mirror of
https://github.com/webmproject/libwebp.git
synced 2024-12-26 05:38:22 +01:00
Tune Lossless encoder
- Changed the dynamic range where more aggressive (BackwardReferencesTraceBackward) heuristic is run from quality > 10 (instead of quality > 25). - Limit the backward-ref Window size to 16*width & 256*width for lower qualities ([0, 25[ & [25, 50[) respectively, instead of 1M window. - Evaluate the params for HashChainFindCopy outside this function call and pass it, instead of recomputing them for every call. Change-Id: If9eedfc14b978e7632d7cf69c96186e2910b0554
This commit is contained in:
vikas arora
parent
3bb4bbeb60
commit
ab5ea217f7
@ -141,9 +141,25 @@ static void HashChainInsert(HashChain* const p,
|
||||
p->hash_to_first_index_[hash_code] = pos;
|
||||
}
|
||||
|
||||
static void GetParamsForHashChainFindCopy(int quality, int xsize,
|
||||
int* window_size, int* iter_pos,
|
||||
int* iter_limit) {
|
||||
const int iter_mult = (quality < 27) ? 1 : 1 + ((quality - 27) >> 4);
|
||||
// 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 = 5 + (quality >> 3);
|
||||
*iter_limit = -quality * iter_mult;
|
||||
}
|
||||
|
||||
static int HashChainFindCopy(const HashChain* const p,
|
||||
int quality, int index, int xsize,
|
||||
int index, int xsize,
|
||||
const uint32_t* const argb, int maxlen,
|
||||
int window_size, int iter_pos, int iter_limit,
|
||||
int* const distance_ptr,
|
||||
int* const length_ptr) {
|
||||
const uint64_t hash_code = GetPixPairHash64(&argb[index]);
|
||||
@ -152,10 +168,7 @@ static int HashChainFindCopy(const HashChain* const p,
|
||||
int best_length = 0;
|
||||
int best_distance = 0;
|
||||
const uint32_t* const argb_start = argb + index;
|
||||
const int iter_min_mult = (quality < 36) ? 1 : 1 + ((quality - 36) >> 3);
|
||||
const int iter_min = -quality * iter_min_mult;
|
||||
int iter_cnt = 10 + (quality >> 2);
|
||||
const int min_pos = (index > WINDOW_SIZE) ? index - WINDOW_SIZE : 0;
|
||||
const int min_pos = (index > window_size) ? index - window_size : 0;
|
||||
int pos;
|
||||
|
||||
assert(xsize > 0);
|
||||
@ -164,12 +177,12 @@ static int HashChainFindCopy(const HashChain* const p,
|
||||
pos = p->chain_[pos]) {
|
||||
int64_t val;
|
||||
int curr_length;
|
||||
if (iter_cnt < 0) {
|
||||
if (iter_cnt < iter_min || best_val >= 0xff0000) {
|
||||
if (iter_pos < 0) {
|
||||
if (iter_pos < iter_limit || best_val >= 0xff0000) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
--iter_cnt;
|
||||
--iter_pos;
|
||||
if (best_length != 0 &&
|
||||
argb[pos + best_length - 1] != argb_start[best_length - 1]) {
|
||||
continue;
|
||||
@ -257,6 +270,9 @@ 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) {
|
||||
@ -267,6 +283,8 @@ static int BackwardReferencesHashChain(int xsize, int ysize,
|
||||
if (!HashChainInit(hash_chain, pix_count)) goto Error;
|
||||
|
||||
refs->size = 0;
|
||||
GetParamsForHashChainFindCopy(quality, xsize, &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;
|
||||
@ -276,7 +294,8 @@ static int BackwardReferencesHashChain(int xsize, int ysize,
|
||||
if (maxlen > MAX_LENGTH) {
|
||||
maxlen = MAX_LENGTH;
|
||||
}
|
||||
HashChainFindCopy(hash_chain, quality, i, xsize, argb, maxlen,
|
||||
HashChainFindCopy(hash_chain, i, xsize, argb, maxlen,
|
||||
window_size, iter_pos, iter_limit,
|
||||
&offset, &len);
|
||||
}
|
||||
if (len >= MIN_LENGTH) {
|
||||
@ -291,8 +310,9 @@ static int BackwardReferencesHashChain(int xsize, int ysize,
|
||||
if (maxlen > MAX_LENGTH) {
|
||||
maxlen = MAX_LENGTH;
|
||||
}
|
||||
HashChainFindCopy(hash_chain, quality,
|
||||
i + 1, xsize, argb, maxlen, &offset2, &len2);
|
||||
HashChainFindCopy(hash_chain, i + 1, xsize, argb, maxlen,
|
||||
window_size, iter_pos, iter_limit,
|
||||
&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.
|
||||
@ -465,6 +485,9 @@ static int BackwardReferencesHashChainDistanceOnly(
|
||||
VP8LColorCache hashers;
|
||||
const double mul0 = (recursive_cost_model != 0) ? 1.0 : 0.68;
|
||||
const double mul1 = (recursive_cost_model != 0) ? 1.0 : 0.82;
|
||||
int window_size = WINDOW_SIZE;
|
||||
int iter_pos = 1;
|
||||
int iter_limit = -1;
|
||||
|
||||
if (cost == NULL || cost_model == NULL || hash_chain == NULL) goto Error;
|
||||
|
||||
@ -485,6 +508,8 @@ static int BackwardReferencesHashChainDistanceOnly(
|
||||
// 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, &window_size, &iter_pos,
|
||||
&iter_limit);
|
||||
for (i = 0; i < pix_count; ++i) {
|
||||
double prev_cost = 0.0;
|
||||
int shortmax;
|
||||
@ -499,7 +524,8 @@ static int BackwardReferencesHashChainDistanceOnly(
|
||||
if (maxlen > pix_count - i) {
|
||||
maxlen = pix_count - i;
|
||||
}
|
||||
HashChainFindCopy(hash_chain, quality, i, xsize, argb, maxlen,
|
||||
HashChainFindCopy(hash_chain, i, xsize, argb, maxlen,
|
||||
window_size, iter_pos, iter_limit,
|
||||
&offset, &len);
|
||||
}
|
||||
if (len >= MIN_LENGTH) {
|
||||
@ -612,6 +638,9 @@ 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;
|
||||
|
||||
@ -624,13 +653,16 @@ static int BackwardReferencesHashChainFollowChosenPath(
|
||||
}
|
||||
|
||||
refs->size = 0;
|
||||
GetParamsForHashChainFindCopy(quality, xsize, &window_size, &iter_pos,
|
||||
&iter_limit);
|
||||
for (ix = 0; ix < chosen_path_size; ++ix, ++size) {
|
||||
int offset = 0;
|
||||
int len = 0;
|
||||
int maxlen = chosen_path[ix];
|
||||
if (maxlen != 1) {
|
||||
HashChainFindCopy(hash_chain, quality,
|
||||
i, xsize, argb, maxlen, &offset, &len);
|
||||
HashChainFindCopy(hash_chain, i, xsize, argb, maxlen,
|
||||
window_size, iter_pos, iter_limit,
|
||||
&offset, &len);
|
||||
assert(len == maxlen);
|
||||
refs->refs[size] = PixOrCopyCreateCopy(offset, len);
|
||||
if (use_color_cache) {
|
||||
@ -762,8 +794,8 @@ int VP8LGetBackwardReferences(int width, int height,
|
||||
|
||||
// Choose appropriate backward reference.
|
||||
if (lz77_is_useful) {
|
||||
// TraceBackwards is costly. Don't execute it at lower quality (q <= 25).
|
||||
const int try_lz77_trace_backwards = (quality > 25);
|
||||
// TraceBackwards is costly. Don't execute it at lower quality (q <= 10).
|
||||
const int try_lz77_trace_backwards = (quality > 10);
|
||||
*best = refs_lz77; // default guess: lz77 is better
|
||||
VP8LClearBackwardRefs(&refs_rle);
|
||||
if (try_lz77_trace_backwards) {
|
||||
|
||||
Loading…
Reference in New Issue
Block a user