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lossless: ~20 % speedup

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0.28 % byte size increase on lossless, 0.18 % increase on lossy alpha

Change-Id: I1e001a56831a8f996ac522aa646f9ae587c80d12
This commit is contained in:
Jyrki Alakuijala 2015-07-03 15:09:40 +00:00 committed by James Zern
parent f722c8f0bd
commit 01d61fd9c6
1 changed files with 17 additions and 29 deletions
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46
src/enc/backward_references.c
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@ -232,14 +232,10 @@ static void HashChainInsert(VP8LHashChain* const p,
p->hash_to_first_index_[hash_code] = pos; p->hash_to_first_index_[hash_code] = pos;
} }
static void GetParamsForHashChainFindCopy( // Returns the maximum number of hash chain lookups to do for a
int quality, int low_effort, int* iter_max, int* len_for_unit_dist) { // given compression quality. Return value in range [6, 86].
*iter_max = 8 + (quality * quality) / 40; static int GetMaxItersForQuality(int quality, int low_effort) {
*len_for_unit_dist = 32 + (96 * quality) / 100; return (low_effort ? 6 : 8) + (quality * quality) / 128;
if (low_effort) {
*iter_max -= 2;
*len_for_unit_dist /= 4;
}
} }
static int GetWindowSizeForHashChain(int quality, int xsize) { static int GetWindowSizeForHashChain(int quality, int xsize) {
@ -274,15 +270,14 @@ static void HashChainFindOffset(const VP8LHashChain* const p, int base_position,
} }
static int HashChainFindCopy(const VP8LHashChain* const p, static int HashChainFindCopy(const VP8LHashChain* const p,
int base_position, int xsize, int base_position,
const uint32_t* const argb, int max_len, const uint32_t* const argb, int max_len,
int window_size, int iter_max, int window_size, int iter_max,
int len_for_unit_dist,
int* const distance_ptr, int* const distance_ptr,
int* const length_ptr) { int* const length_ptr) {
const uint32_t* const argb_start = argb + base_position; const uint32_t* const argb_start = argb + base_position;
int iter = iter_max; int iter = iter_max;
int best_length = 1; int best_length = 0;
int best_distance = 0; int best_distance = 0;
const int min_pos = const int min_pos =
(base_position > window_size) ? base_position - window_size : 0; (base_position > window_size) ? base_position - window_size : 0;
@ -291,7 +286,6 @@ static int HashChainFindCopy(const VP8LHashChain* const p,
if (max_len < length_max) { if (max_len < length_max) {
length_max = max_len; length_max = max_len;
} }
assert(xsize > 0);
for (pos = p->hash_to_first_index_[GetPixPairHash64(argb_start)]; for (pos = p->hash_to_first_index_[GetPixPairHash64(argb_start)];
pos >= min_pos; pos >= min_pos;
pos = p->chain_[pos]) { pos = p->chain_[pos]) {
@ -309,10 +303,6 @@ static int HashChainFindCopy(const VP8LHashChain* const p,
if (curr_length >= length_max) { if (curr_length >= length_max) {
break; break;
} }
if ((distance == 1 || distance == xsize) &&
best_length >= len_for_unit_dist) {
break;
}
} }
} }
*distance_ptr = best_distance; *distance_ptr = best_distance;
@ -390,11 +380,9 @@ static int BackwardReferencesLz77(int xsize, int ysize,
const int use_color_cache = (cache_bits > 0); const int use_color_cache = (cache_bits > 0);
const int pix_count = xsize * ysize; const int pix_count = xsize * ysize;
VP8LColorCache hashers; VP8LColorCache hashers;
int iter_max, len_for_unit_dist; int iter_max = GetMaxItersForQuality(quality, low_effort);
const int window_size = GetWindowSizeForHashChain(quality, xsize); const int window_size = GetWindowSizeForHashChain(quality, xsize);
int min_matches = 32; int min_matches = 32;
GetParamsForHashChainFindCopy(quality, low_effort, &iter_max,
&len_for_unit_dist);
if (use_color_cache) { if (use_color_cache) {
cc_init = VP8LColorCacheInit(&hashers, cache_bits); cc_init = VP8LColorCacheInit(&hashers, cache_bits);
@ -407,8 +395,8 @@ static int BackwardReferencesLz77(int xsize, int ysize,
int offset = 0; int offset = 0;
int len = 0; int len = 0;
const int max_len = MaxFindCopyLength(pix_count - i); const int max_len = MaxFindCopyLength(pix_count - i);
HashChainFindCopy(hash_chain, i, xsize, argb, max_len, window_size, HashChainFindCopy(hash_chain, i, argb, max_len, window_size,
iter_max, len_for_unit_dist, &offset, &len); iter_max, &offset, &len);
if (len > MIN_LENGTH || (len == MIN_LENGTH && offset <= 512)) { if (len > MIN_LENGTH || (len == MIN_LENGTH && offset <= 512)) {
int offset2 = 0; int offset2 = 0;
int len2 = 0; int len2 = 0;
@ -418,8 +406,8 @@ static int BackwardReferencesLz77(int xsize, int ysize,
if ((len < (max_len >> 2)) && !low_effort) { if ((len < (max_len >> 2)) && !low_effort) {
// Evaluate Alternative#2: Insert the pixel at 'i' as literal, and code // Evaluate Alternative#2: Insert the pixel at 'i' as literal, and code
// the pixels starting at 'i + 1' using backward reference. // the pixels starting at 'i + 1' using backward reference.
HashChainFindCopy(hash_chain, i + 1, xsize, argb, max_len - 1, HashChainFindCopy(hash_chain, i + 1, argb, max_len - 1,
window_size, iter_max, len_for_unit_dist, &offset2, window_size, iter_max, &offset2,
&len2); &len2);
if (len2 > len + 1) { if (len2 > len + 1) {
AddSingleLiteral(argb[i], use_color_cache, &hashers, refs); AddSingleLiteral(argb[i], use_color_cache, &hashers, refs);
@ -597,10 +585,10 @@ static int BackwardReferencesHashChainDistanceOnly(
CostModel* const cost_model = CostModel* const cost_model =
(CostModel*)WebPSafeMalloc(1ULL, cost_model_size); (CostModel*)WebPSafeMalloc(1ULL, cost_model_size);
VP8LColorCache hashers; VP8LColorCache hashers;
const int min_distance_code = 2; const int skip_length = 32 + quality;
int iter_max, len_for_unit_dist; const int skip_min_distance_code = 2;
int iter_max = GetMaxItersForQuality(quality, 0);
const int window_size = GetWindowSizeForHashChain(quality, xsize); const int window_size = GetWindowSizeForHashChain(quality, xsize);
GetParamsForHashChainFindCopy(quality, 0, &iter_max, &len_for_unit_dist);
if (cost == NULL || cost_model == NULL) goto Error; if (cost == NULL || cost_model == NULL) goto Error;
@ -628,8 +616,8 @@ static int BackwardReferencesHashChainDistanceOnly(
int len = 0; int len = 0;
double prev_cost = cost[i - 1]; double prev_cost = cost[i - 1];
const int max_len = MaxFindCopyLength(pix_count - i); const int max_len = MaxFindCopyLength(pix_count - i);
HashChainFindCopy(hash_chain, i, xsize, argb, max_len, window_size, HashChainFindCopy(hash_chain, i, argb, max_len, window_size,
iter_max, len_for_unit_dist, &offset, &len); iter_max, &offset, &len);
if (len >= MIN_LENGTH) { if (len >= MIN_LENGTH) {
const int code = DistanceToPlaneCode(xsize, offset); const int code = DistanceToPlaneCode(xsize, offset);
const double distance_cost = const double distance_cost =
@ -644,7 +632,7 @@ static int BackwardReferencesHashChainDistanceOnly(
} }
// This if is for speedup only. It roughly doubles the speed, and // This if is for speedup only. It roughly doubles the speed, and
// makes compression worse by .1 %. // makes compression worse by .1 %.
if (len >= len_for_unit_dist && code <= min_distance_code) { if (len >= skip_length && code <= skip_min_distance_code) {
// Long copy for short distances, let's skip the middle // Long copy for short distances, let's skip the middle
// lookups for better copies. // lookups for better copies.
// 1) insert the hashes. // 1) insert the hashes.