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Speedups for empty histograms.

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When histograms are empty, it is easy to add them.
They should also not be considered when merging histograms
(it is a waste of CPU).
This does not change the compression performance,
just the speed.

Change-Id: I42c721ca0f9c5ea067e73b792aa3db6d5e71d01f
This commit is contained in:
Vincent Rabaud
2018-09-28 15:32:25 +02:00
parent dea3e89983
commit decf6f6b87
3 changed files with 116 additions and 46 deletions
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3
src/enc/histogram_enc.h
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@ -44,6 +44,7 @@ typedef struct {
double literal_cost_; // Cached values of dominant entropy costs:
double red_cost_; // literal, red & blue.
double blue_cost_;
uint8_t is_used_[5]; // 5 for literal, red, blue, alpha, distance
} VP8LHistogram;
// Collection of histograms with fixed capacity, allocated as one
@ -113,7 +114,7 @@ double VP8LBitsEntropy(const uint32_t* const array, int n);
// Estimate how many bits the combined entropy of literals and distance
// approximately maps to.
double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
double VP8LHistogramEstimateBits(VP8LHistogram* const p);
#ifdef __cplusplus
}