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Fix bug in VP8LCalculateEstimateForCacheSize.

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The method VP8LCalculateEstimateForCacheSize is not evaluating the all possible
range for cache_bits.
Also added a small penality for choosing the larger cache-size. This is done to
strike a balance between additional memory/CPU cost (with larger cache-size) and
byte savings from smaller WebP lossless files.

This change saves about 0.07% bytes and speeds up compression by 8% (default
settings). There's small speedup at Q=50 along with byte savings as well.
Compression at Quality=25 is not effected by this change.

Change-Id: Id8f87dee6b5bccb2baa6dbdee479ee9cda8f4f77
This commit is contained in:
Vikas Arora
2014-10-23 09:01:46 -07:00
parent 613d281e87
commit e912bd55be
2 changed files with 21 additions and 12 deletions
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14
src/enc/vp8l.c
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@ -284,7 +284,7 @@ static int GetTransformBits(int method, int histo_bits) {
static int GetCacheBits(int use_palette, float quality) {
// Color cache is disabled for compression at lower quality or when a palette
// is used.
return (use_palette || (quality <= 25.f)) ? 0 : 7;
return (use_palette || (quality <= 25.f)) ? 0 : MAX_COLOR_CACHE_BITS;
}
static int EvalSubtractGreenForPalette(int palette_size, float quality) {
@ -1309,13 +1309,11 @@ WebPEncodingError VP8LEncodeStream(const WebPConfig* const config,
// ---------------------------------------------------------------------------
// Estimate the color cache size.
if (enc->cache_bits_ > 0) {
if (!VP8LCalculateEstimateForCacheSize(enc->argb_, enc->current_width_,
height, quality, &enc->hash_chain_,
&enc->refs_[0], &enc->cache_bits_)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
if (!VP8LCalculateEstimateForCacheSize(enc->argb_, enc->current_width_,
height, quality, &enc->hash_chain_,
&enc->refs_[0], &enc->cache_bits_)) {
err = VP8_ENC_ERROR_OUT_OF_MEMORY;
goto Error;
}
// ---------------------------------------------------------------------------