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3% speed improvement for lossless webp encoder for low effort mode:

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prevent updating unused histogram.

Benchmark on 1000 PNGs, 30 iterations, lossless, quality 0, method 0:
before: Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 34.578 MP/s
after: Compression (output/input): 2.9120/3.2667 bpp, Encode rate (raw data): 36.980 MP/s

Change-Id: Id62759d4d111a6ba41c85c611a15d4f6ffc9f935
This commit is contained in:
Lode Vandevenne 2015-11-21 17:00:14 +01:00 committed by Pascal Massimino
parent 21735e06f7
commit b8c44f1aa4
1 changed files with 11 additions and 9 deletions
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20
src/dsp/lossless_enc.c
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@ -692,7 +692,7 @@ void VP8LResidualImage(int width, int height, int bits, int low_effort,
uint32_t* const current_tile_rows = argb_scratch + width;
int tile_y;
int histo[4][256];
memset(histo, 0, sizeof(histo));
if (!low_effort) memset(histo, 0, sizeof(histo));
for (tile_y = 0; tile_y < tiles_per_col; ++tile_y) {
const int tile_y_offset = tile_y * max_tile_size;
const int this_tile_height =
@ -720,14 +720,16 @@ void VP8LResidualImage(int width, int height, int bits, int low_effort,
image[tile_y * tiles_per_row + tile_x] = 0xff000000u | (pred << 8);
CopyTileWithPrediction(width, height, tile_x, tile_y, bits, pred,
argb_scratch, argb);
for (y = 0; y < max_tile_size; ++y) {
int all_x;
int all_y = tile_y_offset + y;
if (all_y >= height) {
break;
}
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x) {
UpdateHisto(histo, argb[all_y * width + all_x]);
if (!low_effort) {
for (y = 0; y < max_tile_size; ++y) {
int all_x;
int all_y = tile_y_offset + y;
if (all_y >= height) {
break;
}
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x) {
UpdateHisto(histo, argb[all_y * width + all_x]);
}
}
}
}