Re: [FFmpeg-devel] [PATCH 1/2] avfilter/vf_nlmeans: better weighting of centered pixel

[Clément Bœsch]

On Sat, May 12, 2018 at 10:24:34PM +0200, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol 
> ---
>  libavfilter/vf_nlmeans.c | 8 ++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
> index 82e779ce85..6c9c9d312d 100644
> --- a/libavfilter/vf_nlmeans.c
> +++ b/libavfilter/vf_nlmeans.c
> @@ -39,6 +39,7 @@
>  #include "video.h"
>  
>  struct weighted_avg {
> +float max_weight;
>  float total_weight;
>  float sum;
>  };
> @@ -403,6 +404,7 @@ static int nlmeans_slice(AVFilterContext *ctx, void *arg, 
> int jobnr, int nb_jobs
>  if (patch_diff_sq < s->max_meaningful_diff) {
>  const unsigned weight_lut_idx = patch_diff_sq * 
> s->pdiff_lut_scale;
>  const float weight = s->weight_lut[weight_lut_idx]; // 
> exp(-patch_diff_sq * s->pdiff_scale)
> +wa[x].max_weight = FFMAX(weight, wa[x].max_weight);
>  wa[x].total_weight += weight;
>  wa[x].sum += weight * src[x];
>  }
> @@ -422,8 +424,10 @@ static void weight_averages(uint8_t *dst, ptrdiff_t 
> dst_linesize,
>  for (y = 0; y < h; y++) {
>  for (x = 0; x < w; x++) {
>  // Also weight the centered pixel
> -wa[x].total_weight += 1.f;
> -wa[x].sum += 1.f * src[x];
> +if (!isnormal(wa[x].max_weight))
> +wa[x].max_weight = 1.f;
> +wa[x].total_weight += wa[x].max_weight;
> +wa[x].sum += src[x] * wa[x].max_weight;
>  dst[x] = av_clip_uint8(wa[x].sum / wa[x].total_weight);
>  }
>  dst += dst_linesize;

Do you mind adding a cpw/center-pixel-weight option with multiple modes?
"one" and "max" for a start would be nice, then eventually advanced modes
can be added. Please also mention https://arxiv.org/pdf/1211.1656 at least
in the commit description.

-- 
Clément B.


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[FFmpeg-devel] [PATCH 1/2] avfilter/vf_nlmeans: better weighting of centered pixel

[Paul B Mahol]

Signed-off-by: Paul B Mahol 
---
 libavfilter/vf_nlmeans.c | 8 ++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
index 82e779ce85..6c9c9d312d 100644
--- a/libavfilter/vf_nlmeans.c
+++ b/libavfilter/vf_nlmeans.c
@@ -39,6 +39,7 @@
 #include "video.h"
 
 struct weighted_avg {
+float max_weight;
 float total_weight;
 float sum;
 };
@@ -403,6 +404,7 @@ static int nlmeans_slice(AVFilterContext *ctx, void *arg, 
int jobnr, int nb_jobs
 if (patch_diff_sq < s->max_meaningful_diff) {
 const unsigned weight_lut_idx = patch_diff_sq * 
s->pdiff_lut_scale;
 const float weight = s->weight_lut[weight_lut_idx]; // 
exp(-patch_diff_sq * s->pdiff_scale)
+wa[x].max_weight = FFMAX(weight, wa[x].max_weight);
 wa[x].total_weight += weight;
 wa[x].sum += weight * src[x];
 }
@@ -422,8 +424,10 @@ static void weight_averages(uint8_t *dst, ptrdiff_t 
dst_linesize,
 for (y = 0; y < h; y++) {
 for (x = 0; x < w; x++) {
 // Also weight the centered pixel
-wa[x].total_weight += 1.f;
-wa[x].sum += 1.f * src[x];
+if (!isnormal(wa[x].max_weight))
+wa[x].max_weight = 1.f;
+wa[x].total_weight += wa[x].max_weight;
+wa[x].sum += src[x] * wa[x].max_weight;
 dst[x] = av_clip_uint8(wa[x].sum / wa[x].total_weight);
 }
 dst += dst_linesize;
-- 
2.11.0

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