diff --git a/packages/frontend/apps/electron-renderer/src/app/effects/recording.ts b/packages/frontend/apps/electron-renderer/src/app/effects/recording.ts
index bbef4bbd2f..87434d699d 100644
--- a/packages/frontend/apps/electron-renderer/src/app/effects/recording.ts
+++ b/packages/frontend/apps/electron-renderer/src/app/effects/recording.ts
@@ -20,7 +20,7 @@ async function saveRecordingBlob(blobEngine: BlobEngine, filepath: string) {
     res.arrayBuffer()
   );
   const blob = new Blob([opusBuffer], {
-    type: 'audio/webm',
+    type: 'audio/mp4',
   });
   const blobId = await blobEngine.set(blob);
   logger.debug('Recording saved', blobId);
diff --git a/packages/frontend/apps/electron-renderer/src/popup/recording/index.tsx b/packages/frontend/apps/electron-renderer/src/popup/recording/index.tsx
index 0da59afe95..3930f6b6d9 100644
--- a/packages/frontend/apps/electron-renderer/src/popup/recording/index.tsx
+++ b/packages/frontend/apps/electron-renderer/src/popup/recording/index.tsx
@@ -5,7 +5,7 @@ import {
   createStreamEncoder,
   encodeRawBufferToOpus,
   type OpusStreamEncoder,
-} from '@affine/core/utils/webm-encoding';
+} from '@affine/core/utils/opus-encoding';
 import { apis, events } from '@affine/electron-api';
 import { useI18n } from '@affine/i18n';
 import track from '@affine/track';
diff --git a/packages/frontend/core/package.json b/packages/frontend/core/package.json
index 2b01f76df3..58a8944a61 100644
--- a/packages/frontend/core/package.json
+++ b/packages/frontend/core/package.json
@@ -66,6 +66,7 @@
     "lit": "^3.2.1",
     "lodash-es": "^4.17.21",
     "lottie-react": "^2.4.0",
+    "mp4-muxer": "^5.2.1",
     "nanoid": "^5.0.9",
     "next-themes": "^0.4.4",
     "query-string": "^9.1.1",
@@ -80,7 +81,6 @@
     "socket.io-client": "^4.8.1",
     "swr": "2.3.3",
     "tinykeys": "patch:tinykeys@npm%3A2.1.0#~/.yarn/patches/tinykeys-npm-2.1.0-819feeaed0.patch",
-    "webm-muxer": "^5.1.0",
     "y-protocols": "^1.0.6",
     "yjs": "^13.6.21",
     "zod": "^3.24.1"
diff --git a/packages/frontend/core/src/modules/media/entities/audio-attachment-block.ts b/packages/frontend/core/src/modules/media/entities/audio-attachment-block.ts
index 1040bb4123..5e4c8c972b 100644
--- a/packages/frontend/core/src/modules/media/entities/audio-attachment-block.ts
+++ b/packages/frontend/core/src/modules/media/entities/audio-attachment-block.ts
@@ -3,7 +3,7 @@ import {
   type TranscriptionBlockModel,
 } from '@affine/core/blocksuite/ai/blocks/transcription-block/model';
 import { insertFromMarkdown } from '@affine/core/blocksuite/utils';
-import { encodeAudioBlobToOpusSlices } from '@affine/core/utils/webm-encoding';
+import { encodeAudioBlobToOpusSlices } from '@affine/core/utils/opus-encoding';
 import { DebugLogger } from '@affine/debug';
 import { AiJobStatus } from '@affine/graphql';
 import track from '@affine/track';
diff --git a/packages/frontend/core/src/utils/webm-encoding.ts b/packages/frontend/core/src/utils/opus-encoding.ts
similarity index 94%
rename from packages/frontend/core/src/utils/webm-encoding.ts
rename to packages/frontend/core/src/utils/opus-encoding.ts
index cedc294ffb..27d8e11074 100644
--- a/packages/frontend/core/src/utils/webm-encoding.ts
+++ b/packages/frontend/core/src/utils/opus-encoding.ts
@@ -1,6 +1,6 @@
 import { DebugLogger } from '@affine/debug';
 import { apis } from '@affine/electron-api';
-import { ArrayBufferTarget, Muxer } from 'webm-muxer';
+import { ArrayBufferTarget, Muxer } from 'mp4-muxer';
 
 interface AudioEncodingConfig {
   sampleRate: number;
@@ -13,7 +13,7 @@ interface AudioEncodingResult {
   config: AudioEncodingConfig;
 }
 
-const logger = new DebugLogger('webm-encoding');
+const logger = new DebugLogger('opus-encoding');
 
 // Constants
 const DEFAULT_BITRATE = 64000;
@@ -134,9 +134,9 @@ async function encodeAudioFrames({
 }
 
 /**
- * Creates a WebM container with the encoded audio chunks
+ * Creates a mp4 container with the encoded audio chunks
  */
-export function muxToWebM(
+export function muxToMp4(
   encodedChunks: EncodedAudioChunk[],
   config: AudioEncodingConfig
 ): Uint8Array {
@@ -144,10 +144,11 @@ export function muxToWebM(
   const muxer = new Muxer({
     target,
     audio: {
-      codec: 'A_OPUS',
+      codec: 'opus',
       sampleRate: config.sampleRate,
       numberOfChannels: config.numberOfChannels,
     },
+    fastStart: 'in-memory',
   });
 
   for (const chunk of encodedChunks) {
@@ -185,7 +186,7 @@ async function encodeAudioBufferToOpus(
 }
 
 /**
- * Encodes raw audio data to Opus in WebM container.
+ * Encodes raw audio data to Opus in MP4 container.
  */
 export async function encodeRawBufferToOpus({
   filepath,
@@ -237,16 +238,16 @@ export async function encodeRawBufferToOpus({
     encoder,
   });
 
-  const webm = muxToWebM(encodedChunks, { sampleRate, numberOfChannels });
+  const mp4 = muxToMp4(encodedChunks, { sampleRate, numberOfChannels });
   logger.debug('Encoded raw buffer to Opus');
-  return webm;
+  return mp4;
 }
 
 /**
- * Encodes an audio file Blob to Opus in WebM container with specified bitrate.
+ * Encodes an audio file Blob to Opus in MP4 container with specified bitrate.
  * @param blob Input audio file blob (supports any browser-decodable format)
  * @param targetBitrate Target bitrate in bits per second (bps)
- * @returns Promise resolving to encoded WebM data as Uint8Array
+ * @returns Promise resolving to encoded MP4 data as Uint8Array
  */
 export async function encodeAudioBlobToOpus(
   blob: Blob | ArrayBuffer | Uint8Array,
@@ -263,9 +264,9 @@ export async function encodeAudioBlobToOpus(
       targetBitrate
     );
 
-    const webm = muxToWebM(encodedChunks, config);
+    const mp4 = muxToMp4(encodedChunks, config);
     logger.debug('Encoded audio blob to Opus');
-    return webm;
+    return mp4;
   } finally {
     await audioContext.close();
   }
@@ -371,14 +372,14 @@ export async function encodeAudioBlobToOpusSlices(
         encoder,
       });
 
-      // Mux to WebM and add to slices
-      const webm = muxToWebM(encodedChunks, {
+      // Mux to MP4 and add to slices
+      const mp4 = muxToMp4(encodedChunks, {
         sampleRate,
         numberOfChannels,
         bitrate: targetBitrate,
       });
 
-      slices.push(webm);
+      slices.push(mp4);
 
       // Move to next slice
       startSample = endSample;
@@ -471,7 +472,7 @@ export const createStreamEncoder = (
       logger.debug('Finishing encoding');
       await next();
       close();
-      const buffer = muxToWebM(encodedChunks, {
+      const buffer = muxToMp4(encodedChunks, {
         sampleRate: codecs.sampleRate,
         numberOfChannels: codecs.numberOfChannels,
         bitrate: codecs.targetBitrate,
diff --git a/yarn.lock b/yarn.lock
index 5037621b07..aee6dc5354 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -459,6 +459,7 @@ __metadata:
     lit: "npm:^3.2.1"
     lodash-es: "npm:^4.17.21"
     lottie-react: "npm:^2.4.0"
+    mp4-muxer: "npm:^5.2.1"
     nanoid: "npm:^5.0.9"
     next-themes: "npm:^0.4.4"
     query-string: "npm:^9.1.1"
@@ -474,7 +475,6 @@ __metadata:
     swr: "npm:2.3.3"
     tinykeys: "patch:tinykeys@npm%3A2.1.0#~/.yarn/patches/tinykeys-npm-2.1.0-819feeaed0.patch"
     vitest: "npm:3.1.3"
-    webm-muxer: "npm:^5.1.0"
     y-protocols: "npm:^1.0.6"
     yjs: "npm:^13.6.21"
     zod: "npm:^3.24.1"
@@ -14916,7 +14916,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/dom-webcodecs@npm:^0.1.4":
+"@types/dom-webcodecs@npm:^0.1.4, @types/dom-webcodecs@npm:^0.1.6":
   version: 0.1.15
   resolution: "@types/dom-webcodecs@npm:0.1.15"
   checksum: 10/0d1ce12007803b92594968c657e3bcdb24c5f4b7b89a3b094670bcc39f5c3b395adba1ab64a930007bd947ae6be1689ddd64ccc48127d1acf3ef7be63f3cdc98
@@ -26932,6 +26932,16 @@ __metadata:
   languageName: node
   linkType: hard
 
+"mp4-muxer@npm:^5.2.1":
+  version: 5.2.1
+  resolution: "mp4-muxer@npm:5.2.1"
+  dependencies:
+    "@types/dom-webcodecs": "npm:^0.1.6"
+    "@types/wicg-file-system-access": "npm:^2020.9.5"
+  checksum: 10/7169fd43e4a3a604c4590970276ff58bee479444530af8455ba66b70207e3317e74ae662b488df58f4619dd29973950228347585ec579539aa4356ead9d203be
+  languageName: node
+  linkType: hard
+
 "mri@npm:^1.2.0":
   version: 1.2.0
   resolution: "mri@npm:1.2.0"
@@ -34136,7 +34146,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"webm-muxer@npm:^5.0.3, webm-muxer@npm:^5.1.0":
+"webm-muxer@npm:^5.0.3":
   version: 5.1.2
   resolution: "webm-muxer@npm:5.1.2"
   dependencies: