Le lun. 11 août 2025 à 19:21, Romain Beauxis <romain.beau...@gmail.com> a écrit : > > Le lun. 11 août 2025 à 17:31, Yalda <mart...@proxyid.net> a écrit : > > > > Hi Romain, > > Hi! > > > I can try to help out here. > > I am not familiar with the OGG spec but I can at least help with > > reviews/facilitate to a degree, and it's free so I can read if needed. > > > > It seems you are trying to fix issues in and improve OGG support. > > Can you give me a brief summary of your goals? > > (i.e. what should I look at first to assist?) > > Great, thank you so much for taking the time. > > Got the current work, I would like to improve ffmpeg support for ogg > stream chaining. > > # Ogg chaining > > The documentation for this feature is here: > https://xiph.org/ogg/doc/oggstream.html > > Ogg stream chaining is used in particular to send a sequence of > tracks. Each time a track ends, the current bitstream is terminated > and a new one created. This is also required to pass in-band metadata. > > In practice, ogg chaining works pretty much like concatenating ogg files. > > Historically, this spec has proven to be a pretty bad design. There > are very few tools handling this properly. Most of them treat the end > of the first logical bitstream as an end of file. > > However, and furthermore unfortunately, ogg is still pretty popular > for audio streaming, especially using icecast. In particular it is the > only container that currently supports lossless codec (flac) with > in-band metadata. > > # In ffmpeg > > In ffmpeg, support for chained streams is essentially missing. In the > following, I'm talking about the state of the code before I started > working on it. > > 1- Most decoders are able to keep decoding after the first logical > bitstreams. However, in most cases, secondary and later metadata are > lost. > > 2- The demuxer outputs ogg header packets as ffmpeg packets from > secondary and further streams. These packets should be suppressed by > the demuxer and instead passed as extradata. > > 3- PTS and later DTS of secondary and further streams are > discontinuous: they restart from their initial value.
I meant the other way :-) DTS and then PTS > 4- It is currently not possible to do a ffmpeg -c copy copy of > sequentialize ogg streams. > > I'm trying to fix those 4 points. > > The work that I have been doing has been focused on the most popular > codecs, namely opus, flac and vorbis. I'm happy to extend to more but, > at this point, I'd consider all the other one as deprecated > personally. > > Issue #1 is partially addressed with some patches current in the code > base and some patches pending. > > But, first, I'd like to focus on issue #2 because it is almost complete. > > Currently, issue #2 has been addressed by a series of patches reviewed > and merged by Michael and Lynne. > > 2431fd0b275: introduce a dump utility to track and check changes to > the bitstreams on each patch > 6d54af6599 and a9d39d6eb9: change the meaning of ogg_codec->packet > return value of 1 to make it possible to direct the demuxer to skip > some decoded packets > > At this point, the stage is ready to start skipping ogg header packets: > 2fb6416dd0: skip ogg header packets in ogg/flac streams > 9c5ed57f94: skip ogg header packets in ogg/opus streams > 574f634e49: skip ogg header packets in ogg/vorbis streams > > The last one was clearly erroneous and reverted by Andreas Rheinhardt > > The PR here: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20026 is the > fixed version, following Andreas Rheinhardt feedback. > > The fixed patch packs all 3 vorbis header into a bytestream structure, > passes it as extra data and uses it on the decoder side. > > Following Michael's review, support for demuxed ogg headers is kept as > legacy in case libavcodec is linked with an older version of > libavformat. > > A new decoding routine is added to handle the new extradata-based > header packets. > > Let me know if that is enough information for you to help and thanks again! > -- Romain _______________________________________________ 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".
