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WebPAnimEncoder: choose max diff for framerect based on quality.

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We pick a mapping with quality 0 mapping to max diff 32, to quality 100
mapping to max_diff 1.

For 6k GIF image set, this improves compression by:
4% at quality 0
0.05% at quality 75

Benefits the MovingThumbnailer test videos too.

Change-Id: I6838ce864d41e1e65311d26b9b8115a12390a253
This commit is contained in:
Urvang Joshi 2016-03-29 22:19:44 +00:00 committed by James Zern
parent ff0a94beda
commit eb423903a4
1 changed files with 12 additions and 3 deletions
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15
src/mux/anim_encode.c
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@ -12,6 +12,7 @@
#include <assert.h>
#include <limits.h>
#include <math.h> // for pow()
#include <stdio.h>
#include <stdlib.h> // for abs()
@ -400,6 +401,12 @@ static int IsEmptyRect(const FrameRect* const rect) {
return (rect->width_ == 0) || (rect->height_ == 0);
}
static int QualityToMaxDiff(float quality) {
const double val = pow(quality / 100., 0.5);
const double max_diff = 31 * (1 - val) + 1 * val;
return (int)(max_diff + 0.5);
}
// Assumes that an initial valid guess of change rectangle 'rect' is passed.
static void MinimizeChangeRectangle(const WebPPicture* const src,
const WebPPicture* const dst,
@ -408,10 +415,8 @@ static void MinimizeChangeRectangle(const WebPPicture* const src,
int i, j;
const ComparePixelsFunc compare_pixels =
is_lossless ? ComparePixelsLossless : ComparePixelsLossy;
// TODO(urvang): For lossy, pick max_allowed_diff based on quality.
const int max_allowed_diff_lossy = 0;
const int max_allowed_diff_lossy = QualityToMaxDiff(quality);
const int max_allowed_diff = is_lossless ? 0 : max_allowed_diff_lossy;
(void)quality;
// Sanity checks.
assert(src->width == dst->width && src->height == dst->height);
@ -1335,6 +1340,10 @@ int WebPAnimEncoderAdd(WebPAnimEncoder* enc, WebPPicture* frame, int timestamp,
}
if (encoder_config != NULL) {
if (!WebPValidateConfig(encoder_config)) {
MarkError(enc, "ERROR adding frame: Invalid WebPConfig");
return 0;
}
config = *encoder_config;
} else {
WebPConfigInit(&config);