[FFmpeg-devel] [PATCH] lavfi/libplacebo: properly handle EOF

[Niklas Haas]

On Sun, 21 May 2023 13:13:52 +0200 Niklas Haas <ffmpeg at haasn.xyz> wrote:
> From: Niklas Haas <git at haasn.dev>
> 
> The current code relied on pl_queue eventually returning EOF back to the
> caller, which didn't work in all situations (e.g. single frame input).
> Also, the current code assumed that ff_inlink_acknowledge_status only
> fired once, which was patently not true, as the above edge cases
> demonstrated.
> 
> Solve both issues by keeping track of the acknowledged link status and
> forwarding it (instead of trying to probe the pl_queue again) in the
> event that we run out of queued input frames, as well as (in CFR mode)
> when we pass the indicated status PTS.
> ---
>  libavfilter/vf_libplacebo.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
> index 94e49aa4652..6ce0f6263e4 100644
> --- a/libavfilter/vf_libplacebo.c
> +++ b/libavfilter/vf_libplacebo.c
> @@ -131,6 +131,8 @@ typedef struct LibplaceboContext {
>  
>      /* filter state */
>      AVFifo *out_pts; ///< timestamps of wanted output frames
> +    int64_t status_pts;
> +    int status;
>  
>      /* settings */
>      char *out_format_string;
> @@ -805,19 +807,12 @@ static int libplacebo_activate(AVFilterContext *ctx)
>      if (ret < 0)
>          return ret;
>  
> -    if (ff_inlink_acknowledge_status(inlink, &status, &pts)) {
> +    if (!s->status && ff_inlink_acknowledge_status(inlink, &status, &pts)) {
>          pts = av_rescale_q_rnd(pts, inlink->time_base, outlink->time_base,
>                                 AV_ROUND_UP);
> -        if (status == AVERROR_EOF) {
> -            /* Signal EOF to pl_queue, and enqueue this output frame to
> -             * make sure we see PL_QUEUE_EOF returned eventually */
> -            pl_queue_push(s->queue, NULL);
> -            if (!s->fps.num)
> -                av_fifo_write(s->out_pts, &pts, 1);
> -        } else {
> -            ff_outlink_set_status(outlink, status, pts);
> -            return 0;
> -        }
> +        pl_queue_push(s->queue, NULL); /* Signal EOF to pl_queue */
> +        s->status = status;
> +        s->status_pts = pts;
>      }
>  
>      if (ff_outlink_frame_wanted(outlink)) {
> @@ -827,7 +822,17 @@ static int libplacebo_activate(AVFilterContext *ctx)
>          if (s->fps.num) {
>              pts = outlink->frame_count_out;
>          } else if (av_fifo_peek(s->out_pts, &pts, 1, 0) < 0) {
> -            ff_inlink_request_frame(inlink);
> +            /* No frames queued */
> +            if (s->status) {
> +                pts = s->status_pts;
> +            } else {
> +                ff_inlink_request_frame(inlink);
> +                return 0;
> +            }
> +        }
> +
> +        if (s->status && pts >= s->status_pts) {
> +            ff_outlink_set_status(outlink, s->status, s->status_pts);
>              return 0;
>          }
>  
> -- 
> 2.40.1
> 

Merged as c00fd025587fc8f028cda2c36f0061070fe91a35