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add lossless incremental decoding support

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* We don't need to change DecodeAlpha, since incremental
decoding is not useful for Alpha (we already decode
progressively along the RGB)
* Similarly, we don't do incremental decoding for level>0 planes:
   the metadata don't turn into visible pixel (only the ones in level0), so...
(No visible speed change)

Change-Id: I2fd4b9ba227561a7dbede647686584b752be7baa
This commit is contained in:
Pascal Massimino
2014-09-24 09:38:52 +02:00
parent d4471637ef
commit f060dfc422
5 changed files with 96 additions and 39 deletions
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24
src/dec/idec.c
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@ -502,7 +502,12 @@ static VP8StatusCode DecodeVP8LHeader(WebPIDecoder* const idec) {
dec->status_ = VP8_STATUS_SUSPENDED;
return ErrorStatusLossless(idec, dec->status_);
}
if (!VP8LDecodeHeader(dec, io)) {
if (dec->status_ == VP8_STATUS_BITSTREAM_ERROR &&
curr_size < idec->chunk_size_) {
dec->status_ = VP8_STATUS_SUSPENDED;
}
return ErrorStatusLossless(idec, dec->status_);
}
// Allocate/verify output buffer now.
@ -521,23 +526,15 @@ static VP8StatusCode DecodeVP8LData(WebPIDecoder* const idec) {
const size_t curr_size = MemDataSize(&idec->mem_);
assert(idec->is_lossless_);
// At present Lossless decoder can't decode image incrementally. So wait till
// all the image data is aggregated before image can be decoded.
if (curr_size < idec->chunk_size_) {
return VP8_STATUS_SUSPENDED;
}
// Switch to incremental decoding if we don't have all the bytes available.
dec->incremental_ = (curr_size < idec->chunk_size_);
if (!VP8LDecodeImage(dec)) {
// The decoding is called after all the data-bytes are aggregated. Change
// the error to VP8_BITSTREAM_ERROR in case lossless decoder fails to decode
// all the pixels (VP8_STATUS_SUSPENDED).
if (dec->status_ == VP8_STATUS_SUSPENDED) {
dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
}
return ErrorStatusLossless(idec, dec->status_);
}
return FinishDecoding(idec);
assert(dec->status_ == VP8_STATUS_OK || dec->status_ == VP8_STATUS_SUSPENDED);
return (dec->status_ == VP8_STATUS_SUSPENDED) ? dec->status_
: FinishDecoding(idec);
}
// Main decoding loop
@ -853,4 +850,3 @@ int WebPISetIOHooks(WebPIDecoder* const idec,
return 1;
}