[FFmpeg-devel] [PATCH] lavf: consider codec timebase for framerate detection

[wm4]

On Tue, 23 May 2017 13:36:51 +0200
wm4 <nfxjfg at googlemail.com> wrote:

> Fixes detection of some TV sample as 24.5 FPS. With the patch applied,
> it's detected as 25 FPS.
> ---
>  libavformat/utils.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index fbd8b58ac2..778a82aeee 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -3903,6 +3903,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
>                  st->info->codec_info_duration) {
>                  int best_fps      = 0;
>                  double best_error = 0.01;
> +                AVRational codec_frame_rate = av_inv_q(avctx->time_base);
>  
>                  if (st->info->codec_info_duration        >= INT64_MAX / st->time_base.num / 2||
>                      st->info->codec_info_duration_fields >= INT64_MAX / st->time_base.den ||
> @@ -3924,6 +3925,27 @@ FF_ENABLE_DEPRECATION_WARNINGS
>                          best_fps   = std_fps.num;
>                      }
>                  }
> +                if (avctx->ticks_per_frame > 0)
> +                    codec_frame_rate.num /= avctx->ticks_per_frame;
> +                for (j = 0; j < MAX_STD_TIMEBASES; j++) {
> +                    AVRational std_fps = { get_std_framerate(j), 12 * 1001 };
> +                    double error       = fabs(av_q2d(st->avg_frame_rate) /
> +                                              av_q2d(std_fps) - 1);
> +
> +                    if (error < best_error) {
> +                        best_error = error;
> +                        best_fps   = std_fps.num;
> +                    }
> +
> +                    if (codec_frame_rate.num > 0 && codec_frame_rate.den > 0) {
> +                        error       = fabs(av_q2d(codec_frame_rate) /
> +                                           av_q2d(std_fps) - 1);
> +                        if (error < best_error) {
> +                            best_error = error;
> +                            best_fps   = std_fps.num;
> +                        }
> +                    }
> +                }
>                  if (best_fps)
>                      av_reduce(&st->avg_frame_rate.num, &st->avg_frame_rate.den,
>                                best_fps, 12 * 1001, INT_MAX);

Oops, the patch got mangled. The loop above the additions should have
been replaced. This should compute the same result anyway, and I'll
remove it before pushing.