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method=0: Don't evaluate any predictor

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and apply Paeth predictor (predictor#11) for the low effort (m=0) mode.

For 1000 image PNG corpus (m=0), this change yields speedup of 25% at lower quality
range and about 10% for higher quality range.

Change-Id: I0f036b8ffe45c241e63a067cbf01527b13d8de93
This commit is contained in:
Pascal Massimino 2014-12-17 18:41:08 +01:00
parent 6f4fcb983e
commit 87c3d53180
1 changed files with 7 additions and 7 deletions
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14
src/dsp/lossless.c
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@ -758,12 +758,9 @@ static WEBP_INLINE void UpdateHisto(int histo_argb[4][256], uint32_t argb) {
static int GetBestPredictorForTile(int width, int height,
int tile_x, int tile_y, int bits,
int low_effort,
const int accumulated[4][256],
const uint32_t* const argb_scratch) {
const int kNumPredModes = 14;
const int kPredModePaeth = 11;
const int start_mode = low_effort ? kPredModePaeth : 0;
const int col_start = tile_x << bits;
const int row_start = tile_y << bits;
const int tile_size = 1 << bits;
@ -772,7 +769,7 @@ static int GetBestPredictorForTile(int width, int height,
float best_diff = MAX_DIFF_COST;
int best_mode = 0;
int mode;
for (mode = start_mode; mode < kNumPredModes; ++mode) {
for (mode = 0; mode < kNumPredModes; ++mode) {
const uint32_t* current_row = argb_scratch;
const VP8LPredictorFunc pred_func = VP8LPredictors[mode];
float cur_diff;
@ -848,6 +845,7 @@ void VP8LResidualImage(int width, int height, int bits, int low_effort,
const int max_tile_size = 1 << bits;
const int tiles_per_row = VP8LSubSampleSize(width, bits);
const int tiles_per_col = VP8LSubSampleSize(height, bits);
const int kPredLowEffort = 11;
uint32_t* const upper_row = argb_scratch;
uint32_t* const current_tile_rows = argb_scratch + width;
int tile_y;
@ -872,9 +870,11 @@ void VP8LResidualImage(int width, int height, int bits, int low_effort,
if (all_x_max > width) {
all_x_max = width;
}
pred = GetBestPredictorForTile(width, height, tile_x, tile_y, bits,
low_effort, (const int (*)[256])histo,
argb_scratch);
pred = low_effort ? kPredLowEffort :
GetBestPredictorForTile(width, height, tile_x,
tile_y, bits,
(const int (*)[256])histo,
argb_scratch);
image[tile_y * tiles_per_row + tile_x] = 0xff000000u | (pred << 8);
CopyTileWithPrediction(width, height, tile_x, tile_y, bits, pred,
argb_scratch, argb);