Le mar. 4 févr. 2025 à 06:15, Romain Beauxis <romain.beau...@gmail.com> a écrit : > > This is a series of 3 patches to allow proper decoding of ogg metadata > in chained ogg/flac streams. > > ogg/flac streams are pretty important because there are perhaps the only > combination of lossless audio codec and open-source container that > allows for proper transmittion of lossless audio data accross systems > such as Icecast, browser media tags and more. > > In the context of long-running audio streams, the ogg bitstream specs[1] > have historically been very badly implemented. For each new track and > each new metadata, the specs require the logical bitstream to come to a > full EOF and then start with a full new logical stream. > > These specs have often been confused with a gobal EOF by most > implementations. > > Furtunately, FFmpeg is a little better at that in that it is capable to > parsing chained logical ogg bitstreams and properly output either > encoded ogg packets or decoded audio. > > Chained bitstreams with more than one underlying type of content > (audio+video, etc) is not yet supported though this is a much less needed > feature. > > The purpose of these changes is to also allow proper decoding of > metadata associated with subsequent streams in chained ogg/flac > bitstream. > > This is done by simply intercepting ogg packets with comments in the > flac decoded, parsing the comment block and retaining it to be attached > with the next decoded audio frame. > > Along with the changes is a new FATE test validating the implementation. > > This solution keeps a proper separation of concerns: ogg packets are > sill output by the demuxer (as shown in the test) but consumer of decoded > data see decoded metadata in the decoded frames. > > Only drawback is that this adds a dependency on libavformat to > libavcodec. > > I have looked at moving the vorbis metadata parsing to libavutil but a > lot of definitions and utilities related to metadata are in fact located > in libavformat so perhaps this makes sense.
Of course, it was only after posting all this that I figured out how to properly do this. About to send an updated patch set sorry for the noise. -- Romain > Follow-up work not addressed in this series of patch: > * Ensure valid PTS in decoded frames of subsequent streams? > * Generalize this approach to other chained ogg codec. > > Thanks, > -- Romain > > Romain Beauxis (3): > libavformat/oggdec: Allow first parameter in ff_vorbis_comment to be a > generic AVClass struct > libavcodec/flacdec: parse vorbis metadata from ogg packets, add them > to the next decoded frame. > Add stream dump test with test for ogg/flac. > > libavcodec/flacdec.c | 12 +- > libavformat/oggdec.h | 5 +- > libavformat/oggparsevorbis.c | 4 +- > tests/Makefile | 2 + > tests/api/Makefile | 2 +- > tests/api/api-dump-stream-meta-test.c | 169 ++++++++++++++++++++++++++ > tests/fate/api.mak | 5 + > tests/fate/ogg-flac.mak | 11 ++ > 8 files changed, 205 insertions(+), 5 deletions(-) > create mode 100644 tests/api/api-dump-stream-meta-test.c > create mode 100644 tests/fate/ogg-flac.mak > > -- > 2.39.5 (Apple Git-154) > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
