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Tune performance of HistogramCombine

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Number of pairs selected are limited between 25% of histogram
images (at start) and number of histogram images left at any iteration.
Increase the range of iter_mult.
Removed min_cluster_size as parameter for tuning HistogramCombine.

Change-Id: Ia4068cd7af4d0f63c5af9001aceda8a40b9de740
This commit is contained in:
vikas arora 2012-11-05 16:44:19 -08:00
parent 52ad1979d2
commit 812933d6ba
1 changed files with 14 additions and 9 deletions
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23
src/enc/histogram.c
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@ -249,8 +249,7 @@ static uint32_t MyRand(uint32_t *seed) {
}
static int HistogramCombine(const VP8LHistogramSet* const in,
VP8LHistogramSet* const out,
int min_cluster_size, int iter_mult,
VP8LHistogramSet* const out, int iter_mult,
int num_pairs, int num_tries_no_success) {
int ok = 0;
int i, iter;
@ -258,6 +257,7 @@ static int HistogramCombine(const VP8LHistogramSet* const in,
int tries_with_no_success = 0;
int out_size = in->size;
const int outer_iters = in->size * iter_mult;
const int min_cluster_size = 2;
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
@ -272,12 +272,12 @@ static int HistogramCombine(const VP8LHistogramSet* const in,
// Collapse similar histograms in 'out'.
for (iter = 0; iter < outer_iters && out_size >= min_cluster_size; ++iter) {
// We pick the best pair to be combined out of 'inner_iters' pairs.
double best_cost_diff = 0.;
int best_idx1 = 0, best_idx2 = 1;
int j;
const int num_tries = (num_pairs < out_size) ? num_pairs : out_size;
seed += iter;
for (j = 0; j < num_pairs; ++j) {
for (j = 0; j < num_tries; ++j) {
double curr_cost_diff;
// Choose two histograms at random and try to combine them.
const uint32_t idx1 = MyRand(&seed) % out_size;
@ -386,21 +386,26 @@ int VP8LGetHistoImageSymbols(int xsize, int ysize,
const int histo_xsize = histo_bits ? VP8LSubSampleSize(xsize, histo_bits) : 1;
const int histo_ysize = histo_bits ? VP8LSubSampleSize(ysize, histo_bits) : 1;
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;
const int iter_mult = (quality < 27) ? 1 : 1 + ((quality - 27) >> 4);
int num_pairs = (quality >> 1);
VP8LHistogramSet* const image_out =
VP8LAllocateHistogramSet(histo_image_raw_size, cache_bits);
if (image_out == NULL) return 0;
if (num_pairs > (histo_image_raw_size >> 2)) {
num_pairs = histo_image_raw_size >> 2;
}
num_pairs += 10;
// Build histogram image.
HistogramBuildImage(xsize, histo_bits, refs, image_out);
// Collapse similar histograms.
if (!HistogramCombine(image_out, image_in, min_cluster_size, iter_mult,
num_pairs, num_tries_no_success)) {
if (!HistogramCombine(image_out, image_in, iter_mult, num_pairs,
num_tries_no_success)) {
goto Error;
}
// Find the optimal map from original histograms to the final ones.