[vlc-devel] [PATCH] vout: fix low framerate stuttering

[Steve Lhomme]

It seems that you are overriding more cases than the "refresh" one. What 
are the consequences when first and drop_next_frame are false ?

On 2019-08-06 15:07, Romain Vimont wrote:
> In ThreadDisplayPicture(), when "refresh" was true, the output parameter
> deadline was not written and the function returned a non-zero value.
> 
> As a consequence, in video_output.c:Thread(), the next loop iteration
> waited for the max deadline (100ms). When the following frame target
> date was before this deadline, the video was stuttering.
> 
> To avoid the problem, write the deadline before returning from
> ThreadDisplayPicture(), so that Thread() does not wait more than
> expected.
> 
> Since an existing frame is refreshed only every 80ms
> (VOUT_REDISPLAY_DELAY), this happened only on low framerate videos
> (<12.5 fps). Otherwise, "refresh" was always false and the problem never
> occurred.
> ---
> You can test with this video at 10fps: https://tmp.rom1v.com/10fps.mp4
> 
>   src/video_output/video_output.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
> index 4a2cde9f98..ef0d9488ae 100644
> --- a/src/video_output/video_output.c
> +++ b/src/video_output/video_output.c
> @@ -1243,13 +1243,14 @@ static int ThreadDisplayPicture(vout_thread_t *vout, vlc_tick_t *deadline)
>       }
>       bool force_refresh = !drop_next_frame && refresh;
>   
> +    if (!frame_by_frame) {
> +        if (date_refresh != VLC_TICK_INVALID)
> +            *deadline = date_refresh;
> +        if (date_next != VLC_TICK_INVALID && date_next < *deadline)
> +            *deadline = date_next;
> +    }
> +
>       if (!first && !refresh && !drop_next_frame) {
> -        if (!frame_by_frame) {
> -            if (date_refresh != VLC_TICK_INVALID)
> -                *deadline = date_refresh;
> -            if (date_next != VLC_TICK_INVALID && date_next < *deadline)
> -                *deadline = date_next;
> -        }
>           return VLC_EGENERIC;
>       }
>   
> -- 
> 2.23.0.rc1
> 
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