[FFmpeg-devel] [PATCH] avformat/mov: fix timecode with rounded down tmcd nb_frames

[Marton Balint]

On Sun, 1 May 2022, Marton Balint wrote:

> Regression since 8dd5bb728038f21d17ec789e21d65fe8f3f364a6.
> Fixes ticket #5978.

Will apply tomorrow.

Regards,
Marton

>
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
> libavformat/mov.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 0f63d997fc..dfd5720bf4 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -8038,12 +8038,13 @@ static int mov_read_timecode_track(AVFormatContext *s, AVStream *st)
>     int64_t cur_pos = avio_tell(sc->pb);
>     int64_t value;
>     AVRational tc_rate = st->avg_frame_rate;
> +    int tmcd_nb_frames = sc->tmcd_nb_frames;
>     int rounded_tc_rate;
>
>     if (!sti->nb_index_entries)
>         return -1;
>
> -    if (!tc_rate.num || !tc_rate.den || !sc->tmcd_nb_frames)
> +    if (!tc_rate.num || !tc_rate.den || !tmcd_nb_frames)
>         return -1;
>
>     avio_seek(sc->pb, sti->index_entries->pos, SEEK_SET);
> @@ -8060,9 +8061,15 @@ static int mov_read_timecode_track(AVFormatContext *s, AVStream *st)
>      * format). */
>
>     /* 60 fps content have tmcd_nb_frames set to 30 but tc_rate set to 60, so
> -     * we multiply the frame number with the quotient. */
> +     * we multiply the frame number with the quotient.
> +     * See tickets #9492, #9710. */
>     rounded_tc_rate = (tc_rate.num + tc_rate.den / 2) / tc_rate.den;
> -    value = av_rescale(value, rounded_tc_rate, sc->tmcd_nb_frames);
> +    /* Work around files where tmcd_nb_frames is rounded down from frame rate
> +     * instead of up. See ticket #5978. */
> +    if (tmcd_nb_frames == tc_rate.num / tc_rate.den &&
> +        s->strict_std_compliance < FF_COMPLIANCE_STRICT)
> +        tmcd_nb_frames = rounded_tc_rate;
> +    value = av_rescale(value, rounded_tc_rate, tmcd_nb_frames);
>
>     parse_timecode_in_framenum_format(s, st, value, flags);
>
> -- 
> 2.34.1
>
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