Re: [FFmpeg-devel] [PATCH v3 1/2] libavformat/oggdec.c: Changing the packet() callback API/Return value

[Romain Beauxis <romain.beauxis@gmail.com>]

Le dim. 4 mai 2025 à 09:04, Michael Niedermayer <michael@niedermayer.cc> a
écrit :
>
> On Sat, May 03, 2025 at 12:03:28PM -0500, Romain Beauxis wrote:
> > ---
> >  libavformat/oggdec.c | 22 ++++++++++++++--------
> >  libavformat/oggdec.h |  6 ++++++
> >  2 files changed, 20 insertions(+), 8 deletions(-)
> >
> > diff --git a/libavformat/oggdec.c b/libavformat/oggdec.c
> > index 5339fdd32c..9baf8040a9 100644
> > --- a/libavformat/oggdec.c
> > +++ b/libavformat/oggdec.c
> > @@ -605,20 +605,26 @@ static int ogg_packet(AVFormatContext *s, int
*sid, int *dstart, int *dsize,
> >      } else {
> >          os->pflags    = 0;
> >          os->pduration = 0;
> > +
> > +        ret = 0;
> >          if (os->codec && os->codec->packet) {
> >              if ((ret = os->codec->packet(s, idx)) < 0) {
> >                  av_log(s, AV_LOG_ERROR, "Packet processing failed:
%s\n", av_err2str(ret));
> >                  return ret;
> >              }
> >          }
> > -        if (sid)
> > -            *sid = idx;
> > -        if (dstart)
> > -            *dstart = os->pstart;
> > -        if (dsize)
> > -            *dsize = os->psize;
> > -        if (fpos)
> > -            *fpos = os->sync_pos;
> > +
> > +        if (!ret) {
> > +            if (sid)
> > +                *sid = idx;
> > +            if (dstart)
> > +                *dstart = os->pstart;
> > +            if (dsize)
> > +                *dsize = os->psize;
> > +            if (fpos)
> > +                *fpos = os->sync_pos;
> > +        }
> > +
> >          os->pstart  += os->psize;
> >          os->psize    = 0;
> >          if(os->pstart == os->bufpos)
> > diff --git a/libavformat/oggdec.h b/libavformat/oggdec.h
> > index 43df23f4cb..09f698f99a 100644
> > --- a/libavformat/oggdec.h
> > +++ b/libavformat/oggdec.h
> > @@ -38,6 +38,12 @@ struct ogg_codec {
> >       *         -1 if an error occurred or for unsupported stream
> >       */
> >      int (*header)(AVFormatContext *, int);
> > +    /**
> > +     * Attempt to process a packet as a data packet
> > +     * @return 1 if the packet was a header from a chained bitstream.
> > +     *         0 if the packet was a regular data packet.
> > +     *         -1 if an error occurred or for unsupported stream
> > +     */
> >      int (*packet)(AVFormatContext *, int);
> >      /**
> >       * Translate a granule into a timestamp.
>
> Iam still confused by this
>
> If this changes the API for ogg_codec.packet()
> and in the same patch theres a change to ogg_packet() which uses
> ogg_codec.packet()
>
> but then there is a 2nd patch that actually changes the implementations
> of ogg_codec.packet() :
>
> so after the first patch, the API documentation is not correct,
> I thought that documentation and implementation change would happen
> in the same patch and the use of the more refined API would then be in
> a 2nd patch
> am i missing something here ?

I must have misinterpreted your previous message:

> Do you think this would merit a seperate patch ?
> I mean patch #1 changing the packet() return value and clearly stating
> that in the commit message
> and patch #2 using the new value ?

Looks like you meant to do the reverse of what I sent, let me make it more
clear:

Order #1:
1. Change the ogg_codec.packet() implementations to return 1 when skipping
should occur
2. Consume that value in ogg_packet and implement the actual skip in the
ogg bitstream

Order #2:
1. Introduce a new API functionality in ogg_packet that is opt-in, i.e.
returning 1 in the ogg packet function to optionally skip a packet from the
ogg bitstream. API is available but not used yet.
2. Implement the functionality in all the different ogg_codec.packet()
codec-specific files to skip header packets.

Order #2 is what I sent. To me it makes more sense. One of the reasons for
this order is that, also, the test diff would be colocated with the change
in the atual codec-specific code. If you do order #1, the test diff would
occur in the generic changes to ogg_packet, making it harder to track where
the code that actually implements the test output changes comes from.

At the end of the day, I'm happy to commit these changes in any shape or
form so we can move forward with the rest of this work.

Thanks,
-- Romain

> --- a/libavformat/oggparseopus.c
> +++ b/libavformat/oggparseopus.c
> @@ -125,6 +125,17 @@ static int opus_packet(AVFormatContext *avf, int idx)
>          return AVERROR_INVALIDDATA;
>      }
>
> +     if (os->psize > 8 && !memcmp(packet, "OpusHead", 8)) {
> +        if ((ret = ff_alloc_extradata(st->codecpar, os->psize)) < 0)
> +            return ret;
> +
> +        memcpy(st->codecpar->extradata, packet, os->psize);
> +        return 1;
> +    }
> +
> +    if (os->psize > 8 && !memcmp(packet, "OpusTags", 8))
> +        return 1;
> +
>      if ((!os->lastpts || os->lastpts == AV_NOPTS_VALUE) && !(os->flags &
OGG_FLAG_EOS)) {
>          int seg, d;
>          int duration;
>
>
> const struct ogg_codec ff_opus_codec = {
>     .name             = "Opus",
>     .magic            = "OpusHead",
>     .magicsize        = 8,
>     .header           = opus_header,
>     .packet           = opus_packet,
>     .nb_header        = 1,
>
>
>
> diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
> index 9f50ab9ffc..8b4ae872d2 100644
> --- a/libavformat/oggparsevorbis.c
> +++ b/libavformat/oggparsevorbis.c
> @@ -418,6 +418,7 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>      struct ogg_stream *os = ogg->streams + idx;
>      struct oggvorbis_private *priv = os->private;
>      int duration, flags = 0;
> +    int skip_packet = 0;
>
>      if (!priv->vp)
>          return AVERROR_INVALIDDATA;
> @@ -480,7 +481,13 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>          if (duration < 0) {
>              os->pflags |= AV_PKT_FLAG_CORRUPT;
>              return 0;
> -        } else if (flags & VORBIS_FLAG_COMMENT) {
> +        }
> +
> +        if (flags &
> +            (VORBIS_FLAG_HEADER | VORBIS_FLAG_COMMENT |
VORBIS_FLAG_SETUP))
> +            skip_packet = 1;
> +
> +        if (flags & VORBIS_FLAG_COMMENT) {
>              vorbis_update_metadata(s, idx);
>              flags = 0;
>          }
> @@ -505,7 +512,7 @@ static int vorbis_packet(AVFormatContext *s, int idx)
>          priv->final_duration += os->pduration;
>      }
>
> -    return 0;
> +    return skip_packet;
>  }
>
>
>
>
>
>
>
> > --
> > 2.39.5 (Apple Git-154)
> >
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> >
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> >
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> I have often repented speaking, but never of holding my tongue.
> -- Xenocrates
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