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Updated VP8LGetBackwardReferences and color cache.

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- The optimal cache bits is evaluated inside the method 'VP8LGetBackwardReferences'.
- The input cache_bits to 'VP8LGetBackwardReferences' sets the maximum cache
  bits to use (passing 0 implies disabling the local color cache).
- The local color cache is disabled for lowerf (<= 25) quality levels (as before).
- Enabled local color cache for palette images as well. This saves additional
  0.017% bytes with a slight (2-3%) improvement in the compression speed.
- Removed 'use_2d_locality' parameter from method VP8LGetBackwardReferences, as
  this option is not an option now (after we freeze the lossless bit-stream).

Change-Id: I33430401e465474fa1be899f330387cd2b466280
This commit is contained in:
Vikas Arora
2014-11-06 13:13:00 -08:00
parent aa42f4231f
commit 95a9bd85c4
3 changed files with 74 additions and 66 deletions
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59
src/enc/backward_references.c
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@ -810,32 +810,48 @@ static void BackwardReferences2DLocality(int xsize,
}
}
static int CalculateBestCacheSize(const uint32_t* const argb,
int xsize, int ysize, int quality,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs* const refs,
int* const best_cache_bits);
VP8LBackwardRefs* VP8LGetBackwardReferences(
int width, int height, const uint32_t* const argb, int quality,
int cache_bits, int use_2d_locality, VP8LHashChain* const hash_chain,
int* cache_bits, VP8LHashChain* const hash_chain,
VP8LBackwardRefs refs_array[2]) {
int lz77_is_useful;
double bit_cost_lz77, bit_cost_rle;
VP8LBackwardRefs* best = NULL;
VP8LBackwardRefs* const refs_lz77 = &refs_array[0];
VP8LBackwardRefs* const refs_rle = &refs_array[1];
VP8LHistogram* const histo = VP8LAllocateHistogram(cache_bits);
if (histo == NULL) return NULL;
VP8LHistogram* histo = NULL;
if (!BackwardReferencesLz77(width, height, argb, cache_bits, quality,
if (!CalculateBestCacheSize(argb, width, height, quality, hash_chain,
refs_lz77, cache_bits)) {
goto Error;
}
// TODO(vikasa): Use the refs_lz77 computed (with cache_bits=0) in the method
// 'CalculateBestCacheSize' to regenerate the lz77 references corresponding to
// the optimum cache_bits and avoid calling 'BackwardReferencesLz77' here.
if (!BackwardReferencesLz77(width, height, argb, *cache_bits, quality,
hash_chain, refs_lz77)) {
goto Error;
}
if (!BackwardReferencesRle(width, height, argb, cache_bits, refs_rle)) {
if (!BackwardReferencesRle(width, height, argb, *cache_bits, refs_rle)) {
goto Error;
}
histo = VP8LAllocateHistogram(*cache_bits);
if (histo == NULL) goto Error;
{
// Evaluate LZ77 coding.
VP8LHistogramCreate(histo, refs_lz77, cache_bits);
VP8LHistogramCreate(histo, refs_lz77, *cache_bits);
bit_cost_lz77 = VP8LHistogramEstimateBits(histo);
// Evaluate RLE coding.
VP8LHistogramCreate(histo, refs_rle, cache_bits);
VP8LHistogramCreate(histo, refs_rle, *cache_bits);
bit_cost_rle = VP8LHistogramEstimateBits(histo);
// Decide if LZ77 is useful.
lz77_is_useful = (bit_cost_lz77 < bit_cost_rle);
@ -853,11 +869,11 @@ VP8LBackwardRefs* VP8LGetBackwardReferences(
goto Error;
}
if (BackwardReferencesTraceBackwards(width, height, argb, quality,
cache_bits, hash_chain,
*cache_bits, hash_chain,
refs_trace)) {
double bit_cost_trace;
// Evaluate LZ77 coding.
VP8LHistogramCreate(histo, refs_trace, cache_bits);
VP8LHistogramCreate(histo, refs_trace, *cache_bits);
bit_cost_trace = VP8LHistogramEstimateBits(histo);
if (bit_cost_trace < bit_cost_lz77) {
best = refs_trace;
@ -868,7 +884,7 @@ VP8LBackwardRefs* VP8LGetBackwardReferences(
best = refs_rle;
}
if (use_2d_locality) BackwardReferences2DLocality(width, best);
BackwardReferences2DLocality(width, best);
Error:
VP8LFreeHistogram(histo);
@ -930,30 +946,33 @@ static double ComputeCacheEntropy(const uint32_t* const argb,
return entropy;
}
// *best_cache_bits will contain how many bits are to be used for a color cache.
// Evaluate optimal cache bits for the local color cache.
// The input *best_cache_bits sets the maximum cache bits to use (passing 0
// implies disabling the local color cache). The local color cache is also
// disabled for the lower (<= 25) quality.
// Returns 0 in case of memory error.
int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb,
int xsize, int ysize, int quality,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs* const refs,
int* const best_cache_bits) {
static int CalculateBestCacheSize(const uint32_t* const argb,
int xsize, int ysize, int quality,
VP8LHashChain* const hash_chain,
VP8LBackwardRefs* const refs,
int* const best_cache_bits) {
int eval_low = 1;
int eval_high = 1;
double entropy_low = MAX_ENTROPY;
double entropy_high = MAX_ENTROPY;
const double cost_mul = 5e-4;
int cache_bits_low = 0;
int cache_bits_high = *best_cache_bits;
int cache_bits_high = (quality <= 25) ? 0 : *best_cache_bits;
assert(cache_bits_high <= MAX_COLOR_CACHE_BITS);
if (cache_bits_high == 0) {
*best_cache_bits = 0;
// Local color cache is disabled.
return 1;
}
if (!BackwardReferencesLz77(xsize, ysize, argb, 0, quality, hash_chain,
refs)) {
if (!BackwardReferencesLz77(xsize, ysize, argb, cache_bits_low, quality,
hash_chain, refs)) {
return 0;
}
// Do a binary search to find the optimal entropy for cache_bits.