dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-12-27 06:08:21 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Optimize BackwardReferenceHashChainFollowPath.

Browse Source 
Instead of calling HashChainFindMethod, call a new (subset) method
HashChainFindOffset to get the offset/distance for a given length.

The encoding is tad faster at default compression

                       Before              After
                     bpp/rate            bpp/rate
442 Palette     0.2720/5.270 MP/s      0.2720/5.790 MP/s
558 non-palette 3.7607/0.797 MP/s      3.7607/0.816 MP/s

Change-Id: If4041a9c18f7e972f49fcbab8c3e2f013d8bf1cf
This commit is contained in:
Vikas Arora 2014-10-20 23:44:01 -07:00
parent 5f36b68d22
commit 139142e440
1 changed files with 22 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
src/enc/backward_references.c
View File

@ -245,6 +245,24 @@ static void GetParamsForHashChainFindCopy(int quality, int xsize,
*iter_limit = (cache_bits > 0) ? iter_neg : iter_neg / 2;
}
static void HashChainFindOffset(const VP8LHashChain* const p, int base_position,
const uint32_t* const argb, int len,
int window_size, int* const distance_ptr) {
const uint32_t* const argb_start = argb + base_position;
const int min_pos =
(base_position > window_size) ? base_position - window_size : 0;
int pos;
assert(len <= MAX_LENGTH);
for (pos = p->hash_to_first_index_[GetPixPairHash64(argb_start)];
pos >= min_pos;
pos = p->chain_[pos]) {
const int curr_length =
FindMatchLength(argb + pos, argb_start, len - 1, len);
if (curr_length == len) break;
}
*distance_ptr = base_position - pos;
}
static int HashChainFindCopy(const VP8LHashChain* const p,
int base_position, int xsize,
const uint32_t* const argb, int max_len,
@ -276,7 +294,7 @@ static int HashChainFindCopy(const VP8LHashChain* const p,
curr_length = FindMatchLength(argb + pos, argb_start, best_length, max_len);
if (curr_length < best_length) continue;
distance = (uint32_t)(base_position - pos);
distance = base_position - pos;
if (best_length < curr_length) {
best_length = curr_length;
best_distance = distance;
@ -688,13 +706,9 @@ static int BackwardReferencesHashChainFollowChosenPath(
HashChainInit(hash_chain);
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);
const int len = chosen_path[ix];
if (len != 1) {
HashChainFindOffset(hash_chain, i, argb, len, window_size, &offset);
BackwardRefsCursorAdd(refs, PixOrCopyCreateCopy(offset, len));
if (use_color_cache) {
for (k = 0; k < len; ++k) {