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gif2webp: Support a 'min' and 'max' key frame interval
Change-Id: If910c8849d7210e7227db0f45affa26fce7da102
This commit is contained in:
Urvang Joshi
360
examples/gif2webp_util.c
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360
examples/gif2webp_util.c
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// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Helper structs and methods for gif2webp tool.
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//
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#include <assert.h>
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#include <stdio.h>
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#include "webp/encode.h"
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#include "./gif2webp_util.h"
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#define DELTA_INFINITY 1ULL << 32
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#define KEYFRAME_NONE -1
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//------------------------------------------------------------------------------
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// Encoded frame.
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// Used to store two candidates of encoded data for an animation frame. One of
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// the two will be chosen later.
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typedef struct {
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WebPMuxFrameInfo sub_frame; // Encoded frame rectangle.
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WebPMuxFrameInfo key_frame; // Encoded frame if it was converted to keyframe.
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} EncodedFrame;
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// Release the data contained by 'encoded_frame'.
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static void FrameRelease(EncodedFrame* const encoded_frame) {
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WebPDataClear(&encoded_frame->sub_frame.bitstream);
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WebPDataClear(&encoded_frame->key_frame.bitstream);
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memset(encoded_frame, 0, sizeof(*encoded_frame));
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}
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//------------------------------------------------------------------------------
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// Frame cache.
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// Used to store encoded frames that haven't been output yet.
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struct WebPFrameCache {
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EncodedFrame* encoded_frames; // Array of encoded frames.
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size_t size; // Number of allocated data elements.
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size_t start; // Start index.
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size_t count; // Number of valid data elements.
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int flush_count; // If >0, ‘flush_count’ frames starting from
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// 'start' are ready to be added to mux.
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int64_t best_delta; // min(canvas size - frame size) over the frames.
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// Can be negative in certain cases due to
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// transparent pixels in a frame.
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int keyframe; // Index of selected keyframe relative to 'start'.
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size_t kmin; // Min distance between key frames.
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size_t kmax; // Max distance between key frames.
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size_t count_since_key_frame; // Frames seen since the last key frame.
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};
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// Reset the counters in the cache struct. Doesn't touch 'cache->encoded_frames'
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// and 'cache->size'.
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static void CacheReset(WebPFrameCache* const cache) {
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cache->start = 0;
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cache->count = 0;
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cache->flush_count = 0;
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cache->best_delta = DELTA_INFINITY;
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cache->keyframe = KEYFRAME_NONE;
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}
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WebPFrameCache* WebPFrameCacheNew(size_t kmin, size_t kmax) {
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WebPFrameCache* cache = (WebPFrameCache*)malloc(sizeof(*cache));
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if (cache == NULL) return NULL;
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CacheReset(cache);
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cache->kmin = kmin;
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cache->kmax = kmax;
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cache->count_since_key_frame = 0;
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cache->size = kmax - kmin;
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cache->encoded_frames =
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(EncodedFrame*)calloc(cache->size, sizeof(*cache->encoded_frames));
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if (cache->encoded_frames == NULL) return 0;
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return cache;
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}
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void WebPFrameCacheDelete(WebPFrameCache* const cache) {
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if (cache != NULL) {
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size_t i;
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for (i = 0; i < cache->size; ++i) {
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FrameRelease(&cache->encoded_frames[i]);
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}
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free(cache->encoded_frames);
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free(cache);
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}
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}
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static int EncodeFrame(const WebPConfig* const config, WebPPicture* const pic,
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WebPData* const encoded_data) {
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WebPMemoryWriter memory;
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pic->use_argb = 1;
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pic->writer = WebPMemoryWrite;
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pic->custom_ptr = &memory;
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WebPMemoryWriterInit(&memory);
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if (!WebPEncode(config, pic)) {
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return 0;
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}
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encoded_data->bytes = memory.mem;
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encoded_data->size = memory.size;
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return 1;
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}
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// Returns cached frame at given 'index'.
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static EncodedFrame* CacheGetFrame(const WebPFrameCache* const cache,
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size_t index) {
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assert(cache->start + index < cache->size);
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return &cache->encoded_frames[cache->start + index];
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}
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// Calculate the penalty incurred if we encode given frame as a key frame
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// instead of a sub-frame.
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static int64_t KeyFramePenalty(const EncodedFrame* const encoded_frame) {
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return ((int64_t)encoded_frame->key_frame.bitstream.size -
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encoded_frame->sub_frame.bitstream.size);
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}
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static int SetFrame(const WebPConfig* const config,
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const WebPMuxFrameInfo* const info, WebPPicture* const pic,
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WebPMuxFrameInfo* const dst) {
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*dst = *info;
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if (!EncodeFrame(config, pic, &dst->bitstream)) {
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return 0;
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}
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return 1;
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}
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int WebPFrameCacheAddFrame(WebPFrameCache* const cache,
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const WebPConfig* const config,
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const WebPMuxFrameInfo* const sub_frame_info,
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WebPPicture* const sub_frame_pic,
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const WebPMuxFrameInfo* const key_frame_info,
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WebPPicture* const key_frame_pic) {
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const size_t index = cache->count;
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EncodedFrame* const encoded_frame = CacheGetFrame(cache, index);
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assert(index < cache->size);
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assert(sub_frame_pic != NULL || key_frame_pic != NULL);
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if (sub_frame_pic != NULL && !SetFrame(config, sub_frame_info, sub_frame_pic,
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&encoded_frame->sub_frame)) {
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return 0;
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}
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if (key_frame_pic != NULL && !SetFrame(config, key_frame_info, key_frame_pic,
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&encoded_frame->key_frame)) {
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return 0;
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}
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++cache->count;
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if (sub_frame_pic == NULL && key_frame_pic != NULL) { // Keyframe.
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cache->keyframe = index;
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cache->flush_count = cache->count;
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cache->count_since_key_frame = 0;
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} else {
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++cache->count_since_key_frame;
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if (sub_frame_pic != NULL && key_frame_pic == NULL) { // Non-keyframe.
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assert(cache->count_since_key_frame < cache->kmax);
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cache->flush_count = cache->count;
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} else { // Analyze size difference of the two variants.
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const int64_t curr_delta = KeyFramePenalty(encoded_frame);
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if (curr_delta <= cache->best_delta) { // Pick this as keyframe.
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cache->keyframe = index;
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cache->best_delta = curr_delta;
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cache->flush_count = cache->count - 1; // We can flush previous frames.
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}
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if (cache->count_since_key_frame == cache->kmax) {
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cache->flush_count = cache->count;
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cache->count_since_key_frame = 0;
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}
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}
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}
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return 1;
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}
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WebPMuxError WebPFrameCacheFlush(WebPFrameCache* const cache, int verbose,
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WebPMux* const mux) {
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while (cache->flush_count > 0) {
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WebPMuxFrameInfo* info;
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WebPMuxError err;
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EncodedFrame* const curr = CacheGetFrame(cache, 0);
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// Pick frame or full canvas.
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if (cache->keyframe == 0) {
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info = &curr->key_frame;
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info->blend_method = WEBP_MUX_NO_BLEND;
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cache->keyframe = KEYFRAME_NONE;
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cache->best_delta = DELTA_INFINITY;
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} else {
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info = &curr->sub_frame;
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info->blend_method = WEBP_MUX_BLEND;
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}
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// Add to mux.
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err = WebPMuxPushFrame(mux, info, 1);
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if (err != WEBP_MUX_OK) return err;
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if (verbose) {
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printf("Added frame. offset:%d,%d duration:%d dispose:%d blend:%d\n",
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info->x_offset, info->y_offset, info->duration,
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info->dispose_method, info->blend_method);
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}
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FrameRelease(curr);
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++cache->start;
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--cache->flush_count;
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--cache->count;
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if (cache->keyframe != KEYFRAME_NONE) --cache->keyframe;
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}
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if (cache->count == 0) CacheReset(cache);
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return WEBP_MUX_OK;
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}
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WebPMuxError WebPFrameCacheFlushAll(WebPFrameCache* const cache, int verbose,
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WebPMux* const mux) {
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cache->flush_count = cache->count; // Force flushing of all frames.
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return WebPFrameCacheFlush(cache, verbose, mux);
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}
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int WebPFrameCacheShouldTryKeyFrame(const WebPFrameCache* const cache) {
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return cache->count_since_key_frame >= cache->kmin;
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}
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//------------------------------------------------------------------------------
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// Frame rectangle and related utilities.
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static void ClearRectangle(WebPPicture* const picture,
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int left, int top, int width, int height) {
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int j;
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for (j = top; j < top + height; ++j) {
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uint32_t* const dst = picture->argb + j * picture->argb_stride;
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int i;
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for (i = left; i < left + width; ++i) {
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dst[i] = TRANSPARENT_COLOR;
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}
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}
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}
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// Clear pixels in 'picture' within given 'rect' to transparent color.
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void WebPUtilClearPic(WebPPicture* const picture,
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const WebPFrameRect* const rect) {
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if (rect != NULL) {
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ClearRectangle(picture, rect->x_offset, rect->y_offset,
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rect->width, rect->height);
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} else {
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ClearRectangle(picture, 0, 0, picture->width, picture->height);
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}
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}
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// TODO: Also used in picture.c. Move to a common location?
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// Copy width x height pixels from 'src' to 'dst' honoring the strides.
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static void CopyPlane(const uint8_t* src, int src_stride,
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uint8_t* dst, int dst_stride, int width, int height) {
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while (height-- > 0) {
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memcpy(dst, src, width);
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src += src_stride;
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dst += dst_stride;
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}
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}
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void WebPUtilCopyPixels(const WebPPicture* const src, WebPPicture* const dst) {
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assert(src->width == dst->width && src->height == dst->height);
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CopyPlane((uint8_t*)src->argb, 4 * src->argb_stride, (uint8_t*)dst->argb,
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4 * dst->argb_stride, 4 * src->width, src->height);
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}
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void WebPUtilBlendPixels(const WebPPicture* const src,
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const WebPFrameRect* const rect,
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WebPPicture* const dst) {
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int j;
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assert(src->width == dst->width && src->height == dst->height);
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for (j = rect->y_offset; j < rect->y_offset + rect->height; ++j) {
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int i;
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for (i = rect->x_offset; i < rect->x_offset + rect->width; ++i) {
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const uint32_t src_pixel = src->argb[j * src->argb_stride + i];
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const int src_alpha = src_pixel >> 24;
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if (src_alpha != 0) {
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dst->argb[j * dst->argb_stride + i] = src_pixel;
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}
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}
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}
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}
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//------------------------------------------------------------------------------
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// Key frame related utilities.
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int WebPUtilIsKeyFrame(const WebPPicture* const curr,
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const WebPFrameRect* const curr_rect,
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const WebPPicture* const prev) {
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int i, j;
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int is_key_frame = 1;
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// If previous canvas (with previous frame disposed) is all transparent,
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// current frame is a key frame.
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for (i = 0; i < prev->width; ++i) {
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for (j = 0; j < prev->height; ++j) {
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const uint32_t prev_alpha = (prev->argb[j * prev->argb_stride + i]) >> 24;
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if (prev_alpha != 0) {
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is_key_frame = 0;
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break;
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}
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}
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if (!is_key_frame) break;
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}
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if (is_key_frame) return 1;
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// If current frame covers the whole canvas and does not contain any
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// transparent pixels that depend on previous canvas, then current frame is
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// a key frame.
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if (curr_rect->width == curr->width && curr_rect->height == curr->height) {
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assert(curr_rect->x_offset == 0 && curr_rect->y_offset == 0);
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is_key_frame = 1;
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for (j = 0; j < prev->height; ++j) {
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for (i = 0; i < prev->width; ++i) {
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const uint32_t prev_alpha =
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(prev->argb[j * prev->argb_stride + i]) >> 24;
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const uint32_t curr_alpha =
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(curr->argb[j * curr->argb_stride + i]) >> 24;
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if (curr_alpha != 0xff && prev_alpha != 0) {
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is_key_frame = 0;
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break;
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}
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}
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if (!is_key_frame) break;
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}
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if (is_key_frame) return 1;
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}
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return 0;
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}
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void WebPUtilConvertToKeyFrame(const WebPPicture* const prev,
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WebPFrameRect* const rect,
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WebPPicture* const curr) {
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int j;
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assert(curr->width == prev->width && curr->height == prev->height);
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// Replace transparent pixels of current canvas with those from previous
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// canvas (with previous frame disposed).
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for (j = 0; j < curr->height; ++j) {
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int i;
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for (i = 0; i < curr->width; ++i) {
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uint32_t* const curr_pixel = curr->argb + j * curr->argb_stride + i;
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const int curr_alpha = *curr_pixel >> 24;
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if (curr_alpha == 0) {
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*curr_pixel = prev->argb[j * prev->argb_stride + i];
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}
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}
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}
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// Frame rectangle now covers the whole canvas.
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rect->x_offset = 0;
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rect->y_offset = 0;
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rect->width = curr->width;
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rect->height = curr->height;
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}
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//------------------------------------------------------------------------------
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