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Design change in ANMF and FRGM chunks:

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- Make ANMF and FRGM chunks hierarchical so that they encompass all chunks of
  that frame.
- Use this in demuxer: stop parsing a frame if all image data for it isn't
  available yet. Thus, we have a frame-level incremental support; that is,
  all frames that are fully available can be parsed.
- Note: We still keep incremental support for single images - so that they can
  be decoded with incremental decoding.

Change-Id: Id1585b16b06caee1d84009c42a25d2de29fa6135
This commit is contained in:
Urvang Joshi
2012-10-31 17:19:31 -07:00
parent f903cbab9a
commit 81b8a741ed
3 changed files with 141 additions and 53 deletions
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21
src/mux/muxinternal.c
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@ -399,13 +399,32 @@ size_t MuxImageListDiskSize(const WebPMuxImage* wpi_list) {
return size;
}
// Special case as ANMF/FRGM chunk encapsulates other image chunks.
static uint8_t* ChunkEmitSpecial(const WebPChunk* const header,
size_t total_size, uint8_t* dst) {
const size_t header_size = header->data_.size;
const size_t offset_to_next = total_size - CHUNK_HEADER_SIZE;
assert(header->tag_ == kChunks[IDX_ANMF].tag ||
header->tag_ == kChunks[IDX_FRGM].tag);
PutLE32(dst + 0, header->tag_);
PutLE32(dst + TAG_SIZE, (uint32_t)offset_to_next);
assert(header_size == (uint32_t)header_size);
memcpy(dst + CHUNK_HEADER_SIZE, header->data_.bytes, header_size);
if (header_size & 1) {
dst[CHUNK_HEADER_SIZE + header_size] = 0; // Add padding.
}
return dst + ChunkDiskSize(header);
}
uint8_t* MuxImageEmit(const WebPMuxImage* const wpi, uint8_t* dst) {
// Ordering of chunks to be emitted is strictly as follows:
// 1. ANMF/FRGM chunk (if present).
// 2. ALPH chunk (if present).
// 3. VP8/VP8L chunk.
assert(wpi);
if (wpi->header_ != NULL) dst = ChunkEmit(wpi->header_, dst);
if (wpi->header_ != NULL) {
dst = ChunkEmitSpecial(wpi->header_, MuxImageDiskSize(wpi), dst);
}
if (wpi->alpha_ != NULL) dst = ChunkEmit(wpi->alpha_, dst);
if (wpi->img_ != NULL) dst = ChunkEmit(wpi->img_, dst);
return dst;