[FFmpeg-devel] [PATCH] Parse ogg/flac header again after processing a new chained ogg bitstream.

[Romain Beauxis]

Hi all!

Le sam. 18 janv. 2025 à 11:54, Romain Beauxis
<romain.beauxis at gmail.com> a écrit :
>
> This patch makes sure that ogg/flac headers are parsed again when
> encountering a new logic stream inside a chained ogg bistream[1].
>
> This patches makes it possible to retrieve metadata in chained ogg/flac
> bitstreams. It is particularly important because ogg/flac is one of the
> only (if not the only one) lossless container supported over HTTP/icecast.
>
> The patch has been tested with various ogg/flac encoders and appears to
> work fine with ffmpeg.

Anybody interested in reviewing/testing the patch? Happy to provide
some streams or you can literally concatenate two ogg/flac files
together.

I know for a fact that it would be very useful to people using ffmpeg
either directly or through its libraries.

Thanks,
-- Romain

> 1: https://xiph.org/ogg/doc/oggstream.html
>
> ---
>  libavformat/oggdec.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/oggdec.c b/libavformat/oggdec.c
> index 5339fdd32c..d986e19817 100644
> --- a/libavformat/oggdec.c
> +++ b/libavformat/oggdec.c
> @@ -239,8 +239,11 @@ static int ogg_replace_stream(AVFormatContext *s, uint32_t serial, char *magic,
>      os->start_trimming = 0;
>      os->end_trimming = 0;
>
> -    /* Chained files have extradata as a new packet */
> -    if (codec == &ff_opus_codec)
> +    /* Parse opus and flac header on new chained bitstreams.
> +     * For opus, header contains required extradata as new packet.
> +     * For both formats, this makes it possible to read chained metadata. */
> +    if (codec == &ff_opus_codec ||
> +        codec == &ff_flac_codec)
>          os->header = -1;
>
>      return i;
> --
> 2.39.5 (Apple Git-154)
>