Java mp4parser 片段序列不连续

Question

This use case is a service that manually encodes a series of uncompressed .wav media segments into .m4s fragments for broadcast via MPEG-DASH, using ffmpeg to compress the .wav to .aac and sannies/mp4parser to assemble the aac audio into a .m4s media fragment.

I created this public GitHub project to reproduce the issue in its entirety.

For example, here's the custom ChunkFragmentM4sBuilder.java class.

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This log is from ChunkFragmentM4sBuilderTest.java which results in the concatenated test output test-java-mp4parser.mp4 appears to be ok:

However, when I play the shipped playlist and segments using VLC, I see these failures in the logs:

mp4: Fragment sequence discontinuity detected 163497124 != 0

This error happens when VLC plays the following DASH playlist:

• test5.mpd
• test5-128k-163497124.m4s
• test5-128k-163497125.m4s
• test5-128k-163497126.m4s
• test5-128k-IS.mp4

And here is the latest implementation of my custom fragment builder class and additional notes:

Files.deleteIfExists(Path.of(m4sFilePath));
AACTrackImpl aacTrack=new AACTrackImpl(new FileDataSourceImpl(aacFilePath));
Movie movie=new Movie();
movie.addTrack(aacTrack);
Container mp4file=new ChunkFragmentM4sBuilder(seqNum).build(movie);
FileChannel fc=new FileOutputStream(m4sFilePath).getChannel();
mp4file.writeContainer(fc);
fc.close();

• ChunkFragmentM4sBuilderTest.log.txt
• test5-128k-IS.mp4
• test-java-mp4parser.mp4

Answer 1

The VLC message is just an info entry and not an error. It's expected since the starting sequence number corresponds to the live-edge.

You cannot playback that manifest once the live-edge went past the time of the last segment of those 3 provided. You would need to continue generating new segments corrresponding to the current time.

You can test this easily by making the manifest static, adding a segment list and modifiying the start number.

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Your segments look self-initialized but are not declared as such which will lead to problems. It also wastes bandwidth as you already provide an initialization segment.

As a reminder you should have:

• an init segment with ftyp and moov
• a series of media segments with styp (optional), moof , mdat