fix(utils/detect-mimetype): add support for detecting id3 tags (#5737)

.changeset/gentle-toys-smile.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+fix(utils/detect-mimetype): add support for detecting id3 tags

packages/ai/core/util/detect-media-type.test.ts

@@ -4,6 +4,7 @@ import {
   detectMediaType,
   imageMediaTypeSignatures,
 } from './detect-media-type';
+import { convertUint8ArrayToBase64 } from '@ai-sdk/provider-utils';
 
 describe('detectMediaType', () => {
   describe('GIF', () => {
@@ -228,6 +229,80 @@ describe('detectMediaType', () => {
         }),
       ).toBe('audio/mpeg');
     });
+
+    it('should detect MP3 with ID3v2 tags from bytes', () => {
+      const mp3WithID3Bytes = new Uint8Array([
+        0x49,
+        0x44,
+        0x33, // 'ID3'
+        0x03,
+        0x00, // version
+        0x00, // flags
+        0x00,
+        0x00,
+        0x00,
+        0x0a, // size (10 bytes)
+        // 10 bytes of ID3 data
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        // MP3 frame header
+        0xff,
+        0xfb,
+        0x00,
+        0x00,
+      ]);
+      expect(
+        detectMediaType({
+          data: mp3WithID3Bytes,
+          signatures: audioMediaTypeSignatures,
+        }),
+      ).toBe('audio/mpeg');
+    });
+    it('should detect MP3 with ID3v2 tags from base64', () => {
+      const mp3WithID3Bytes = new Uint8Array([
+        0x49,
+        0x44,
+        0x33, // 'ID3'
+        0x03,
+        0x00, // version
+        0x00, // flags
+        0x00,
+        0x00,
+        0x00,
+        0x0a, // size (10 bytes)
+        // 10 bytes of ID3 data
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        0x00,
+        // MP3 frame header
+        0xff,
+        0xfb,
+        0x00,
+        0x00,
+      ]);
+      const mp3WithID3Base64 = convertUint8ArrayToBase64(mp3WithID3Bytes);
+      expect(
+        detectMediaType({
+          data: mp3WithID3Base64,
+          signatures: audioMediaTypeSignatures,
+        }),
+      ).toBe('audio/mpeg');
+    });
   });
 
   describe('WAV', () => {

packages/ai/core/util/detect-media-type.ts

@@ -1,3 +1,5 @@
+import { convertBase64ToUint8Array } from '@ai-sdk/provider-utils';
+
 export const imageMediaTypeSignatures = [
   {
     mediaType: 'image/gif' as const,
@@ -83,6 +85,31 @@ export const audioMediaTypeSignatures = [
   },
 ] as const;
 
+const stripID3 = (data: Uint8Array | string) => {
+  const bytes =
+    typeof data === 'string' ? convertBase64ToUint8Array(data) : data;
+  const id3Size =
+    ((bytes[6] & 0x7f) << 21) |
+    ((bytes[7] & 0x7f) << 14) |
+    ((bytes[8] & 0x7f) << 7) |
+    (bytes[9] & 0x7f);
+
+  // The raw MP3 starts here
+  return bytes.slice(id3Size + 10);
+};
+
+function stripID3TagsIfPresent(data: Uint8Array | string): Uint8Array | string {
+  const hasId3 =
+    (typeof data === 'string' && data.startsWith('SUQz')) ||
+    (typeof data !== 'string' &&
+      data.length > 10 &&
+      data[0] === 0x49 && // 'I'
+      data[1] === 0x44 && // 'D'
+      data[2] === 0x33); // '3'
+
+  return hasId3 ? stripID3(data) : data;
+}
+
 /**
  * Detect the media IANA media type of a file using a list of signatures.
  *
@@ -97,12 +124,16 @@ export function detectMediaType({
   data: Uint8Array | string;
   signatures: typeof audioMediaTypeSignatures | typeof imageMediaTypeSignatures;
 }): (typeof signatures)[number]['mediaType'] | undefined {
+  const processedData = stripID3TagsIfPresent(data);
+
   for (const signature of signatures) {
     if (
-      typeof data === 'string'
-        ? data.startsWith(signature.base64Prefix)
-        : data.length >= signature.bytesPrefix.length &&
-          signature.bytesPrefix.every((byte, index) => data[index] === byte)
+      typeof processedData === 'string'
+        ? processedData.startsWith(signature.base64Prefix)
+        : processedData.length >= signature.bytesPrefix.length &&
+          signature.bytesPrefix.every(
+            (byte, index) => processedData[index] === byte,
+          )
     ) {
       return signature.mediaType;
     }