Fix codec parsing for AVC streams

video-dev · Jan 4, 2024 · 959ce19 · 959ce19
1 parent 4cd3e5a
commit 959ce19
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/src/utils/mp4-tools.ts b/src/utils/mp4-tools.ts
@@ -310,8 +310,10 @@ function parseStsd(stsd: Uint8Array): { codec: string; encrypted: boolean } {
     case 'avc2':
     case 'avc3':
     case 'avc4':
-      // profile + compatibility + level
-      codec += '.' + toHex(stsd[111]) + toHex(stsd[112]) + toHex(stsd[113]);
+      // fourcCC starts at index 8, data takes 86 bytes until avcC box
+      // avcC box's header is 8 bytes and we ignore 'configurationVersion' (one byte)
+      // (total offset: 8 + 86 + 8 + 1 = 103): profile + compatibility + level
+      codec += '.' + toHex(stsd[103]) + toHex(stsd[104]) + toHex(stsd[105]);
       break;
     case 'mp4a': {
       const codecBox = findBox(sampleEntries, [fourCC])[0];