Re: [FFmpeg-devel] [PATCH] avfilter/vf_thumbnail: support high bit depth formats

[Niklas Haas <ffmpeg@haasn.xyz>]

On Sun, 15 Jun 2025 05:44:43 +0200 Andreas Rheinhardt <andreas.rheinhardt@outlook.com> wrote:
> Niklas Haas:
> > From: Niklas Haas <git@haasn.dev>
> >
> > Implementation is the same as 8 bit formats, just right shifted to 8 bits.
> >
> > It's worth pointing out that this also works for HDR formats (and even DV),
> > because the underlying implementation is just trying to minimize the histogram
> > difference. If anything, using a HDR format will result in a *more* accurate
> > detection, because HDR formats tend to be more perceptually uniform.
> > ---
> >  libavfilter/vf_thumbnail.c | 54 +++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 53 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c
> > index 90125a879c..f353f0495c 100644
> > --- a/libavfilter/vf_thumbnail.c
> > +++ b/libavfilter/vf_thumbnail.c
> > @@ -53,6 +53,7 @@ typedef struct ThumbContext {
> >
> >      int planewidth[4];
> >      int planeheight[4];
> > +    int bitdepth;
> >  } ThumbContext;
> >
> >  #define OFFSET(x) offsetof(ThumbContext, x)
> > @@ -193,7 +194,23 @@ static int do_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
> >              p += frame->linesize[0];
> >          }
> >          break;
> > -    default:
> > +
> > +    case AV_PIX_FMT_YUV410P:
> > +    case AV_PIX_FMT_YUV411P:
> > +    case AV_PIX_FMT_YUV420P:
> > +    case AV_PIX_FMT_YUV422P:
> > +    case AV_PIX_FMT_YUV440P:
> > +    case AV_PIX_FMT_YUV444P:
> > +    case AV_PIX_FMT_YUVJ420P:
> > +    case AV_PIX_FMT_YUVJ422P:
> > +    case AV_PIX_FMT_YUVJ440P:
> > +    case AV_PIX_FMT_YUVJ444P:
> > +    case AV_PIX_FMT_YUVJ411P:
> > +    case AV_PIX_FMT_YUVA420P:
> > +    case AV_PIX_FMT_YUVA422P:
> > +    case AV_PIX_FMT_YUVA444P:
> > +    case AV_PIX_FMT_GBRP:
> > +    case AV_PIX_FMT_GBRAP:
> >          for (int plane = 0; plane < 3; plane++) {
> >              const int slice_start = (s->planeheight[plane] * jobnr) / nb_jobs;
> >              const int slice_end = (s->planeheight[plane] * (jobnr+1)) / nb_jobs;
> > @@ -209,6 +226,25 @@ static int do_slice(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
> >              }
> >          }
> >          break;
> > +
> > +    default:
> > +        for (int plane = 0; plane < 3; plane++) {
> > +            const int slice_start = (s->planeheight[plane] * jobnr) / nb_jobs;
> > +            const int slice_end = (s->planeheight[plane] * (jobnr+1)) / nb_jobs;
> > +            const int slice_offset = slice_start * frame->linesize[plane];
> > +            const uint16_t *p = (const uint16_t *) (frame->data[plane] + slice_offset);
> > +            const ptrdiff_t linesize = frame->linesize[plane] >> 1;
> > +            const int planewidth = s->planewidth[plane];
> > +            const int shift = s->bitdepth - 8;
> > +            int *hhist = hist + 256 * plane;
> > +
> > +            for (int j = slice_start; j < slice_end; j++) {
> > +                for (int i = 0; i < planewidth; i++)
> > +                    hhist[(p[i] >> shift) & 0xFF]++;
> > +                p += linesize;
> > +            }
> > +        }
> > +        break;
> >      }
> >
> >      return 0;
> > @@ -286,6 +322,7 @@ static int config_props(AVFilterLink *inlink)
> >      s->planewidth[0]  = s->planewidth[3]  = inlink->w;
> >      s->planeheight[1] = s->planeheight[2] = AV_CEIL_RSHIFT(inlink->h, desc->log2_chroma_h);
> >      s->planeheight[0] = s->planeheight[3] = inlink->h;
> > +    s->bitdepth       = desc->comp[0].depth;
> >
> >      return 0;
> >  }
> > @@ -304,6 +341,21 @@ static const enum AVPixelFormat pix_fmts[] = {
> >      AV_PIX_FMT_YUVJ411P,
> >      AV_PIX_FMT_YUVA420P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA444P,
> >      AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP,
> > +
> > +    /* High bit depth formats */
> > +    AV_PIX_FMT_YUV420P9,  AV_PIX_FMT_YUV422P9,  AV_PIX_FMT_YUV444P9,
> > +    AV_PIX_FMT_YUV420P10, AV_PIX_FMT_YUV422P10, AV_PIX_FMT_YUV444P10,
> > +    AV_PIX_FMT_YUV420P12, AV_PIX_FMT_YUV422P12, AV_PIX_FMT_YUV444P12,
> > +    AV_PIX_FMT_YUV420P14, AV_PIX_FMT_YUV422P14, AV_PIX_FMT_YUV444P14,
> > +    AV_PIX_FMT_YUV420P16, AV_PIX_FMT_YUV422P16, AV_PIX_FMT_YUV444P16,
> > +    AV_PIX_FMT_YUVA420P9,  AV_PIX_FMT_YUVA422P9,  AV_PIX_FMT_YUVA444P9,
> > +    AV_PIX_FMT_YUVA420P10, AV_PIX_FMT_YUVA422P10, AV_PIX_FMT_YUVA444P10,
> > +                           AV_PIX_FMT_YUVA422P12, AV_PIX_FMT_YUVA444P12,
> > +    AV_PIX_FMT_YUVA420P16, AV_PIX_FMT_YUVA422P16, AV_PIX_FMT_YUVA444P16,
> > +    AV_PIX_FMT_GBRP9,  AV_PIX_FMT_GBRP10, AV_PIX_FMT_GBRP12,
> > +    AV_PIX_FMT_GBRAP12, AV_PIX_FMT_GBRP14, AV_PIX_FMT_GBRAP14,
> > +    AV_PIX_FMT_GBRP16, AV_PIX_FMT_GBRAP16,
> > +
> >      AV_PIX_FMT_NONE
> >  };
> >
>
> Can't you use some AVPixFmtDescriptor magic to replace this huge list
> with a query formats function?

Sure. I will submit that as a separate commit, I think.

>
> - Andreas
>
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