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Add support for seek preroll in AAC and other audio codecs 

Closes #452.

Change-Id: I0f648c4fa6c861540b050a5b4e9878987c8383e5
This commit is contained in:
KongQun Yang 2018-08-21 15:52:09 -07:00
parent f49b89280c
commit e5b8b3ec64
4 changed files with 16 additions and 24 deletions
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packager/app/test/testdata/opus-vp9-mp4-with-encryption/bear-320x240-vp9-opus-audio.mp4 vendored
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packager/app/test/testdata/opus-vp9-mp4-with-encryption/decrypted-bear-320x240-vp9-opus-audio-0.mp4 vendored
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packager/app/test/testdata/opus-vp9-mp4-with-encryption/output.mpd vendored
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@ -10,8 +10,8 @@
<Representation id="0" bandwidth="86874" codecs="opus" mimeType="audio/mp4" audioSamplingRate="48000">
<AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"/>
<BaseURL>bear-320x240-vp9-opus-audio.mp4</BaseURL>
<SegmentBase indexRange="975-1042" timescale="1000000" presentationTimeOffset="37000">
<Initialization range="0-974"/>
<SegmentBase indexRange="947-1014" timescale="1000000" presentationTimeOffset="37000">
<Initialization range="0-946"/>
</SegmentBase>
</Representation>
</AdaptationSet>

36
packager/media/formats/mp4/mp4_muxer.cc
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@ -135,6 +135,16 @@ void GenerateSinf(FourCC old_type,
track_encryption.default_kid = encryption_config.key_id;
}
// The roll distance is expressed in sample units and always takes negative
// values.
int16_t GetRollDistance(uint64_t seek_preroll_ns, uint32_t sampling_frequency) {
const double kNanosecondsPerSecond = 1000000000;
const double preroll_in_samples =
seek_preroll_ns / kNanosecondsPerSecond * sampling_frequency;
// Round to closest integer.
return -static_cast<int16_t>(preroll_in_samples + 0.5);
}
} // namespace
MP4Muxer::MP4Muxer(const MuxerOptions& options) : Muxer(options) {}
@ -497,34 +507,16 @@ bool MP4Muxer::GenerateAudioTrak(const AudioStreamInfo* audio_info,
entry.format = FOURCC_enca;
}
// Opus requires at least one sample group description box and at least one
// sample to group box with grouping type 'roll' within sample table box.
if (audio_info->codec() == kCodecOpus) {
if (audio_info->seek_preroll_ns() > 0) {
sample_table.sample_group_descriptions.resize(1);
SampleGroupDescription& sample_group_description =
sample_table.sample_group_descriptions.back();
sample_group_description.grouping_type = FOURCC_roll;
sample_group_description.audio_roll_recovery_entries.resize(1);
// The roll distance is expressed in sample units and always takes negative
// values.
const uint64_t kNanosecondsPerSecond = 1000000000ull;
sample_group_description.audio_roll_recovery_entries[0].roll_distance =
(0 - (audio_info->seek_preroll_ns() * audio.samplerate +
kNanosecondsPerSecond / 2)) /
kNanosecondsPerSecond;
sample_table.sample_to_groups.resize(1);
SampleToGroup& sample_to_group = sample_table.sample_to_groups.back();
sample_to_group.grouping_type = FOURCC_roll;
sample_to_group.entries.resize(1);
SampleToGroupEntry& sample_to_group_entry = sample_to_group.entries.back();
// All samples are in track fragments.
sample_to_group_entry.sample_count = 0;
sample_to_group_entry.group_description_index =
SampleToGroupEntry::kTrackGroupDescriptionIndexBase + 1;
} else if (audio_info->seek_preroll_ns() != 0) {
LOG(WARNING) << "Unexpected seek preroll for codec " << audio_info->codec();
GetRollDistance(audio_info->seek_preroll_ns(), audio.samplerate);
// sample to group box is not allowed in the init segment per CMAF
// specification. It is put in the fragment instead.
}
return true;
}