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Tune HistogramCombineBin for large images.

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Tune HistogramCombineBin for hard images that are larger than 1-2 Mega
pixel and represent photographic images.

This speeds up lossless encoding on 1000 image corpus by 10-12% and compression
penalty of 0.1-0.2%.

Change-Id: Ifd03b75c503b9e886098e5fe6f86be0391ca8e81
This commit is contained in:
Vikas Arora 2014-03-28 07:06:54 -07:00
parent af93bdd6bc
commit 6af6b8e1b6
1 changed files with 16 additions and 4 deletions
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20
src/enc/histogram.c
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@ -561,8 +561,8 @@ static void HistogramCompactBins(VP8LHistogramSet* const histo_image) {
}
static void HistogramCombineBin(VP8LHistogramSet* const histo_image,
VP8LHistogram* const histos,
int bin_depth,
VP8LHistogram* const histos, int bin_depth,
double combine_cost_factor,
int16_t* const bin_map) {
int bin_id;
VP8LHistogram* cur_combo = histos;
@ -576,7 +576,7 @@ static void HistogramCombineBin(VP8LHistogramSet* const histo_image,
const int idx2 = bin_map[bin_offset + n];
const double bit_cost_idx2 = histo_image->histograms[idx2]->bit_cost_;
if (bit_cost_idx2 > 0.) {
const double bit_cost_thresh = -bit_cost_idx2 * 0.1;
const double bit_cost_thresh = -bit_cost_idx2 * combine_cost_factor;
const double curr_cost_diff =
HistogramAddEval(histo_image->histograms[idx1],
histo_image->histograms[idx2],
@ -706,6 +706,15 @@ static void HistogramRemap(const VP8LHistogramSet* const init_histo,
}
}
static double GetCombineCostFactor(int histo_size, int quality) {
double combine_cost_factor = 0.16;
if (histo_size > 256) combine_cost_factor /= 2.;
if (histo_size > 512) combine_cost_factor /= 2.;
if (histo_size > 1024) combine_cost_factor /= 2.;
if (quality <= 50) combine_cost_factor /= 2.;
return combine_cost_factor;
}
int VP8LGetHistoImageSymbols(int xsize, int ysize,
const VP8LBackwardRefs* const refs,
int quality, int histo_bits, int cache_bits,
@ -746,8 +755,11 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize,
HistogramBuild(xsize, histo_bits, refs, init_histo);
if (bin_map != NULL) {
const double combine_cost_factor =
GetCombineCostFactor(histo_image_raw_size, quality);
HistogramAnalyzeBin(init_histo, histo_image, bin_map);
HistogramCombineBin(histo_image, histos, bin_depth, bin_map);
HistogramCombineBin(histo_image, histos, bin_depth, combine_cost_factor,
bin_map);
} else {
HistogramAnalyze(init_histo, histo_image);
}