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avfilter/palettegen: use lowbias32 for color hashing

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1.12x faster overall in palettegen on my machine.
This commit is contained in:
Clément Bœsch
2022-12-27 17:38:57 +01:00
parent 3cafbdc083
commit c9084cd0e2
1 changed files with 2 additions and 17 deletions
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19
libavfilter/vf_palettegen.c
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@@ -63,8 +63,7 @@ enum {
NB_STATS_MODE NB_STATS_MODE
}; };
#define NBITS 5 #define HIST_SIZE (1<<15)
#define HIST_SIZE (1<<(3*NBITS))
typedef struct PaletteGenContext { typedef struct PaletteGenContext {
const AVClass *class; const AVClass *class;
@@ -387,27 +386,13 @@ static AVFrame *get_palette_frame(AVFilterContext *ctx)
return out; return out;
} }
/**
* Hashing function for the color.
* It keeps the NBITS least significant bit of each component to make it
* "random" even if the scene doesn't have much different colors.
*/
static inline unsigned color_hash(uint32_t color)
{
const uint8_t r = color >> 16 & ((1<<NBITS)-1);
const uint8_t g = color >> 8 & ((1<<NBITS)-1);
const uint8_t b = color & ((1<<NBITS)-1);
return r << (NBITS * 2) | g << NBITS | b;
}
/** /**
* Locate the color in the hash table and increment its counter. * Locate the color in the hash table and increment its counter.
*/ */
static int color_inc(struct hist_node *hist, uint32_t color) static int color_inc(struct hist_node *hist, uint32_t color)
{ {
int i; int i;
const unsigned hash = color_hash(color); const uint32_t hash = ff_lowbias32(color) & (HIST_SIZE - 1);
struct hist_node *node = &hist[hash]; struct hist_node *node = &hist[hash];
struct color_ref *e; struct color_ref *e;