + 0x500;
 
     private readonly FakeCpuMemory _memory = new(MemoryBase, 0x1000);
     private readonly CpuContext _ctx;
@@ -80,6 +83,171 @@ public sealed class AjmExportsTests : IDisposable
         Assert.Equal(InvalidContext, RegisterCodec(contextId + 1, 1));
     }
 
+    [Fact]
+    public void MemoryRegistration_TracksValidContextAndToleratesRepeatedUnregister()
+    {
+        var contextId = Initialize();
+        const ulong address = 0x4_D4E0_0000;
+
+        Assert.Equal(0, RegisterMemory(contextId, address, 4));
+        Assert.Equal(0, UnregisterMemory(contextId, address));
+        Assert.Equal(0, UnregisterMemory(contextId, address));
+        Assert.Equal(InvalidContext, RegisterMemory(contextId + 1, address, 4));
+        Assert.Equal(InvalidContext, UnregisterMemory(contextId + 1, address));
+        Assert.Equal(InvalidParameter, RegisterMemory(contextId, 0, 4));
+        Assert.Equal(InvalidParameter, RegisterMemory(contextId, address, 0));
+        Assert.Equal(InvalidParameter, UnregisterMemory(contextId, 0));
+    }
+
+    [Fact]
+    public void BatchInitializeAndStatistics_WriteExpectedAbiStructures()
+    {
+        Span<byte> sentinel = stackalloc byte[48];
+        sentinel.Fill(0xCC);
+        Assert.True(_memory.TryWrite(StatisticsAddress, sentinel));
+
+        _ctx[CpuRegister.Rdi] = BatchBufferAddress;
+        _ctx[CpuRegister.Rsi] = 0x200;
+        _ctx[CpuRegister.Rdx] = BatchInfoAddress;
+        Assert.Equal(0, AjmExports.AjmBatchInitialize(_ctx));
+
+        Assert.Equal(BatchBufferAddress, ReadUInt64(BatchInfoAddress));
+        Assert.Equal(0ul, ReadUInt64(BatchInfoAddress + 8));
+        Assert.Equal(0x200ul, ReadUInt64(BatchInfoAddress + 16));
+        Assert.Equal(0ul, ReadUInt64(BatchInfoAddress + 24));
+        Assert.Equal(0ul, ReadUInt64(BatchInfoAddress + 32));
+
+        _ctx[CpuRegister.Rdi] = BatchInfoAddress;
+        _ctx[CpuRegister.Rsi] = StatisticsAddress;
+        _ctx.SetXmmRegister(0, BitConverter.SingleToUInt32Bits(0.25f), 0);
+        Assert.Equal(0, AjmExports.AjmBatchJobGetStatistics(_ctx));
+
+        Assert.Equal(88ul, ReadUInt64(BatchInfoAddress + 8));
+        Assert.Equal(BatchBufferAddress, ReadUInt64(BatchInfoAddress + 24));
+        Assert.Equal(0ul, ReadUInt64(BatchInfoAddress + 32));
+        Assert.All(ReadBytes(StatisticsAddress, 48), value => Assert.Equal(0, value));
+        Assert.All(ReadBytes(BatchBufferAddress, 88), value => Assert.Equal(0, value));
+    }
+
+    /// <summary>
+    /// Demon's Souls creates ATRAC9 voices with low flag words 1, 2, 4 and 8 —
+    /// the channel counts of the streams they carry. Rejecting any of them left
+    /// the title holding SCE_AJM_INSTANCE_INVALID for that voice, so its 4- and
+    /// 8-channel movie stems played silence.
+    /// </summary>
+    [Theory]
+    [InlineData(0x1_0000_0001ul)]
+    [InlineData(0x1_0000_0002ul)]
+    [InlineData(0x1_0000_0004ul)]
+    [InlineData(0x1_0000_0008ul)]
+    public void InstanceCreate_AcceptsEveryChannelCountFlagWord(ulong flags)
+    {
+        var contextId = Initialize();
+        Assert.Equal(0, RegisterCodec(contextId, 1));
+
+        Assert.Equal(0, CreateInstance(contextId, 1, flags, InstanceAddress));
+        Assert.Equal(0x4001u, ReadUInt32(InstanceAddress));
+    }
+
+    /// <summary>
+    /// sceAjmBatchJobRunSplit gathers arrays of AjmBuffer descriptors rather than
+    /// a single pointer/size pair, and its sideband layout is positional: result,
+    /// then only the blocks the job flags asked for.
+    /// </summary>
+    [Fact]
+    public void BatchJobRunSplit_GathersDescriptorsAndWritesFlaggedSideband()
+    {
+        const ulong inputDescriptors = MemoryBase + 0x600;
+        const ulong outputDescriptors = MemoryBase + 0x640;
+        const ulong inputData = MemoryBase + 0x700;
+        const ulong outputData = MemoryBase + 0x800;
+        const ulong sideband = MemoryBase + 0x900;
+        const ulong streamSideband = 1ul << 47;
+        const ulong multipleFrames = 1ul << 12;
+
+        var contextId = Initialize();
+        Assert.Equal(0, RegisterCodec(contextId, 2));
+        Assert.Equal(0, CreateInstance(contextId, 2, 0x2_0000_0002, InstanceAddress));
+        var instanceId = ReadUInt32(InstanceAddress);
+
+        InitializeBatch(BatchBufferAddress, 0x200, BatchInfoAddress);
+
+        // Two input descriptors totalling 0x30 bytes, one output of 0x40.
+        WriteUInt64(inputDescriptors, inputData);
+        WriteUInt64(inputDescriptors + 8, 0x20);
+        WriteUInt64(inputDescriptors + 16, inputData + 0x20);
+        WriteUInt64(inputDescriptors + 24, 0x10);
+        WriteUInt64(outputDescriptors, outputData);
+        WriteUInt64(outputDescriptors + 8, 0x40);
+
+        Span<byte> dirty = stackalloc byte[0x40];
+        dirty.Fill(0xAB);
+        Assert.True(_memory.TryWrite(outputData, dirty));
+
+        _ctx[CpuRegister.Rdi] = BatchInfoAddress;
+        _ctx[CpuRegister.Rsi] = instanceId;
+        _ctx[CpuRegister.Rdx] = streamSideband | multipleFrames;
+        _ctx[CpuRegister.Rcx] = inputDescriptors;
+        _ctx[CpuRegister.R8] = 2;
+        _ctx[CpuRegister.R9] = outputDescriptors;
+        WriteStackArgs(outputCount: 1, sidebandAddress: sideband, sidebandSize: 0x20);
+
+        Assert.Equal(0, AjmExports.AjmBatchJobRunSplit(_ctx));
+
+        // A non-ATRAC9 instance stays a silence stub: the output is cleared and
+        // the whole gathered input is reported consumed.
+        Assert.All(ReadBytes(outputData, 0x40), value => Assert.Equal(0, value));
+
+        var result = ReadBytes(sideband, 0x20);
+        Assert.Equal(0, BinaryPrimitives.ReadInt32LittleEndian(result));            // AjmSidebandResult
+        Assert.Equal(0x30, BinaryPrimitives.ReadInt32LittleEndian(result.AsSpan(8)));  // stream.input_consumed
+        Assert.Equal(0, BinaryPrimitives.ReadInt32LittleEndian(result.AsSpan(12)));    // stream.output_written
+        Assert.Equal(1u, BinaryPrimitives.ReadUInt32LittleEndian(result.AsSpan(24)));  // mframe.num_frames
+
+        // The batch cursor advanced past the job plus its descriptors.
+        Assert.True(ReadUInt64(BatchInfoAddress + 8) > 0);
+    }
+
+    [Fact]
+    public void BatchJobRunSplit_OmitsSidebandBlocksTheJobFlagsDidNotRequest()
+    {
+        const ulong inputDescriptors = MemoryBase + 0x600;
+        const ulong outputDescriptors = MemoryBase + 0x640;
+        const ulong inputData = MemoryBase + 0x700;
+        const ulong outputData = MemoryBase + 0x800;
+        const ulong sideband = MemoryBase + 0x900;
+
+        var contextId = Initialize();
+        Assert.Equal(0, RegisterCodec(contextId, 2));
+        Assert.Equal(0, CreateInstance(contextId, 2, 0x2_0000_0002, InstanceAddress));
+        var instanceId = ReadUInt32(InstanceAddress);
+
+        InitializeBatch(BatchBufferAddress, 0x200, BatchInfoAddress);
+        WriteUInt64(inputDescriptors, inputData);
+        WriteUInt64(inputDescriptors + 8, 0x20);
+        WriteUInt64(outputDescriptors, outputData);
+        WriteUInt64(outputDescriptors + 8, 0x40);
+
+        Span<byte> sentinel = stackalloc byte[0x20];
+        sentinel.Fill(0x5A);
+        Assert.True(_memory.TryWrite(sideband, sentinel));
+
+        _ctx[CpuRegister.Rdi] = BatchInfoAddress;
+        _ctx[CpuRegister.Rsi] = instanceId;
+        _ctx[CpuRegister.Rdx] = 0; // No stream sideband, no multiple-frames.
+        _ctx[CpuRegister.Rcx] = inputDescriptors;
+        _ctx[CpuRegister.R8] = 1;
+        _ctx[CpuRegister.R9] = outputDescriptors;
+        WriteStackArgs(outputCount: 1, sidebandAddress: sideband, sidebandSize: 0x20);
+
+        Assert.Equal(0, AjmExports.AjmBatchJobRunSplit(_ctx));
+
+        // Only the 8-byte result block is written; the rest keeps its sentinel.
+        var written = ReadBytes(sideband, 0x20);
+        Assert.Equal(0, BinaryPrimitives.ReadInt32LittleEndian(written));
+        Assert.All(written.AsSpan(8).ToArray(), value => Assert.Equal(0x5A, value));
+    }
+
     [Theory]
     [InlineData(23u)]
     [InlineData(24u)]
@@ -155,6 +323,12 @@ public sealed class AjmExportsTests : IDisposable
             Assert.Equal("sceAjmInstanceCreate", create.Name);
             Assert.True(manager.TryGetExport("RbLbuKv8zho", out var destroy));
             Assert.Equal("sceAjmInstanceDestroy", destroy.Name);
+            Assert.True(manager.TryGetExport("bkRHEYG6lEM", out var memoryRegister));
+            Assert.Equal("sceAjmMemoryRegister", memoryRegister.Name);
+            Assert.True(manager.TryGetExport("pIpGiaYkHkM", out var memoryUnregister));
+            Assert.Equal("sceAjmMemoryUnregister", memoryUnregister.Name);
+            Assert.True(manager.TryGetExport("3cAg7xN995U", out var statistics));
+            Assert.Equal("sceAjmBatchJobGetStatistics", statistics.Name);
         }
     }
 
@@ -179,6 +353,21 @@ public sealed class AjmExportsTests : IDisposable
         return AjmExports.AjmModuleRegister(_ctx);
     }
 
+    private int RegisterMemory(uint contextId, ulong address, ulong pages)
+    {
+        _ctx[CpuRegister.Rdi] = contextId;
+        _ctx[CpuRegister.Rsi] = address;
+        _ctx[CpuRegister.Rdx] = pages;
+        return AjmExports.AjmMemoryRegister(_ctx);
+    }
+
+    private int UnregisterMemory(uint contextId, ulong address)
+    {
+        _ctx[CpuRegister.Rdi] = contextId;
+        _ctx[CpuRegister.Rsi] = address;
+        return AjmExports.AjmMemoryUnregister(_ctx);
+    }
+
     private int CreateInstance(uint contextId, uint codecType, ulong flags, ulong outputAddress)
     {
         _ctx[CpuRegister.Rdi] = contextId;
@@ -202,6 +391,48 @@ public sealed class AjmExportsTests : IDisposable
         return BinaryPrimitives.ReadUInt32LittleEndian(value);
     }
 
+    private void InitializeBatch(ulong bufferAddress, ulong bufferSize, ulong infoAddress)
+    {
+        _ctx[CpuRegister.Rdi] = bufferAddress;
+        _ctx[CpuRegister.Rsi] = bufferSize;
+        _ctx[CpuRegister.Rdx] = infoAddress;
+        Assert.Equal(0, AjmExports.AjmBatchInitialize(_ctx));
+    }
+
+    /// <summary>
+    /// Places the seventh, eighth and ninth SysV arguments where the export reads
+    /// them: just past the return address slot at [rsp].
+    /// </summary>
+    private void WriteStackArgs(ulong outputCount, ulong sidebandAddress, ulong sidebandSize)
+    {
+        const ulong stackAddress = MemoryBase + 0xA00;
+        _ctx[CpuRegister.Rsp] = stackAddress;
+        WriteUInt64(stackAddress + 8, outputCount);
+        WriteUInt64(stackAddress + 16, sidebandAddress);
+        WriteUInt64(stackAddress + 24, sidebandSize);
+    }
+
+    private void WriteUInt64(ulong address, ulong value)
+    {
+        Span<byte> bytes = stackalloc byte[sizeof(ulong)];
+        BinaryPrimitives.WriteUInt64LittleEndian(bytes, value);
+        Assert.True(_memory.TryWrite(address, bytes));
+    }
+
+    private ulong ReadUInt64(ulong address)
+    {
+        Span<byte> value = stackalloc byte[sizeof(ulong)];
+        Assert.True(_memory.TryRead(address, value));
+        return BinaryPrimitives.ReadUInt64LittleEndian(value);
+    }
+
+    private byte[] ReadBytes(ulong address, int length)
+    {
+        var value = new byte[length];
+        Assert.True(_memory.TryRead(address, value));
+        return value;
+    }
+
     private void WriteUInt32(ulong address, uint value)
     {
         Span<byte> bytes = stackalloc byte[sizeof(uint)];