[FFmpeg-devel] [PATCH 07/12] avformat/mxfdec: compute sample_count for all streams on seek

[Tomas Härdin]

sön 2018-06-10 klockan 12:36 +0200 skrev Marton Balint:
> sample_count will be used for per-stream current_edit_unit.
> 
> > Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  libavformat/mxfdec.c | 39 +++++++++++++++++----------------------
>  1 file changed, 17 insertions(+), 22 deletions(-)
> 
> diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> index 8e099164aa..0f4cc9c3a3 100644
> --- a/libavformat/mxfdec.c
> +++ b/libavformat/mxfdec.c
> @@ -3214,29 +3214,32 @@ static int64_t mxf_set_current_edit_unit(MXFContext *mxf, int64_t current_offset
>      return next_ofs;
>  }
>  
> -static int mxf_compute_sample_count(MXFContext *mxf, int stream_index,
> -                                    int64_t edit_unit, uint64_t *sample_count)
> +static int64_t mxf_compute_sample_count(MXFContext *mxf, AVStream *st,
> +                                        int64_t edit_unit)
>  {
>      int i, total = 0, size = 0;
> -    AVStream *st = mxf->fc->streams[stream_index];
>      MXFTrack *track = st->priv_data;
>      AVRational time_base = av_inv_q(track->edit_rate);
>      AVRational sample_rate = av_inv_q(st->time_base);
>      const MXFSamplesPerFrame *spf = NULL;
> +    int64_t sample_count;
> +
> +    // For non-audio sample_count equals current edit unit
> +    if (st->codecpar->codec_type != AVMEDIA_TYPE_AUDIO)
> +        return edit_unit;
>  
>      if ((sample_rate.num / sample_rate.den) == 48000)
>          spf = ff_mxf_get_samples_per_frame(mxf->fc, time_base);
>      if (!spf) {
>          int remainder = (sample_rate.num * time_base.num) %
>                          (time_base.den * sample_rate.den);
> -        *sample_count = av_rescale_q(edit_unit, sample_rate, track->edit_rate);
>          if (remainder)
>              av_log(mxf->fc, AV_LOG_WARNING,
>                     "seeking detected on stream #%d with time base (%d/%d) and "
>                     "sample rate (%d/%d), audio pts won't be accurate.\n",
> -                   stream_index, time_base.num, time_base.den,
> +                   st->index, time_base.num, time_base.den,
>                     sample_rate.num, sample_rate.den);
> -        return 0;
> +        return av_rescale_q(edit_unit, sample_rate, track->edit_rate);
>      }
>  
>      while (spf->samples_per_frame[size]) {
> @@ -3246,12 +3249,12 @@ static int mxf_compute_sample_count(MXFContext *mxf, int stream_index,
>  
>      av_assert2(size);
>  
> -    *sample_count = (edit_unit / size) * (uint64_t)total;
> +    sample_count = (edit_unit / size) * (uint64_t)total;
>      for (i = 0; i < edit_unit % size; i++) {
> -        *sample_count += spf->samples_per_frame[i];
> +        sample_count += spf->samples_per_frame[i];
>      }
>  
> -    return 0;
> +    return sample_count;
>  }
>  
>  static int mxf_set_audio_pts(MXFContext *mxf, AVCodecParameters *par,
> @@ -3587,19 +3590,11 @@ static int mxf_read_seek(AVFormatContext *s, int stream_index, int64_t sample_ti
>      for (i = 0; i < s->nb_streams; i++) {
>          AVStream *cur_st = s->streams[i];
>          MXFTrack *cur_track = cur_st->priv_data;
> -        if (cur_st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
> -            int64_t track_edit_unit;
> -            if (st != cur_st && mxf_get_next_track_edit_unit(mxf, cur_track, seekpos, &track_edit_unit) >= 0) {
> -                cur_track->sample_count = av_rescale_q(track_edit_unit,
> -                                                       av_inv_q(cur_track->edit_rate),
> -                                                       cur_st->time_base);
> -            } else {
> -                uint64_t current_sample_count = 0;
> -                ret = mxf_compute_sample_count(mxf, i, sample_time, &current_sample_count);
> -                if (ret < 0)
> -                    return ret;
> -                cur_track->sample_count = current_sample_count;
> -            }
> +        if (cur_track) {
> +            int64_t track_edit_unit = sample_time;
> +            if (st != cur_st)
> +                mxf_get_next_track_edit_unit(mxf, cur_track, seekpos, &track_edit_unit);
> +            cur_track->sample_count = mxf_compute_sample_count(mxf, cur_st, track_edit_unit);
>          }
>      }
>      return 0;

Looks OK enough, but I know seeking logic can get extremely hairy and
tends to be brittle

/Tomas