Support Dolby TrueHD in Fragmented MP4

[Hiroki-Tamaru]

Version

Media3 1.3.1

More version details

Tested with debug build. Also tested with version 1.3.0.

Devices that reproduce the issue

Fire TV Stick 4K - 2nd Generation (2023) - 8GB (Build Model: AFTKM)

Devices that do not reproduce the issue

No response

Reproducible in the demo app?

Yes

Reproduction steps

1. Use the ExoPlayer demo in this repository.
2. Play a Dolby TrueHD Fragmented MP4 file by adding it to media.exolist.json.
3. Observe the playback behavior.

Expected result

• The video player's time should progress normally.
• Playback should not stop.
• No "Audio sink error" should appear in the console.

Actual result

• The video player's time progresses very slowly and sometimes even decreases.
• For video files (not audio-only), the video also progresses very slowly.
• Playback stops after 55 seconds of real-time (corresponding to 4 seconds of displayed time).
• A large number of Audio sink errors appear in the console.

Audio sink error
androidx.media3.exoplayer.audio.AudioSink$UnexpectedDiscontinuityException: Unexpected audio track timestamp discontinuity: expected 1000000226666, got 1000000014166
at androidx.media3.exoplayer.audio.DefaultAudioSink.handleBuffer(DefaultAudioSink.java:994)
at androidx.media3.exoplayer.audio.MediaCodecAudioRenderer.processOutputBuffer(MediaCodecAudioRenderer.java:744)
at androidx.media3.exoplayer.mediacodec.MediaCodecRenderer.bypassRender(MediaCodecRenderer.java:2310)
at androidx.media3.exoplayer.mediacodec.MediaCodecRenderer.render(MediaCodecRenderer.java:822)
at androidx.media3.exoplayer.ExoPlayerImplInternal.doSomeWork(ExoPlayerImplInternal.java:1112)
at androidx.media3.exoplayer.ExoPlayerImplInternal.handleMessage(ExoPlayerImplInternal.java:544)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:223)
at android.os.HandlerThread.run(HandlerThread.java:67)

• The non-fragmented version of the same content can be played without any problem.

Media

Dolby TrueHD 48kHz audio-only fragmented mp4 (10sec fragment): https://d2pbyw961c6y8f.cloudfront.net/dolby_truehd/sunahara_5.1.4_48kHz_dthd_part1_fragmented.mp4 This is a Dolby TrueHD mp4 file created by dolby's official encoder (dolby enocoding engine) and fragmented using MP4Box tool.

Dolby TrueHD 48kHz audio-only mp4 : https://d2pbyw961c6y8f.cloudfront.net/dolby_truehd/sunahara_5.1.4_48kHz_dthd_part1.mp4 This is the non-fragmented version of the same content. This can be played without any problem.

Bug Report

• [X] You will email the zip file produced by adb bugreport to [email protected] after filing this issue.

[Hiroki-Tamaru]

When I investigated the source code (Mp4Extractor.java and FragmentedMp4Extractor.java), I found that Mp4Extractor uses TrueHdSampleRechunker, while FragmentedMp4Extractor does not. This might be the cause of this issue. Therefore, rather than being a bug, it may be more accurate to say that the combination of Fragmented MP4 files and TrueHD audio is not yet supported. Is there any plan to support this in the future?

[icbaker]

Thanks for pointing out this can likely be fixed by using TrueHdSampleRechunker in FragmentedMp4Extractor. I'm afraid we are unlikely to work on this soon, but we would consider a high quality PR implementing this.