[FFmpeg-devel] [PATCH v2] lavf/movenc: suggest video_track_timescale for invalid timescale

[Carl Eugen Hoyos]

2016-10-11 21:06 GMT+02:00 Josh de Kock <josh at itanimul.li>:
> Fixes ticket #5882.

I don't object but I don't think it is correct.

> While it doesn't automatically set the timescale
> for the user as that would destroy data without prompt, it will tell
> the user how they could set the timescale (as this is mostly likely
> what they want).
>
> Signed-off-by: Josh de Kock <josh at itanimul.li>
> ---
>
>>Would it be useful to print the max duration?
>  I'm not entirely sure, open to suggestions though.
>
>  libavformat/movenc.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index d7c7158..6bada25 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -5677,11 +5677,16 @@ static int mov_write_header(AVFormatContext *s)
>                  ret = AVERROR(EINVAL);
>                  goto error;
>              }
> -            if (track->mode == MODE_MOV && track->timescale > 100000)
> +            if (track->mode == MODE_MOV && track->timescale > 100000) {
> +                /* NOTE: forcing setting the suggested timescale manually means ffmpeg won't destroy
> +                 * timestamps without explicit instruction. */

> +                unsigned int suggested = (unsigned int)av_rescale(st->time_base.den, 1000, st->time_base.num);

If we go this way (I am not completely convinced about it), we definitely need
a heuristic that suggests 24000 for 10000000/417083 fps and 30000 if applicable.

>                  av_log(s, AV_LOG_WARNING,
>                         "WARNING codec timebase is very high. If duration is too long,\n"
>                         "file may not be playable by quicktime. Specify a shorter timebase\n"
> -                       "or choose different container.\n");
> +                       "or choose different container. Using -video_track_timescale %d\n"
> +                       "may fix this issue.\n", suggested);

I believe this should also suggest to "force a sane framerate" as an
alternative.

Suggesting video_track_timescale is very useful, thank you!

Carl Eugen