[FFmpeg-devel] [PATCH] lavfi/color: cache and reuse colored picture in context

[Nicolas George]

Le duodi 12 thermidor, an CCXX, Stefano Sabatini a écrit :
> Avoid to avoid to fill the same picture again and again with the same

"Avoid to avoid"?

> content.
> Optimize computation, and provides an example for the use of the
> AV_PERM_REUSE permission flag.
> ---
>  libavfilter/vsrc_color.c |   34 ++++++++++++++++++++++------------
>  1 files changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/libavfilter/vsrc_color.c b/libavfilter/vsrc_color.c
> index ca336ac..9d78a32 100644
> --- a/libavfilter/vsrc_color.c
> +++ b/libavfilter/vsrc_color.c
> @@ -45,6 +45,7 @@ typedef struct {
>      uint64_t pts;
>      FFDrawContext draw;
>      FFDrawColor color;
> +    AVFilterBufferRef *picref;  ///< cached reference containing the painted picture
>  } ColorContext;
>  
>  #define OFFSET(x) offsetof(ColorContext, x)
> @@ -92,6 +93,12 @@ end:
>      return ret;
>  }
>  
> +static av_cold void color_uninit(AVFilterContext *ctx)
> +{
> +    ColorContext *color = ctx->priv;
> +    avfilter_unref_bufferp(&color->picref);
> +}
> +
>  static int query_formats(AVFilterContext *ctx)
>  {
>      ff_set_common_formats(ctx, ff_draw_supported_pixel_formats(0));
> @@ -124,18 +131,24 @@ static int color_config_props(AVFilterLink *inlink)
>  static int color_request_frame(AVFilterLink *link)
>  {
>      ColorContext *color = link->src->priv;
> -    AVFilterBufferRef *picref = ff_get_video_buffer(link, AV_PERM_WRITE, color->w, color->h);
>      AVFilterBufferRef *buf_out;
>      int ret;
>  
> -    if (!picref)
> -        return AVERROR(ENOMEM);
> -
> -    picref->video->sample_aspect_ratio = (AVRational) {1, 1};
> -    picref->pts = color->pts++;
> -    picref->pos = -1;
> +    if (!color->picref) {
> +        color->picref =
> +            ff_get_video_buffer(link, AV_PERM_WRITE|AV_PERM_REUSE,
> +                                color->w, color->h);
> +        if (!color->picref)
> +            return AVERROR(ENOMEM);
> +        ff_fill_rectangle(&color->draw, &color->color,
> +                          color->picref->data, color->picref->linesize,
> +                          0, 0, color->w, color->h);
> +        color->picref->video->sample_aspect_ratio = (AVRational) {1, 1};
> +        color->picref->pos = -1;
> +    }
>  
> -    buf_out = avfilter_ref_buffer(picref, ~0);
> +    color->picref->pts = color->pts++;

> +    buf_out = avfilter_ref_buffer(color->picref, ~0);

If you do not remove WRITE, the next filter may write in the original buffer
and its result will stay on all frames. I predict that "drawtext=x=t*10:..."
would leave a sludge.

PRESERVE may help avoid a few useless copies, but that I am not completely
sure about.

(Speaking of which, your opinion in the thread "Understanding lavfi's
permissions system" would be appreciated.)

>      if (!buf_out) {
>          ret = AVERROR(ENOMEM);
>          goto fail;
> @@ -145,8 +158,6 @@ static int color_request_frame(AVFilterLink *link)
>      if (ret < 0)
>          goto fail;
>  
> -    ff_fill_rectangle(&color->draw, &color->color, picref->data, picref->linesize,
> -                      0, 0, color->w, color->h);
>      ret = ff_draw_slice(link, 0, color->h, 1);
>      if (ret < 0)
>          goto fail;
> @@ -154,8 +165,6 @@ static int color_request_frame(AVFilterLink *link)
>      ret = ff_end_frame(link);
>  
>  fail:
> -    avfilter_unref_buffer(picref);
> -
>      return ret;
>  }
>  
> @@ -165,6 +174,7 @@ AVFilter avfilter_vsrc_color = {
>  
>      .priv_size = sizeof(ColorContext),
>      .init      = color_init,
> +    .uninit    = color_uninit,
>  
>      .query_formats = query_formats,
>  

Regards,

-- 
  Nicolas George
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