From 30d43706d30262f72812f4f56d70db3f83e35c33 Mon Sep 17 00:00:00 2001 From: Vincent Rabaud Date: Wed, 28 Sep 2016 13:22:13 +0200 Subject: [PATCH] Speed-up Combined entropy for palettized histograms. Change-Id: Ie9bdebb26c726e5b44c2dbcc84d453f85a03f419 --- src/enc/histogram.c | 71 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 56 insertions(+), 15 deletions(-) diff --git a/src/enc/histogram.c b/src/enc/histogram.c index b2811ecb..a52520b0 100644 --- a/src/enc/histogram.c +++ b/src/enc/histogram.c @@ -237,14 +237,30 @@ static double PopulationCost(const uint32_t* const population, int length, return BitsEntropyRefine(&bit_entropy) + FinalHuffmanCost(&stats); } +// trivial_at_end is 1 if the two histograms only have one element that is +// non-zero: both the zero-th one, or both the last one. static WEBP_INLINE double GetCombinedEntropy(const uint32_t* const X, const uint32_t* const Y, - int length) { - VP8LBitEntropy bit_entropy; + int length, int trivial_at_end) { VP8LStreaks stats; - VP8LGetCombinedEntropyUnrefined(X, Y, length, &bit_entropy, &stats); + if (trivial_at_end) { + // This configuration is due to palettization that transforms an indexed + // pixel into 0xff000000 | (pixel << 8) in VP8LBundleColorMap. + // BitsEntropyRefine is 0 for histograms with only one non-zero value. + // Only FinalHuffmanCost needs to be evaluated. + memset(&stats, 0, sizeof(stats)); + // Deal with the non-zero value at index 0 or length-1. + stats.streaks[1][0] += 1; + // Deal with the following/previous zero streak. + stats.counts[0] += 1; + stats.streaks[0][1] += length - 1; + return FinalHuffmanCost(&stats); + } else { + VP8LBitEntropy bit_entropy; + VP8LGetCombinedEntropyUnrefined(X, Y, length, &bit_entropy, &stats); - return BitsEntropyRefine(&bit_entropy) + FinalHuffmanCost(&stats); + return BitsEntropyRefine(&bit_entropy) + FinalHuffmanCost(&stats); + } } // Estimates the Entropy + Huffman + other block overhead size cost. @@ -268,24 +284,42 @@ static int GetCombinedHistogramEntropy(const VP8LHistogram* const a, double cost_threshold, double* cost) { const int palette_code_bits = a->palette_code_bits_; + int trivial_at_end = 0; assert(a->palette_code_bits_ == b->palette_code_bits_); *cost += GetCombinedEntropy(a->literal_, b->literal_, - VP8LHistogramNumCodes(palette_code_bits)); + VP8LHistogramNumCodes(palette_code_bits), 0); *cost += VP8LExtraCostCombined(a->literal_ + NUM_LITERAL_CODES, b->literal_ + NUM_LITERAL_CODES, NUM_LENGTH_CODES); if (*cost > cost_threshold) return 0; - *cost += GetCombinedEntropy(a->red_, b->red_, NUM_LITERAL_CODES); + if (a->trivial_symbol_ != VP8L_NON_TRIVIAL_SYM && + a->trivial_symbol_ == b->trivial_symbol_) { + // A, R and B are all 0 or 0xff. + const uint32_t color_a = (a->trivial_symbol_ >> 24) & 0xff; + const uint32_t color_r = (a->trivial_symbol_ >> 16) & 0xff; + const uint32_t color_b = (a->trivial_symbol_ >> 0) & 0xff; + if ((color_a == 0 || color_a == 0xff) && + (color_r == 0 || color_r == 0xff) && + (color_b == 0 || color_b == 0xff)) { + trivial_at_end = 1; + } + } + + *cost += + GetCombinedEntropy(a->red_, b->red_, NUM_LITERAL_CODES, trivial_at_end); if (*cost > cost_threshold) return 0; - *cost += GetCombinedEntropy(a->blue_, b->blue_, NUM_LITERAL_CODES); + *cost += + GetCombinedEntropy(a->blue_, b->blue_, NUM_LITERAL_CODES, trivial_at_end); if (*cost > cost_threshold) return 0; - *cost += GetCombinedEntropy(a->alpha_, b->alpha_, NUM_LITERAL_CODES); + *cost += GetCombinedEntropy(a->alpha_, b->alpha_, NUM_LITERAL_CODES, + trivial_at_end); if (*cost > cost_threshold) return 0; - *cost += GetCombinedEntropy(a->distance_, b->distance_, NUM_DISTANCE_CODES); + *cost += + GetCombinedEntropy(a->distance_, b->distance_, NUM_DISTANCE_CODES, 0); *cost += VP8LExtraCostCombined(a->distance_, b->distance_, NUM_DISTANCE_CODES); if (*cost > cost_threshold) return 0; @@ -293,6 +327,15 @@ static int GetCombinedHistogramEntropy(const VP8LHistogram* const a, return 1; } +static WEBP_INLINE void HistogramAdd(const VP8LHistogram* const a, + const VP8LHistogram* const b, + VP8LHistogram* const out) { + VP8LHistogramAdd(a, b, out); + out->trivial_symbol_ = (a->trivial_symbol_ == b->trivial_symbol_) + ? a->trivial_symbol_ + : VP8L_NON_TRIVIAL_SYM; +} + // Performs out = a + b, computing the cost C(a+b) - C(a) - C(b) while comparing // to the threshold value 'cost_threshold'. The score returned is // Score = C(a+b) - C(a) - C(b), where C(a) + C(b) is known and fixed. @@ -308,11 +351,9 @@ static double HistogramAddEval(const VP8LHistogram* const a, cost_threshold += sum_cost; if (GetCombinedHistogramEntropy(a, b, cost_threshold, &cost)) { - VP8LHistogramAdd(a, b, out); + HistogramAdd(a, b, out); out->bit_cost_ = cost; out->palette_code_bits_ = a->palette_code_bits_; - out->trivial_symbol_ = (a->trivial_symbol_ == b->trivial_symbol_) ? - a->trivial_symbol_ : VP8L_NON_TRIVIAL_SYM; } return cost - sum_cost; @@ -504,7 +545,7 @@ static VP8LHistogram* HistogramCombineEntropyBin( histograms[size] = histograms[idx]; bin_info[bin_id].first = size++; } else if (low_effort) { - VP8LHistogramAdd(histograms[idx], histograms[first], histograms[first]); + HistogramAdd(histograms[idx], histograms[first], histograms[first]); } else { // try to merge #idx into #first (both share the same bin_id) const double bit_cost = histograms[idx]->bit_cost_; @@ -672,7 +713,7 @@ static int HistogramCombineGreedy(VP8LHistogramSet* const image_histo) { HistogramPair* copy_to; const int idx1 = histo_queue.queue[0].idx1; const int idx2 = histo_queue.queue[0].idx2; - VP8LHistogramAdd(histograms[idx2], histograms[idx1], histograms[idx1]); + HistogramAdd(histograms[idx2], histograms[idx1], histograms[idx1]); histograms[idx1]->bit_cost_ = histo_queue.queue[0].cost_combo; // Remove merged histogram. for (i = 0; i + 1 < image_histo_size; ++i) { @@ -854,7 +895,7 @@ static void HistogramRemap(const VP8LHistogramSet* const in, for (i = 0; i < in_size; ++i) { const int idx = symbols[i]; - VP8LHistogramAdd(in_histo[i], out_histo[idx], out_histo[idx]); + HistogramAdd(in_histo[i], out_histo[idx], out_histo[idx]); } }