Re: [FFmpeg-devel] [PATCH v5 1/2] avformat: refactor ff_stream_encode_params_copy() to ff_stream_params_copy()

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

On Thu, Aug 4, 2022 at 3:22 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> Pierre-Anthony Lemieux:
> > On Thu, Aug 4, 2022 at 10:15 AM Andreas Rheinhardt
> > <andreas.rheinhardt@outlook.com> wrote:
> >>
> >> Pierre-Anthony Lemieux:
> >>> On Thu, Aug 4, 2022 at 9:53 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
> >>>>>  * the attached_pic if its size is 0
> >>>>>
> >>>>> Addresses http://ffmpeg.org/pipermail/ffmpeg-devel/2022-August/299514.html
> >>>>>
> >>>>> ---
> >>>>>  libavformat/avformat.c   | 40 ++++++++++++++++++++++++++++++++++++++++
> >>>>>  libavformat/fifo.c       |  2 +-
> >>>>>  libavformat/internal.h   | 12 ++++++++++++
> >>>>>  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, 56 insertions(+), 41 deletions(-)
> >>>>>
> >>>>> diff --git a/libavformat/avformat.c b/libavformat/avformat.c
> >>>>> index 30d6ea6a49..242187c359 100644
> >>>>> --- a/libavformat/avformat.c
> >>>>> +++ b/libavformat/avformat.c
> >>>>> @@ -235,6 +235,46 @@ 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;
> >>>>> +
> >>>>> +    av_packet_unref(&dst->attached_pic);
> >>>>> +    if (src->attached_pic.size > 0) {
> >>>>> +        ret = av_packet_ref(&dst->attached_pic, &src->attached_pic);
> >>>>> +        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..87a00bbae3 100644
> >>>>> --- a/libavformat/internal.h
> >>>>> +++ b/libavformat/internal.h
> >>>>> @@ -625,6 +625,18 @@ 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()
> >>>>> + *  * the attached_pic field, if attached_pic.size is 0 or less
> >>>>> + *
> >>>>> + * @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)
> >>>>
> >>>> Looking at these callers shows that they all have one thing in common:
> >>>> They create a stream and immediately afterwards copy stream parameters.
> >>>> The caller that you intend to add in #2 does the same. How about we make
> >>>> a function that is equivalent to
> >>>> avformat_new_stream+ff_stream_params_copy above and use that? (But
> >>>> please leave ff_stream_params_copy as it is in the form of a static
> >>>> function.)
> >>>
> >>> avformat_clone_stream()?
> >>>
> >>
> >> I was not thinking about a public function. But clone_stream sounds good.
> >
> > Something like this?
> >
> > int ff_stream_clone(AVFormatContext *s, AVStream **dst, const AVStream *src)
> > {
> >     AVStream *st;
> >     int ret;
> >
> >     st = avformat_new_stream(s, NULL);
> >     if (!st)
> >         return AVERROR(ENOMEM);
> >
> >     ret = stream_params_copy(st, src);
> >     if (ret < 0)
> >         return ret;
> >
> >     *dst = st;
> >
> >     return 0;
> > }
> >
>
> I'd use AVStream *ff_stream_clone(AVFormatContext *dst_ctx, const
> AVStream *src);

How does one recover a pointer to the stream that was just created?
Isn't there a potential race condition with dst_ctx[nb_streams - 1]?

>
> - Andreas
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