diff options
Diffstat (limited to 'drivers/webp/enc/backward_references.c')
| -rw-r--r-- | drivers/webp/enc/backward_references.c | 298 |
1 files changed, 139 insertions, 159 deletions
diff --git a/drivers/webp/enc/backward_references.c b/drivers/webp/enc/backward_references.c index 77b4be7432..b8c8ece806 100644 --- a/drivers/webp/enc/backward_references.c +++ b/drivers/webp/enc/backward_references.c @@ -1,10 +1,8 @@ // Copyright 2012 Google Inc. All Rights Reserved. // -// Use of this source code is governed by a BSD-style license -// that can be found in the COPYING file in the root of the source -// tree. An additional intellectual property rights grant can be found -// in the file PATENTS. All contributing project authors may -// be found in the AUTHORS file in the root of the source tree. +// This code is licensed under the same terms as WebM: +// Software License Agreement: http://www.webmproject.org/license/software/ +// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ // ----------------------------------------------------------------------------- // // Author: Jyrki Alakuijala (jyrki@google.com) @@ -143,95 +141,74 @@ static void HashChainInsert(HashChain* const p, p->hash_to_first_index_[hash_code] = pos; } -static void GetParamsForHashChainFindCopy(int quality, int xsize, - int cache_bits, int* window_size, - int* iter_pos, int* iter_limit) { - const int iter_mult = (quality < 27) ? 1 : 1 + ((quality - 27) >> 4); - const int iter_neg = -iter_mult * (quality >> 1); - // Limit the backward-ref window size for lower qualities. - const int max_window_size = (quality > 50) ? WINDOW_SIZE - : (quality > 25) ? (xsize << 8) - : (xsize << 4); - assert(xsize > 0); - *window_size = (max_window_size > WINDOW_SIZE) ? WINDOW_SIZE - : max_window_size; - *iter_pos = 8 + (quality >> 3); - // For lower entropy images, the rigorous search loop in HashChainFindCopy - // can be relaxed. - *iter_limit = (cache_bits > 0) ? iter_neg : iter_neg / 2; -} - static int HashChainFindCopy(const HashChain* const p, - int base_position, int xsize_signed, - const uint32_t* const argb, int max_len, - int window_size, int iter_pos, int iter_limit, + int quality, int index, int xsize, + const uint32_t* const argb, int maxlen, int* const distance_ptr, int* const length_ptr) { - const uint32_t* const argb_start = argb + base_position; - uint64_t best_val = 0; - uint32_t best_length = 1; - uint32_t best_distance = 0; - const uint32_t xsize = (uint32_t)xsize_signed; - const int min_pos = - (base_position > window_size) ? base_position - window_size : 0; + const uint64_t hash_code = GetPixPairHash64(&argb[index]); + int prev_length = 0; + int64_t best_val = 0; + int best_length = 0; + int best_distance = 0; + const uint32_t* const argb_start = argb + index; + const int iter_min_mult = (quality < 50) ? 2 : (quality < 75) ? 4 : 8; + const int iter_min = -quality * iter_min_mult; + int iter_cnt = 10 + (quality >> 1); + const int min_pos = (index > WINDOW_SIZE) ? index - WINDOW_SIZE : 0; int pos; + assert(xsize > 0); - if (max_len > MAX_LENGTH) { - max_len = MAX_LENGTH; - } - for (pos = p->hash_to_first_index_[GetPixPairHash64(argb_start)]; + for (pos = p->hash_to_first_index_[hash_code]; pos >= min_pos; pos = p->chain_[pos]) { - uint64_t val; - uint32_t curr_length; - uint32_t distance; - const uint64_t* const ptr1 = - (const uint64_t*)(argb + pos + best_length - 1); - const uint64_t* const ptr2 = - (const uint64_t*)(argb_start + best_length - 1); - - if (iter_pos < 0) { - if (iter_pos < iter_limit || best_val >= 0xff0000) { + int64_t val; + int curr_length; + if (iter_cnt < 0) { + if (iter_cnt < iter_min || best_val >= 0xff0000) { break; } } - --iter_pos; - - // Before 'expensive' linear match, check if the two arrays match at the - // current best length index and also for the succeeding elements. - if (*ptr1 != *ptr2) continue; - - curr_length = FindMatchLength(argb + pos, argb_start, max_len); - if (curr_length < best_length) continue; - - distance = (uint32_t)(base_position - pos); - val = curr_length << 16; + --iter_cnt; + if (best_length != 0 && + argb[pos + best_length - 1] != argb_start[best_length - 1]) { + continue; + } + curr_length = FindMatchLength(argb + pos, argb_start, maxlen); + if (curr_length < prev_length) { + continue; + } + val = 65536 * curr_length; // Favoring 2d locality here gives savings for certain images. - if (distance < 9 * xsize) { - const uint32_t y = distance / xsize; - uint32_t x = distance % xsize; - if (x > (xsize >> 1)) { + if (index - pos < 9 * xsize) { + const int y = (index - pos) / xsize; + int x = (index - pos) % xsize; + if (x > xsize / 2) { x = xsize - x; } - if (x <= 7) { - val += 9 * 9 + 9 * 9; + if (x <= 7 && x >= -8) { val -= y * y + x * x; + } else { + val -= 9 * 9 + 9 * 9; } + } else { + val -= 9 * 9 + 9 * 9; } if (best_val < val) { + prev_length = curr_length; best_val = val; best_length = curr_length; - best_distance = distance; - if (curr_length >= (uint32_t)max_len) { + best_distance = index - pos; + if (curr_length >= MAX_LENGTH) { break; } - if ((best_distance == 1 || distance == xsize) && + if ((best_distance == 1 || best_distance == xsize) && best_length >= 128) { break; } } } - *distance_ptr = (int)best_distance; + *distance_ptr = best_distance; *length_ptr = best_length; return (best_length >= MIN_LENGTH); } @@ -280,9 +257,6 @@ static int BackwardReferencesHashChain(int xsize, int ysize, const int pix_count = xsize * ysize; HashChain* const hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); VP8LColorCache hashers; - int window_size = WINDOW_SIZE; - int iter_pos = 1; - int iter_limit = -1; if (hash_chain == NULL) return 0; if (use_color_cache) { @@ -293,16 +267,16 @@ static int BackwardReferencesHashChain(int xsize, int ysize, if (!HashChainInit(hash_chain, pix_count)) goto Error; refs->size = 0; - GetParamsForHashChainFindCopy(quality, xsize, cache_bits, - &window_size, &iter_pos, &iter_limit); for (i = 0; i < pix_count; ) { // Alternative#1: Code the pixels starting at 'i' using backward reference. int offset = 0; int len = 0; if (i < pix_count - 1) { // FindCopy(i,..) reads pixels at [i] and [i + 1]. - int max_len = pix_count - i; - HashChainFindCopy(hash_chain, i, xsize, argb, max_len, - window_size, iter_pos, iter_limit, + int maxlen = pix_count - i; + if (maxlen > MAX_LENGTH) { + maxlen = MAX_LENGTH; + } + HashChainFindCopy(hash_chain, quality, i, xsize, argb, maxlen, &offset, &len); } if (len >= MIN_LENGTH) { @@ -313,10 +287,12 @@ static int BackwardReferencesHashChain(int xsize, int ysize, int k; HashChainInsert(hash_chain, &argb[i], i); if (i < pix_count - 2) { // FindCopy(i+1,..) reads [i + 1] and [i + 2]. - int max_len = pix_count - (i + 1); - HashChainFindCopy(hash_chain, i + 1, xsize, argb, max_len, - window_size, iter_pos, iter_limit, - &offset2, &len2); + int maxlen = pix_count - (i + 1); + if (maxlen > MAX_LENGTH) { + maxlen = MAX_LENGTH; + } + HashChainFindCopy(hash_chain, quality, + i + 1, xsize, argb, maxlen, &offset2, &len2); if (len2 > len + 1) { const uint32_t pixel = argb[i]; // Alternative#2 is a better match. So push pixel at 'i' as literal. @@ -324,10 +300,10 @@ static int BackwardReferencesHashChain(int xsize, int ysize, const int ix = VP8LColorCacheGetIndex(&hashers, pixel); refs->refs[refs->size] = PixOrCopyCreateCacheIdx(ix); } else { - if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); refs->refs[refs->size] = PixOrCopyCreateLiteral(pixel); } ++refs->size; + if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); i++; // Backward reference to be done for next pixel. len = len2; offset = offset2; @@ -357,10 +333,10 @@ static int BackwardReferencesHashChain(int xsize, int ysize, const int ix = VP8LColorCacheGetIndex(&hashers, pixel); refs->refs[refs->size] = PixOrCopyCreateCacheIdx(ix); } else { - if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); refs->refs[refs->size] = PixOrCopyCreateLiteral(pixel); } ++refs->size; + if (use_color_cache) VP8LColorCacheInsert(&hashers, pixel); if (i + 1 < pix_count) { HashChainInsert(hash_chain, &argb[i], i); } @@ -386,8 +362,7 @@ typedef struct { static int BackwardReferencesTraceBackwards( int xsize, int ysize, int recursive_cost_model, - const uint32_t* const argb, int quality, int cache_bits, - VP8LBackwardRefs* const refs); + const uint32_t* const argb, int cache_bits, VP8LBackwardRefs* const refs); static void ConvertPopulationCountTableToBitEstimates( int num_symbols, const int population_counts[], double output[]) { @@ -412,16 +387,17 @@ static void ConvertPopulationCountTableToBitEstimates( static int CostModelBuild(CostModel* const m, int xsize, int ysize, int recursion_level, const uint32_t* const argb, - int quality, int cache_bits) { + int cache_bits) { int ok = 0; VP8LHistogram histo; VP8LBackwardRefs refs; + const int quality = 100; if (!VP8LBackwardRefsAlloc(&refs, xsize * ysize)) goto Error; if (recursion_level > 0) { if (!BackwardReferencesTraceBackwards(xsize, ysize, recursion_level - 1, - argb, quality, cache_bits, &refs)) { + argb, cache_bits, &refs)) { goto Error; } } else { @@ -462,37 +438,34 @@ static WEBP_INLINE double GetCacheCost(const CostModel* const m, uint32_t idx) { static WEBP_INLINE double GetLengthCost(const CostModel* const m, uint32_t length) { - int code, extra_bits; - VP8LPrefixEncodeBits(length, &code, &extra_bits); - return m->literal_[VALUES_IN_BYTE + code] + extra_bits; + int code, extra_bits_count, extra_bits_value; + PrefixEncode(length, &code, &extra_bits_count, &extra_bits_value); + return m->literal_[VALUES_IN_BYTE + code] + extra_bits_count; } static WEBP_INLINE double GetDistanceCost(const CostModel* const m, uint32_t distance) { - int code, extra_bits; - VP8LPrefixEncodeBits(distance, &code, &extra_bits); - return m->distance_[code] + extra_bits; + int code, extra_bits_count, extra_bits_value; + PrefixEncode(distance, &code, &extra_bits_count, &extra_bits_value); + return m->distance_[code] + extra_bits_count; } static int BackwardReferencesHashChainDistanceOnly( int xsize, int ysize, int recursive_cost_model, const uint32_t* const argb, - int quality, int cache_bits, uint32_t* const dist_array) { + int cache_bits, uint32_t* const dist_array) { int i; int ok = 0; int cc_init = 0; + const int quality = 100; const int pix_count = xsize * ysize; const int use_color_cache = (cache_bits > 0); - float* const cost = - (float*)WebPSafeMalloc((uint64_t)pix_count, sizeof(*cost)); + double* const cost = + (double*)WebPSafeMalloc((uint64_t)pix_count, sizeof(*cost)); CostModel* cost_model = (CostModel*)malloc(sizeof(*cost_model)); HashChain* hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); VP8LColorCache hashers; const double mul0 = (recursive_cost_model != 0) ? 1.0 : 0.68; const double mul1 = (recursive_cost_model != 0) ? 1.0 : 0.82; - const int min_distance_code = 2; // TODO(vikasa): tune as function of quality - int window_size = WINDOW_SIZE; - int iter_pos = 1; - int iter_limit = -1; if (cost == NULL || cost_model == NULL || hash_chain == NULL) goto Error; @@ -504,17 +477,15 @@ static int BackwardReferencesHashChainDistanceOnly( } if (!CostModelBuild(cost_model, xsize, ysize, recursive_cost_model, argb, - quality, cache_bits)) { + cache_bits)) { goto Error; } - for (i = 0; i < pix_count; ++i) cost[i] = 1e38f; + for (i = 0; i < pix_count; ++i) cost[i] = 1e100; // We loop one pixel at a time, but store all currently best points to // non-processed locations from this point. dist_array[0] = 0; - GetParamsForHashChainFindCopy(quality, xsize, cache_bits, - &window_size, &iter_pos, &iter_limit); for (i = 0; i < pix_count; ++i) { double prev_cost = 0.0; int shortmax; @@ -525,9 +496,11 @@ static int BackwardReferencesHashChainDistanceOnly( int offset = 0; int len = 0; if (i < pix_count - 1) { // FindCopy reads pixels at [i] and [i + 1]. - int max_len = shortmax ? 2 : pix_count - i; - HashChainFindCopy(hash_chain, i, xsize, argb, max_len, - window_size, iter_pos, iter_limit, + int maxlen = shortmax ? 2 : MAX_LENGTH; + if (maxlen > pix_count - i) { + maxlen = pix_count - i; + } + HashChainFindCopy(hash_chain, quality, i, xsize, argb, maxlen, &offset, &len); } if (len >= MIN_LENGTH) { @@ -536,15 +509,16 @@ static int BackwardReferencesHashChainDistanceOnly( prev_cost + GetDistanceCost(cost_model, code); int k; for (k = 1; k < len; ++k) { - const double cost_val = distance_cost + GetLengthCost(cost_model, k); + const double cost_val = + distance_cost + GetLengthCost(cost_model, k); if (cost[i + k] > cost_val) { - cost[i + k] = (float)cost_val; + cost[i + k] = cost_val; dist_array[i + k] = k + 1; } } // This if is for speedup only. It roughly doubles the speed, and // makes compression worse by .1 %. - if (len >= 128 && code <= min_distance_code) { + if (len >= 128 && code < 2) { // Long copy for short distances, let's skip the middle // lookups for better copies. // 1) insert the hashes. @@ -555,10 +529,10 @@ static int BackwardReferencesHashChainDistanceOnly( } // 2) Add to the hash_chain (but cannot add the last pixel) { - const int last = (len + i < pix_count - 1) ? len + i - : pix_count - 1; - for (k = i; k < last; ++k) { - HashChainInsert(hash_chain, &argb[k], k); + const int last = (len < pix_count - 1 - i) ? len + : pix_count - 1 - i; + for (k = 0; k < last; ++k) { + HashChainInsert(hash_chain, &argb[i + k], i + k); } } // 3) jump. @@ -577,13 +551,13 @@ static int BackwardReferencesHashChainDistanceOnly( const int ix = VP8LColorCacheGetIndex(&hashers, argb[i]); cost_val += GetCacheCost(cost_model, ix) * mul0; } else { - if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); cost_val += GetLiteralCost(cost_model, argb[i]) * mul1; } if (cost[i] > cost_val) { - cost[i] = (float)cost_val; + cost[i] = cost_val; dist_array[i] = 1; // only one is inserted. } + if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); } next_symbol: ; } @@ -598,30 +572,40 @@ Error: return ok; } -// We pack the path at the end of *dist_array and return -// a pointer to this part of the array. Example: -// dist_array = [1x2xx3x2] => packed [1x2x1232], chosen_path = [1232] -static void TraceBackwards(uint32_t* const dist_array, - int dist_array_size, - uint32_t** const chosen_path, - int* const chosen_path_size) { - uint32_t* path = dist_array + dist_array_size; - uint32_t* cur = dist_array + dist_array_size - 1; - while (cur >= dist_array) { - const int k = *cur; - --path; - *path = k; - cur -= k; - } - *chosen_path = path; - *chosen_path_size = (int)(dist_array + dist_array_size - path); +static int TraceBackwards(const uint32_t* const dist_array, + int dist_array_size, + uint32_t** const chosen_path, + int* const chosen_path_size) { + int i; + // Count how many. + int count = 0; + for (i = dist_array_size - 1; i >= 0; ) { + int k = dist_array[i]; + assert(k >= 1); + ++count; + i -= k; + } + // Allocate. + *chosen_path_size = count; + *chosen_path = + (uint32_t*)WebPSafeMalloc((uint64_t)count, sizeof(**chosen_path)); + if (*chosen_path == NULL) return 0; + + // Write in reverse order. + for (i = dist_array_size - 1; i >= 0; ) { + int k = dist_array[i]; + assert(k >= 1); + (*chosen_path)[--count] = k; + i -= k; + } + return 1; } static int BackwardReferencesHashChainFollowChosenPath( - int xsize, int ysize, const uint32_t* const argb, - int quality, int cache_bits, + int xsize, int ysize, const uint32_t* const argb, int cache_bits, const uint32_t* const chosen_path, int chosen_path_size, VP8LBackwardRefs* const refs) { + const int quality = 100; const int pix_count = xsize * ysize; const int use_color_cache = (cache_bits > 0); int size = 0; @@ -630,9 +614,6 @@ static int BackwardReferencesHashChainFollowChosenPath( int ix; int ok = 0; int cc_init = 0; - int window_size = WINDOW_SIZE; - int iter_pos = 1; - int iter_limit = -1; HashChain* hash_chain = (HashChain*)malloc(sizeof(*hash_chain)); VP8LColorCache hashers; @@ -645,17 +626,14 @@ static int BackwardReferencesHashChainFollowChosenPath( } refs->size = 0; - GetParamsForHashChainFindCopy(quality, xsize, cache_bits, - &window_size, &iter_pos, &iter_limit); for (ix = 0; ix < chosen_path_size; ++ix, ++size) { int offset = 0; int len = 0; - int max_len = chosen_path[ix]; - if (max_len != 1) { - HashChainFindCopy(hash_chain, i, xsize, argb, max_len, - window_size, iter_pos, iter_limit, - &offset, &len); - assert(len == max_len); + int maxlen = chosen_path[ix]; + if (maxlen != 1) { + HashChainFindCopy(hash_chain, quality, + i, xsize, argb, maxlen, &offset, &len); + assert(len == maxlen); refs->refs[size] = PixOrCopyCreateCopy(offset, len); if (use_color_cache) { for (k = 0; k < len; ++k) { @@ -675,9 +653,9 @@ static int BackwardReferencesHashChainFollowChosenPath( const int idx = VP8LColorCacheGetIndex(&hashers, argb[i]); refs->refs[size] = PixOrCopyCreateCacheIdx(idx); } else { - if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); refs->refs[size] = PixOrCopyCreateLiteral(argb[i]); } + if (use_color_cache) VP8LColorCacheInsert(&hashers, argb[i]); if (i + 1 < pix_count) { HashChainInsert(hash_chain, &argb[i], i); } @@ -697,7 +675,7 @@ Error: static int BackwardReferencesTraceBackwards(int xsize, int ysize, int recursive_cost_model, const uint32_t* const argb, - int quality, int cache_bits, + int cache_bits, VP8LBackwardRefs* const refs) { int ok = 0; const int dist_array_size = xsize * ysize; @@ -709,18 +687,22 @@ static int BackwardReferencesTraceBackwards(int xsize, int ysize, if (dist_array == NULL) goto Error; if (!BackwardReferencesHashChainDistanceOnly( - xsize, ysize, recursive_cost_model, argb, quality, cache_bits, - dist_array)) { + xsize, ysize, recursive_cost_model, argb, cache_bits, dist_array)) { + goto Error; + } + if (!TraceBackwards(dist_array, dist_array_size, + &chosen_path, &chosen_path_size)) { goto Error; } - TraceBackwards(dist_array, dist_array_size, &chosen_path, &chosen_path_size); + free(dist_array); // no need to retain this memory any longer + dist_array = NULL; if (!BackwardReferencesHashChainFollowChosenPath( - xsize, ysize, argb, quality, cache_bits, chosen_path, chosen_path_size, - refs)) { + xsize, ysize, argb, cache_bits, chosen_path, chosen_path_size, refs)) { goto Error; } ok = 1; Error: + free(chosen_path); free(dist_array); return ok; } @@ -780,20 +762,18 @@ int VP8LGetBackwardReferences(int width, int height, // Choose appropriate backward reference. if (lz77_is_useful) { - // TraceBackwards is costly. Don't execute it at lower quality. - const int try_lz77_trace_backwards = (quality >= 25); + // TraceBackwards is costly. Run it for higher qualities. + const int try_lz77_trace_backwards = (quality >= 75); *best = refs_lz77; // default guess: lz77 is better VP8LClearBackwardRefs(&refs_rle); if (try_lz77_trace_backwards) { - // Set recursion level for large images using a color cache. - const int recursion_level = - (num_pix < 320 * 200) && (cache_bits > 0) ? 1 : 0; + const int recursion_level = (num_pix < 320 * 200) ? 1 : 0; VP8LBackwardRefs refs_trace; if (!VP8LBackwardRefsAlloc(&refs_trace, num_pix)) { goto End; } - if (BackwardReferencesTraceBackwards(width, height, recursion_level, argb, - quality, cache_bits, &refs_trace)) { + if (BackwardReferencesTraceBackwards( + width, height, recursion_level, argb, cache_bits, &refs_trace)) { VP8LClearBackwardRefs(&refs_lz77); *best = refs_trace; } |