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Speed up HistogramCombine for lower qualities.

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Make the heuristic for combining Histograms a function of compression
quality. This change will speed-up compression time for compression
quality less than 75. The compression time/density remains unchanged
for compression quality 75 and higher.

Change-Id: I94513d51078340fbc0737d459fab2cebdd2d6082
This commit is contained in:
Vikas Arora 2012-10-16 15:42:15 -07:00
parent 1765cb1ca5
commit c3aa215afa
1 changed files with 13 additions and 6 deletions
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19
src/enc/histogram.c
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@ -249,14 +249,15 @@ static uint32_t MyRand(uint32_t *seed) {
}
static int HistogramCombine(const VP8LHistogramSet* const in,
VP8LHistogramSet* const out, int num_pairs) {
VP8LHistogramSet* const out,
int min_cluster_size, int iter_mult,
int num_pairs, int num_tries_no_success) {
int ok = 0;
int i, iter;
uint32_t seed = 0;
int tries_with_no_success = 0;
const int min_cluster_size = 2;
int out_size = in->size;
const int outer_iters = in->size * 3;
const int outer_iters = in->size * iter_mult;
VP8LHistogram* const histos = (VP8LHistogram*)malloc(2 * sizeof(*histos));
VP8LHistogram* cur_combo = histos + 0; // trial merged histogram
VP8LHistogram* best_combo = histos + 1; // best merged histogram so far
@ -315,7 +316,7 @@ static int HistogramCombine(const VP8LHistogramSet* const in,
}
tries_with_no_success = 0;
}
if (++tries_with_no_success >= 50) {
if (++tries_with_no_success >= num_tries_no_success) {
break;
}
}
@ -384,8 +385,13 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize,
int ok = 0;
const int histo_xsize = histo_bits ? VP8LSubSampleSize(xsize, histo_bits) : 1;
const int histo_ysize = histo_bits ? VP8LSubSampleSize(ysize, histo_bits) : 1;
const int num_histo_pairs = 10 + quality / 2; // For HistogramCombine().
const int histo_image_raw_size = histo_xsize * histo_ysize;
// Heuristic params for HistogramCombine().
const int num_pairs = 8 + (quality >> 1);
const int num_tries_no_success = 8 + (quality >> 1);
const int min_cluster_size = (quality >= 25) ? ((quality >= 75) ? 2 : 3) : 4;
const int iter_mult = (quality >= 25) ? ((quality >= 75) ? 3 : 2) : 1;
VP8LHistogramSet* const image_out =
VP8LAllocateHistogramSet(histo_image_raw_size, cache_bits);
if (image_out == NULL) return 0;
@ -393,7 +399,8 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize,
// Build histogram image.
HistogramBuildImage(xsize, histo_bits, refs, image_out);
// Collapse similar histograms.
if (!HistogramCombine(image_out, image_in, num_histo_pairs)) {
if (!HistogramCombine(image_out, image_in, min_cluster_size, iter_mult,
num_pairs, num_tries_no_success)) {
goto Error;
}
// Find the optimal map from original histograms to the final ones.