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Refactor LZ77 handling in preparation for a new method.

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Change-Id: If305c328c8f508bd778d1af108e4eb979fbd2eca
This commit is contained in:
Vincent Rabaud
2017-06-07 15:13:35 +02:00
parent 67de68b5d9
commit a1779a017b
3 changed files with 83 additions and 57 deletions
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46
src/enc/backward_references_enc.c
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@ -688,26 +688,34 @@ extern int VP8LBackwardReferencesTraceBackwards(
const VP8LBackwardRefs* const refs_src, VP8LBackwardRefs* const refs_dst);
static VP8LBackwardRefs* GetBackwardReferences(
int width, int height, const uint32_t* const argb, int quality,
int* const cache_bits, const VP8LHashChain* const hash_chain,
VP8LBackwardRefs* best, VP8LBackwardRefs* worst) {
int lz77_types_to_try, int* const cache_bits,
const VP8LHashChain* const hash_chain, VP8LBackwardRefs* best,
VP8LBackwardRefs* worst) {
const int cache_bits_initial = *cache_bits;
double bit_cost_best = -1;
VP8LHistogram* histo = NULL;
int i, i_best = 0;
int lz77_type, lz77_type_best = 0;
histo = VP8LAllocateHistogram(MAX_COLOR_CACHE_BITS);
if (histo == NULL) goto Error;
// Try out RLE first, then LZ77.
for (i = 0; i <= 1; ++i) {
int res;
for (lz77_type = 1; lz77_types_to_try;
lz77_types_to_try &= ~lz77_type, lz77_type <<= 1) {
int res = 0;
double bit_cost;
int cache_bits_tmp = cache_bits_initial;
// First, try out backward references with no cache (0 bits).
if (i == 0) {
res = BackwardReferencesRle(width, height, argb, 0, worst);
} else {
res = BackwardReferencesLz77(width, height, argb, 0, hash_chain, worst);
if ((lz77_types_to_try & lz77_type) == 0) continue;
switch (lz77_type) {
case kLZ77RLE:
res = BackwardReferencesRle(width, height, argb, 0, worst);
break;
case kLZ77Standard:
// Compute LZ77 with no cache (0 bits), as the ideal LZ77 with a color
// cache is not that different in practice.
res = BackwardReferencesLz77(width, height, argb, 0, hash_chain, worst);
break;
default:
assert(0);
}
if (!res) goto Error;
@ -724,19 +732,20 @@ static VP8LBackwardRefs* GetBackwardReferences(
// Keep the best backward references.
VP8LHistogramCreate(histo, worst, cache_bits_tmp);
bit_cost = VP8LHistogramEstimateBits(histo);
if (i == 0 || bit_cost < bit_cost_best) {
if (lz77_type_best == 0 || bit_cost < bit_cost_best) {
VP8LBackwardRefs* const tmp = worst;
worst = best;
best = tmp;
bit_cost_best = bit_cost;
*cache_bits = cache_bits_tmp;
i_best = i;
lz77_type_best = lz77_type;
}
}
assert(lz77_type_best > 0);
// Improve on simple LZ77 but only for high quality (TraceBackwards is
// costly).
if (i_best == 1 && quality >= 25) {
if (lz77_type_best == kLZ77Standard && quality >= 25) {
if (VP8LBackwardReferencesTraceBackwards(width, height, argb, *cache_bits,
hash_chain, best, worst)) {
double bit_cost_trace;
@ -748,21 +757,22 @@ static VP8LBackwardRefs* GetBackwardReferences(
BackwardReferences2DLocality(width, best);
Error:
Error:
VP8LFreeHistogram(histo);
return best;
}
VP8LBackwardRefs* VP8LGetBackwardReferences(
int width, int height, const uint32_t* const argb, int quality,
int low_effort, int* const cache_bits,
int low_effort, int lz77_types_to_try, int* const cache_bits,
const VP8LHashChain* const hash_chain, VP8LBackwardRefs* const refs_tmp1,
VP8LBackwardRefs* const refs_tmp2) {
if (low_effort) {
return GetBackwardReferencesLowEffort(width, height, argb, cache_bits,
hash_chain, refs_tmp1);
} else {
return GetBackwardReferences(width, height, argb, quality, cache_bits,
hash_chain, refs_tmp1, refs_tmp2);
return GetBackwardReferences(width, height, argb, quality,
lz77_types_to_try, cache_bits, hash_chain,
refs_tmp1, refs_tmp2);
}
}