Re: [FFmpeg-devel] [PATCH 7/9] lavfi/nlmeans: switch from double to float

2018-05-07 Thread Clément Bœsch 
On Sun, May 06, 2018 at 04:53:54PM +0200, Moritz Barsnick wrote:
> On Sun, May 06, 2018 at 13:40:58 +0200, Clément Bœsch wrote:
> > Overall speed appears to be 1.1x faster with no noticeable quality impact.
> 
> Probably platform dependant?
> 
> >  struct weighted_avg {
> > -double total_weight;
> > -double sum;
> > +float total_weight;
> > +float sum;
> >  };
> 
> I believe these calculaions in nlmeans_plane() will promote to double
> before being cast back to float:
> 
>// Also weight the centered pixel
> wa->total_weight += 1.0;
> wa->sum += 1.0 * src[y*src_linesize + x];
> 
> (At least the second one. The first one - just an assignment of a
> constant - is covered by the preprocessor, IIUC.) They need to use
> "1.0f".
> 

It doesn't really matter here actually, in "lavfi/nlmeans: move final
weighted averaging out of nlmeans_plane" you can see that this code
represents 0.24% of the CPU time. I fixed it locally anyway, thanks.

> (There are others, but only in init(), which don't matter for
> performance.)

Yeah, I left these to double on purpose.

-- 
Clément B.


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Re: [FFmpeg-devel] [PATCH 7/9] lavfi/nlmeans: switch from double to float

2018-05-06 Thread Moritz Barsnick 
On Sun, May 06, 2018 at 13:40:58 +0200, Clément Bœsch wrote:
> Overall speed appears to be 1.1x faster with no noticeable quality impact.

Probably platform dependant?

>  struct weighted_avg {
> -double total_weight;
> -double sum;
> +float total_weight;
> +float sum;
>  };

I believe these calculaions in nlmeans_plane() will promote to double
before being cast back to float:

   // Also weight the centered pixel
wa->total_weight += 1.0;
wa->sum += 1.0 * src[y*src_linesize + x];

(At least the second one. The first one - just an assignment of a
constant - is covered by the preprocessor, IIUC.) They need to use
"1.0f".

(There are others, but only in init(), which don't matter for
performance.)

Cheers,
Moritz
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[FFmpeg-devel] [PATCH 7/9] lavfi/nlmeans: switch from double to float

2018-05-06 Thread Clément Bœsch 
Overall speed appears to be 1.1x faster with no noticeable quality impact.
---
 libavfilter/vf_nlmeans.c | 12 ++--
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
index f37f1183f7..201e4feb41 100644
--- a/libavfilter/vf_nlmeans.c
+++ b/libavfilter/vf_nlmeans.c
@@ -40,8 +40,8 @@
 #include "video.h"
 
 struct weighted_avg {
-double total_weight;
-double sum;
+float total_weight;
+float sum;
 };
 
 #define WEIGHT_LUT_NBITS 9
@@ -63,8 +63,8 @@ typedef struct NLMeansContext {
 ptrdiff_t ii_lz_32; // linesize in 32-bit units of 
the integral image
 struct weighted_avg *wa;// weighted average of every 
pixel
 ptrdiff_t wa_linesize;  // linesize for wa in struct 
size unit
-double weight_lut[WEIGHT_LUT_SIZE]; // lookup table mapping 
(scaled) patch differences to their associated weights
-double pdiff_lut_scale; // scale factor for patch 
differences before looking into the LUT
+float weight_lut[WEIGHT_LUT_SIZE];  // lookup table mapping 
(scaled) patch differences to their associated weights
+float pdiff_lut_scale;  // scale factor for patch 
differences before looking into the LUT
 int max_meaningful_diff;// maximum difference 
considered (if the patch difference is too high we ignore the pixel)
 NLMeansDSPContext dsp;
 } NLMeansContext;
@@ -206,7 +206,7 @@ static void compute_safe_ssd_integral_image_c(uint32_t 
*dst, ptrdiff_t dst_lines
  * @param w width to compute
  * @param h height to compute
  */
-static inline void compute_unsafe_ssd_integral_image(uint32_t *dst, ptrdiff_t 
dst_linesize_32,
+static void compute_unsafe_ssd_integral_image(uint32_t *dst, ptrdiff_t 
dst_linesize_32,
  int startx, int starty,
  const uint8_t *src, 
ptrdiff_t linesize,
  int offx, int offy, int 
r, int sw, int sh,
@@ -402,7 +402,7 @@ static int nlmeans_slice(AVFilterContext *ctx, void *arg, 
int jobnr, int nb_jobs
 const int patch_diff_sq = get_integral_patch_value(td->ii_start, 
s->ii_lz_32, x, y, td->p);
 if (patch_diff_sq < s->max_meaningful_diff) {
 const int weight_lut_idx = patch_diff_sq * s->pdiff_lut_scale;
-const double weight = s->weight_lut[weight_lut_idx]; // 
exp(-patch_diff_sq * s->pdiff_scale)
+const float weight = s->weight_lut[weight_lut_idx]; // 
exp(-patch_diff_sq * s->pdiff_scale)
 wa[x].total_weight += weight;
 wa[x].sum += weight * src[x];
 }
-- 
2.17.0

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