dany/libwebp
1
0
Fork 0
mirror of https://github.com/webmproject/libwebp.git synced 2024-12-25 13:18:22 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

Tune lossless compression to get better gains.

Browse Source 
Tune compression heuristics to get better gains across wide quality range.

Change-Id: Ic342d4dbcf83fe2086a34e5c184aef0714109430
This commit is contained in:
Vikas Arora 2012-10-05 09:55:06 -07:00
parent ce8bff45bc
commit 7b3eb372ad
1 changed files with 19 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
src/enc/backward_references.c
View File

@ -152,9 +152,9 @@ 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 < 50) ? 2 : (quality < 75) ? 4 : 8;
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 >> 1);
int iter_cnt = 10 + (quality >> 2);
const int min_pos = (index > WINDOW_SIZE) ? index - WINDOW_SIZE : 0;
int pos;
@ -362,7 +362,8 @@ typedef struct {
static int BackwardReferencesTraceBackwards(
int xsize, int ysize, int recursive_cost_model,
const uint32_t* const argb, int cache_bits, VP8LBackwardRefs* const refs);
const uint32_t* const argb, int quality, int cache_bits,
VP8LBackwardRefs* const refs);
static void ConvertPopulationCountTableToBitEstimates(
int num_symbols, const int population_counts[], double output[]) {
@ -387,17 +388,16 @@ static void ConvertPopulationCountTableToBitEstimates(
static int CostModelBuild(CostModel* const m, int xsize, int ysize,
int recursion_level, const uint32_t* const argb,
int cache_bits) {
int quality, 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, cache_bits, &refs)) {
argb, quality, cache_bits, &refs)) {
goto Error;
}
} else {
@ -452,11 +452,10 @@ static WEBP_INLINE double GetDistanceCost(const CostModel* const m,
static int BackwardReferencesHashChainDistanceOnly(
int xsize, int ysize, int recursive_cost_model, const uint32_t* const argb,
int cache_bits, uint32_t* const dist_array) {
int quality, 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 =
@ -477,7 +476,7 @@ static int BackwardReferencesHashChainDistanceOnly(
}
if (!CostModelBuild(cost_model, xsize, ysize, recursive_cost_model, argb,
cache_bits)) {
quality, cache_bits)) {
goto Error;
}
@ -601,10 +600,10 @@ static int TraceBackwards(const uint32_t* const dist_array,
}
static int BackwardReferencesHashChainFollowChosenPath(
int xsize, int ysize, const uint32_t* const argb, int cache_bits,
int xsize, int ysize, const uint32_t* const argb,
int quality, 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;
@ -674,7 +673,7 @@ Error:
static int BackwardReferencesTraceBackwards(int xsize, int ysize,
int recursive_cost_model,
const uint32_t* const argb,
int cache_bits,
int quality, int cache_bits,
VP8LBackwardRefs* const refs) {
int ok = 0;
const int dist_array_size = xsize * ysize;
@ -686,7 +685,8 @@ static int BackwardReferencesTraceBackwards(int xsize, int ysize,
if (dist_array == NULL) goto Error;
if (!BackwardReferencesHashChainDistanceOnly(
xsize, ysize, recursive_cost_model, argb, cache_bits, dist_array)) {
xsize, ysize, recursive_cost_model, argb, quality, cache_bits,
dist_array)) {
goto Error;
}
if (!TraceBackwards(dist_array, dist_array_size,
@ -696,7 +696,8 @@ static int BackwardReferencesTraceBackwards(int xsize, int ysize,
free(dist_array); // no need to retain this memory any longer
dist_array = NULL;
if (!BackwardReferencesHashChainFollowChosenPath(
xsize, ysize, argb, cache_bits, chosen_path, chosen_path_size, refs)) {
xsize, ysize, argb, quality, cache_bits, chosen_path, chosen_path_size,
refs)) {
goto Error;
}
ok = 1;
@ -761,8 +762,8 @@ int VP8LGetBackwardReferences(int width, int height,
// Choose appropriate backward reference.
if (lz77_is_useful) {
// TraceBackwards is costly. Run it for higher qualities.
const int try_lz77_trace_backwards = (quality >= 75);
// TraceBackwards is costly. Don't execute it at lower quality (q <= 25).
const int try_lz77_trace_backwards = (quality > 25);
*best = refs_lz77; // default guess: lz77 is better
VP8LClearBackwardRefs(&refs_rle);
if (try_lz77_trace_backwards) {
@ -771,8 +772,8 @@ int VP8LGetBackwardReferences(int width, int height,
if (!VP8LBackwardRefsAlloc(&refs_trace, num_pix)) {
goto End;
}
if (BackwardReferencesTraceBackwards(
width, height, recursion_level, argb, cache_bits, &refs_trace)) {
if (BackwardReferencesTraceBackwards(width, height, recursion_level, argb,
quality, cache_bits, &refs_trace)) {
VP8LClearBackwardRefs(&refs_lz77);
*best = refs_trace;
}