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 4:13 PM Andreas Rheinhardt
<andreas.rheinhardt@outlook.com> wrote:
>
> Pierre-Anthony Lemieux:
> > 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]?
> >
>
> ?
> 1. The function is supposed to return the stream just created; just like
> avformat_new_stream does.

Oh. I missed the return of AVStream*.

We lose the error code returned by stream_params_copy(). Works for me though.

> 2. If there are multiple threads adding streams to dst_ctx, we'd already
> be screwed anyway (avformat_new_stream does not use any lock).
>
> - Andreas
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