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Eliminate zero-sized samples from contributing to the audio track.

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Eliminating unnecessary and potentially counter-productive zero-sized
samples from the audio trak. The Android MP4 multiplexer tends to add
them at the very end of the audio stream. Their presence may negatively
affect the declared audio stream duration, and pose further complications
down the road.

The changes are verified on Samsung A54 (Android 14) device.
This commit is contained in:
Milan Stevanovic
2025-03-19 09:29:04 -07:00
committed by Cody Henthorne
parent c1f96e5bd3
commit f0e6b2944a
1 changed files with 27 additions and 1 deletions
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28
video/lib/src/main/java/org/thoughtcrime/securesms/video/videoconverter/muxer/Mp4Writer.java
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@@ -277,7 +277,33 @@ final class Mp4Writer extends DefaultBoxes implements SampleSink {
final @NonNull StreamingSample streamingSample,
final @NonNull StreamingTrack streamingTrack) throws IOException
{
if (streamingSample.getContent().limit() == 0) {
//
// For currently unknown reason, the STSZ table of AAC audio stream
// related to the very last chunk comes with the extra table elements
// whose value is zero.
//
// The ISO MP4 spec does not absolutely prohibit such a case, but strongly
// stipulates that the stream has to have the inner logic to support
// the zero length audio frames (QCELP happens to be one such example).
//
// Spec excerpt:
// ----------------------------------------------------------------------
// 8.7.3 Sample Size Boxes
// 8.7.3.1 Definition
// ...
// NOTE A sample size of zero is not prohibited in general, but it
// must be valid and defined for the coding system, as defined by
// the sample entry, that the sample belongs to
// ----------------------------------------------------------------------
//
// In all other cases, having zero STSZ table values is very illogical
// and may pose the problems down the road. Here we will eliminate such
// samples from all the related bookkeeping
//
Log.d(TAG, "skipping zero-sized sample");
return;
}
TrackBox tb = trackBoxes.get(streamingTrack);
if (tb == null) {
tb = new TrackBox();