[FFmpeg-devel] [patch] Fade to correct CCIR601/709 black level

[Stefano Sabatini]

On date Tuesday 2011-11-01 20:57:35 +0000, Mark Himsley encoded:
> On 01/11/11 20:33, Mark Himsley wrote:
> 
> [...]
> 
> >+                *p =  ((*p - fade->black_level) * fade->factor + fade->black_level_scaled)>>  16;
> 
> Strange formatting    ^^^^
> 
> New patch that's tidier.
> 
> -- 
> Mark
> 

> diff --git a/libavfilter/vf_fade.c b/libavfilter/vf_fade.c
> index 6c2a23d..5032019 100644
> --- a/libavfilter/vf_fade.c
> +++ b/libavfilter/vf_fade.c
> @@ -27,11 +27,13 @@
>  
>  #include "libavutil/pixdesc.h"
>  #include "avfilter.h"
> +#include "internal.h"
>  
>  typedef struct {
>      int factor, fade_per_frame;
>      unsigned int frame_index, start_frame, stop_frame;
>      int hsub, vsub, bpp;
> +    unsigned int black_level, black_level_scaled;
>  } FadeContext;
>  
>  static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
> @@ -82,6 +84,13 @@ static int query_formats(AVFilterContext *ctx)
>      return 0;
>  }
>  
> +const static enum PixelFormat studio_level_pix_fmts[] = {
> +    PIX_FMT_YUV444P,  PIX_FMT_YUV422P,  PIX_FMT_YUV420P,
> +    PIX_FMT_YUV411P,  PIX_FMT_YUV410P,
> +    PIX_FMT_YUV440P,
> +    PIX_FMT_NONE
> +};
> +
>  static int config_props(AVFilterLink *inlink)
>  {
>      FadeContext *fade = inlink->dst->priv;
> @@ -91,6 +100,11 @@ static int config_props(AVFilterLink *inlink)
>      fade->vsub = pixdesc->log2_chroma_h;
>  
>      fade->bpp = av_get_bits_per_pixel(pixdesc) >> 3;
> +
> +    fade->black_level = ff_fmt_is_in(inlink->format, studio_level_pix_fmts) ? 16 : 0;
> +    /* 32768 = 1 << 15, it is an integer representation
> +     * of 0.5 and is for rounding. */
> +    fade->black_level_scaled = (fade->black_level << 16) + 32768;
>      return 0;
>  }
>  
> @@ -106,10 +120,8 @@ static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
>          for (i = 0; i < h; i++) {
>              p = outpic->data[0] + (y+i) * outpic->linesize[0];
>              for (j = 0; j < inlink->w * fade->bpp; j++) {
> -                /* fade->factor is using 16 lower-order bits for decimal
> -                 * places. 32768 = 1 << 15, it is an integer representation
> -                 * of 0.5 and is for rounding. */
> -                *p = (*p * fade->factor + 32768) >> 16;
> +                /* fade->factor is using 16 lower-order bits for decimal places. */
> +                *p = ((*p - fade->black_level) * fade->factor + fade->black_level_scaled) >> 16;
>                  p++;
>              }
>          }

Looks fine to me, I'll apply it soon if I see no other comments in a day or
so.
Thanks
-- 
FFmpeg = Fundamental and Friendly Multimedia Ponderous Eretic Game