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parse one row of intra modes altogether

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(instead of per-macroblock)

speed unchanged.
simplified the context-saving for incremental decoding

Change-Id: I301be581bab581ff68de14c4ffe5bc0ec63f34be
This commit is contained in:
skal
2014-01-28 21:40:40 +01:00
parent a2f608f9e0
commit bbc23ff34c
4 changed files with 55 additions and 48 deletions
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43
src/dec/idec.c
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@ -72,15 +72,14 @@ struct WebPIDecoder {
MemBuffer mem_; // input memory buffer.
WebPDecBuffer output_; // output buffer (when no external one is supplied)
size_t chunk_size_; // Compressed VP8/VP8L size extracted from Header.
int last_mb_y_; // last row reached for intra-mode decoding
};
// MB context to restore in case VP8DecodeMB() fails
typedef struct {
VP8MB left_;
VP8MB info_;
uint8_t intra_t_[4];
uint8_t intra_l_[4];
VP8BitReader br_;
VP8BitReader token_br_;
} MBContext;
@ -264,30 +263,16 @@ static VP8StatusCode FinishDecoding(WebPIDecoder* const idec) {
static void SaveContext(const VP8Decoder* dec, const VP8BitReader* token_br,
MBContext* const context) {
const VP8BitReader* const br = &dec->br_;
const VP8MB* const left = dec->mb_info_ - 1;
const VP8MB* const info = dec->mb_info_ + dec->mb_x_;
context->left_ = *left;
context->info_ = *info;
context->br_ = *br;
context->left_ = dec->mb_info_[-1];
context->info_ = dec->mb_info_[dec->mb_x_];
context->token_br_ = *token_br;
memcpy(context->intra_t_, dec->intra_t_ + 4 * dec->mb_x_, 4);
memcpy(context->intra_l_, dec->intra_l_, 4);
}
static void RestoreContext(const MBContext* context, VP8Decoder* const dec,
VP8BitReader* const token_br) {
VP8BitReader* const br = &dec->br_;
VP8MB* const left = dec->mb_info_ - 1;
VP8MB* const info = dec->mb_info_ + dec->mb_x_;
*left = context->left_;
*info = context->info_;
*br = context->br_;
dec->mb_info_[-1] = context->left_;
dec->mb_info_[dec->mb_x_] = context->info_;
*token_br = context->token_br_;
memcpy(dec->intra_t_ + 4 * dec->mb_x_, context->intra_t_, 4);
memcpy(dec->intra_l_, context->intra_l_, 4);
}
//------------------------------------------------------------------------------
@ -459,16 +444,26 @@ static VP8StatusCode DecodeRemaining(WebPIDecoder* const idec) {
assert(dec->ready_);
for (; dec->mb_y_ < dec->mb_h_; ++dec->mb_y_) {
VP8BitReader* token_br = &dec->parts_[dec->mb_y_ & (dec->num_parts_ - 1)];
if (idec->last_mb_y_ != dec->mb_y_) {
if (!VP8ParseIntraModeRow(&dec->br_, dec)) {
// note: normally, error shouldn't occur since we already have the whole
// partition0 available here in DecodeRemaining(). Reaching EOF while
// reading intra modes really means a BITSTREAM_ERROR.
return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
}
idec->last_mb_y_ = dec->mb_y_;
}
for (; dec->mb_x_ < dec->mb_w_; ++dec->mb_x_) {
VP8BitReader* const token_br =
&dec->parts_[dec->mb_y_ & (dec->num_parts_ - 1)];
MBContext context;
SaveContext(dec, token_br, &context);
if (!VP8DecodeMB(dec, token_br)) {
RestoreContext(&context, dec, token_br);
// We shouldn't fail when MAX_MB data was available
if (dec->num_parts_ == 1 && MemDataSize(&idec->mem_) > MAX_MB_SIZE) {
return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
}
RestoreContext(&context, dec, token_br);
return VP8_STATUS_SUSPENDED;
}
// Release buffer only if there is only one partition
@ -585,6 +580,8 @@ WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer) {
idec->state_ = STATE_WEBP_HEADER;
idec->chunk_size_ = 0;
idec->last_mb_y_ = -1;
InitMemBuffer(&idec->mem_);
WebPInitDecBuffer(&idec->output_);
VP8InitIo(&idec->io_);