Re: [FFmpeg-devel] [PATCH v3 1/2] avformat: refactor ff_stream_encode_params_copy() to ff_stream_params_copy()

[Pierre-Anthony Lemieux <pal@sandflow.com>]

On Tue, Jul 26, 2022 at 8:17 AM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> pal@sandflow.com:
> > From: Pierre-Anthony Lemieux <pal@palemieux.com>
> >
> > As discussed at https://ffmpeg.org/pipermail/ffmpeg-devel/2022-July/298491.html.
> > Note that ff_stream_params_copy() does not copy the index field, which is
> > usually set by avformat_new_stream().
> >
> > ---
> >  libavformat/avformat.c   | 37 +++++++++++++++++++++++++++++++++++++
> >  libavformat/fifo.c       |  2 +-
> >  libavformat/internal.h   | 10 ++++++++++
> >  libavformat/mux.h        |  9 ---------
> >  libavformat/mux_utils.c  | 28 ----------------------------
> >  libavformat/segment.c    |  2 +-
> >  libavformat/tee.c        |  2 +-
> >  libavformat/webm_chunk.c |  2 +-
> >  8 files changed, 51 insertions(+), 41 deletions(-)
> >
> > diff --git a/libavformat/avformat.c b/libavformat/avformat.c
> > index 30d6ea6a49..c426dbfa45 100644
> > --- a/libavformat/avformat.c
> > +++ b/libavformat/avformat.c
> > @@ -235,6 +235,43 @@ int ff_stream_side_data_copy(AVStream *dst, const AVStream *src)
> >      return 0;
> >  }
> >
> > +int ff_stream_params_copy(AVStream *dst, const AVStream *src)
> > +{
> > +    int ret;
> > +
> > +    dst->id                  = src->id;
> > +    dst->time_base           = src->time_base;
> > +    dst->start_time          = src->start_time;
> > +    dst->duration            = src->duration;
> > +    dst->nb_frames           = src->nb_frames;
> > +    dst->disposition         = src->disposition;
> > +    dst->discard             = src->discard;
> > +    dst->sample_aspect_ratio = src->sample_aspect_ratio;
> > +    dst->avg_frame_rate      = src->avg_frame_rate;
> > +    dst->event_flags         = src->event_flags;
> > +    dst->r_frame_rate        = src->r_frame_rate;
> > +    dst->pts_wrap_bits       = src->pts_wrap_bits;
> > +
> > +    av_dict_free(&dst->metadata);
> > +    ret = av_dict_copy(&dst->metadata, src->metadata, 0);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    ret = avcodec_parameters_copy(dst->codecpar, src->codecpar);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    ret = ff_stream_side_data_copy(dst, src);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    ret = av_packet_ref(&dst->attached_pic, &src->attached_pic);
>
> This will allocate a buffer of size AV_INPUT_BUFFER_PADDING_SIZE in
> dst->attached_pic (and set the size of the data of said packet to 0) if
> the size of the data of src->attached_pic is zero (in particular, if it
> is truely blank). This is not desired.

As I understand it, this behavior is triggered if src->attached_pic is
not null and not ref-counted. Is that right? If so, are there
circumstances where src->attached_pic is not ref-counted?
ff_add_attached_pic() seems to add ref-counted data.

av_packet_ref() creates a ref-counted buffer if the src packet does
not contain one. Changing that behavior would require duplicating the
mechanics of av_packet_ref().

... or maybe there is a much simpler approach?

>
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    return 0;
> > +}
> > +
> >  AVProgram *av_new_program(AVFormatContext *ac, int id)
> >  {
> >      AVProgram *program = NULL;
> > diff --git a/libavformat/fifo.c b/libavformat/fifo.c
> > index ead2bdc5cf..fef116d040 100644
> > --- a/libavformat/fifo.c
> > +++ b/libavformat/fifo.c
> > @@ -509,7 +509,7 @@ static int fifo_mux_init(AVFormatContext *avf, const AVOutputFormat *oformat,
> >          if (!st)
> >              return AVERROR(ENOMEM);
> >
> > -        ret = ff_stream_encode_params_copy(st, avf->streams[i]);
> > +        ret = ff_stream_params_copy(st, avf->streams[i]);
> >          if (ret < 0)
> >              return ret;
> >      }
> > diff --git a/libavformat/internal.h b/libavformat/internal.h
> > index b6b8fbf56f..774ff57698 100644
> > --- a/libavformat/internal.h
> > +++ b/libavformat/internal.h
> > @@ -625,6 +625,16 @@ enum AVCodecID ff_get_pcm_codec_id(int bps, int flt, int be, int sflags);
> >   */
> >  int ff_stream_side_data_copy(AVStream *dst, const AVStream *src);
> >
> > +/**
> > + * Copy all stream parameters from source to destination stream, with the
> > + * exception of the index field, which is usually set by avformat_new_stream().
> > + *
> > + * @param dst pointer to destination AVStream
> > + * @param src pointer to source AVStream
> > + * @return >=0 on success, AVERROR code on error
> > + */
> > +int ff_stream_params_copy(AVStream *dst, const AVStream *src);
> > +
> >  /**
> >   * Wrap ffurl_move() and log if error happens.
> >   *
> > diff --git a/libavformat/mux.h b/libavformat/mux.h
> > index c01da82194..1bfcaf795f 100644
> > --- a/libavformat/mux.h
> > +++ b/libavformat/mux.h
> > @@ -113,15 +113,6 @@ int ff_format_shift_data(AVFormatContext *s, int64_t read_start, int shift_size)
> >   */
> >  int ff_format_output_open(AVFormatContext *s, const char *url, AVDictionary **options);
> >
> > -/**
> > - * Copy encoding parameters from source to destination stream
> > - *
> > - * @param dst pointer to destination AVStream
> > - * @param src pointer to source AVStream
> > - * @return >=0 on success, AVERROR code on error
> > - */
> > -int ff_stream_encode_params_copy(AVStream *dst, const AVStream *src);
> > -
> >  /**
> >   * Parse creation_time in AVFormatContext metadata if exists and warn if the
> >   * parsing fails.
> > diff --git a/libavformat/mux_utils.c b/libavformat/mux_utils.c
> > index eb8ea3d560..2fa2ab5b0f 100644
> > --- a/libavformat/mux_utils.c
> > +++ b/libavformat/mux_utils.c
> > @@ -121,34 +121,6 @@ int ff_format_output_open(AVFormatContext *s, const char *url, AVDictionary **op
> >      return 0;
> >  }
> >
> > -int ff_stream_encode_params_copy(AVStream *dst, const AVStream *src)
> > -{
> > -    int ret;
> > -
> > -    dst->id                  = src->id;
> > -    dst->time_base           = src->time_base;
> > -    dst->nb_frames           = src->nb_frames;
> > -    dst->disposition         = src->disposition;
> > -    dst->sample_aspect_ratio = src->sample_aspect_ratio;
> > -    dst->avg_frame_rate      = src->avg_frame_rate;
> > -    dst->r_frame_rate        = src->r_frame_rate;
> > -
> > -    av_dict_free(&dst->metadata);
> > -    ret = av_dict_copy(&dst->metadata, src->metadata, 0);
> > -    if (ret < 0)
> > -        return ret;
> > -
> > -    ret = avcodec_parameters_copy(dst->codecpar, src->codecpar);
> > -    if (ret < 0)
> > -        return ret;
> > -
> > -    ret = ff_stream_side_data_copy(dst, src);
> > -    if (ret < 0)
> > -        return ret;
> > -
> > -    return 0;
> > -}
> > -
> >  int ff_parse_creation_time_metadata(AVFormatContext *s, int64_t *timestamp, int return_seconds)
> >  {
> >      AVDictionaryEntry *entry;
> > diff --git a/libavformat/segment.c b/libavformat/segment.c
> > index fa435d9f32..a8f3e94714 100644
> > --- a/libavformat/segment.c
> > +++ b/libavformat/segment.c
> > @@ -169,7 +169,7 @@ static int segment_mux_init(AVFormatContext *s)
> >
> >          if (!(st = avformat_new_stream(oc, NULL)))
> >              return AVERROR(ENOMEM);
> > -        ret = ff_stream_encode_params_copy(st, ist);
> > +        ret = ff_stream_params_copy(st, ist);
> >          if (ret < 0)
> >              return ret;
> >          opar = st->codecpar;
> > diff --git a/libavformat/tee.c b/libavformat/tee.c
> > index f1f2a9d2a5..dbfad604d0 100644
> > --- a/libavformat/tee.c
> > +++ b/libavformat/tee.c
> > @@ -289,7 +289,7 @@ static int open_slave(AVFormatContext *avf, char *slave, TeeSlave *tee_slave)
> >              goto end;
> >          }
> >
> > -        ret = ff_stream_encode_params_copy(st2, st);
> > +        ret = ff_stream_params_copy(st2, st);
> >          if (ret < 0)
> >              goto end;
> >      }
> > diff --git a/libavformat/webm_chunk.c b/libavformat/webm_chunk.c
> > index d69db3a004..39f21fce7a 100644
> > --- a/libavformat/webm_chunk.c
> > +++ b/libavformat/webm_chunk.c
> > @@ -94,7 +94,7 @@ static int webm_chunk_init(AVFormatContext *s)
> >      if (!(st = avformat_new_stream(oc, NULL)))
> >          return AVERROR(ENOMEM);
> >
> > -    if ((ret = ff_stream_encode_params_copy(st, ost)) < 0)
> > +    if ((ret = ff_stream_params_copy(st, ost)) < 0)
> >          return ret;
> >
> >      if (wc->http_method)
>
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