[FFmpeg-devel] [PATCH] avformat/utils: fix seek failed

[Marton Balint]

On Thu, 31 Dec 2020, Zhao Zhili wrote:

> Rounding min_ts towards +infinity and max_ts towards -infinity can
> make ts out of the [min_ts, max_ts] range, and then leads to seek
> failure. For example,

I think this is intentional to adhere to the docs of the function:

"Seeking will be done so that the point from which all active streams
can be presented successfully will be closest to ts and within 
min/max_ts."

If you round down min_ts, you might return a packet with a timestamp less 
than the original min_ts, which contradicts the documentation.

Regards,
Marton


>
> max_ts = ts = -25057
> time_base = (num = 1, den = 14112000)
>
> After rescale, ts = -353604, and max_ts = -353605.
> ---
> libavformat/utils.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 503e583ad0..69a0f901b2 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -2500,10 +2500,10 @@ int avformat_seek_file(AVFormatContext *s, int stream_index, int64_t min_ts,
>             ts = av_rescale_q(ts, AV_TIME_BASE_Q, time_base);
>             min_ts = av_rescale_rnd(min_ts, time_base.den,
>                                     time_base.num * (int64_t)AV_TIME_BASE,
> -                                    AV_ROUND_UP   | AV_ROUND_PASS_MINMAX);
> +                                    AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
>             max_ts = av_rescale_rnd(max_ts, time_base.den,
>                                     time_base.num * (int64_t)AV_TIME_BASE,
> -                                    AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
> +                                    AV_ROUND_UP | AV_ROUND_PASS_MINMAX);
>             stream_index = 0;
>         }
> 
> -- 
> 2.28.0
>
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