Bug 1566389 - Store the parsed encoder delay and padding when demuxing an mp3 file. r=jya,bryce

Differential Revision: https://phabricator.services.mozilla.com/D91770

dom/media/mp3/MP3Demuxer.cpp

@@ -626,8 +626,17 @@ already_AddRefed<MediaRawData> MP3TrackDemuxer::GetNextFrame(
   if (mNumParsedFrames == 1) {
     // First frame parsed, let's read VBR info if available.
     BufferReader reader(frame->Data(), frame->Size());
-    mParser.ParseVBRHeader(&reader);
     mFirstFrameOffset = frame->mOffset;
+
+    if (mParser.ParseVBRHeader(&reader)) {
+      // Parsing was successful
+      if (mParser.VBRInfo().Type() == FrameParser::VBRHeader::XING) {
+        MP3LOGV("XING header present, skipping encoder delay (%u frames)",
+                mParser.VBRInfo().EncoderDelay());
+        mEncoderDelay = mParser.VBRInfo().EncoderDelay();
+        mEncoderPadding = mParser.VBRInfo().EncoderPadding();
+      }
+    }
   }
 
   MP3LOGV("GetNext() End mOffset=%" PRIu64 " mNumParsedFrames=%" PRIu64

dom/media/mp3/MP3Demuxer.h

@@ -162,6 +162,11 @@ class MP3TrackDemuxer : public MediaTrackDemuxer,
 
   // Audio track config info.
   UniquePtr<AudioInfo> mInfo;
+
+  // Number of frames to skip at the beginning
+  uint32_t mEncoderDelay = 0;
+  // Number of frames to skip at the end
+  uint32_t mEncoderPadding = 0;
 };
 
 }  // namespace mozilla