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Add support for raw lossless bitstream in decoder.

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Previously, it used to assume any raw bitstream is a VP8 one.

Also,
- Factor out VP8CheckSignature() & VP8LCheckSignature().
- Use a local var for *data_ptr in ParseVP8Header() for
readability.

Change-Id: I0fa8aa177dad7865e00c8898f7e7ce76a9db19d5
This commit is contained in:
Urvang Joshi
2012-05-31 11:16:32 +05:30
parent 7cbee29afa
commit 9ef3228301
5 changed files with 37 additions and 16 deletions
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28
src/dec/webp.c
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@ -187,43 +187,49 @@ static VP8StatusCode ParseOptionalChunks(const uint8_t** data,
}
}
// Validates the VP8 Header ("VP8 nnnn" or "VP8L nnnn") and skips over it.
// Validates the VP8/VP8L Header ("VP8 nnnn" or "VP8L nnnn") and skips over it.
// Returns VP8_STATUS_BITSTREAM_ERROR for invalid (chunk larger than
// riff_size) VP8 header,
// riff_size) VP8/VP8L header,
// VP8_STATUS_NOT_ENOUGH_DATA in case of insufficient data, and
// VP8_STATUS_OK otherwise.
// If a VP8/VP8L chunk is found, chunk_size is set to the total number of bytes
// extracted from the VP8/VP8L chunk header.
// The flag 'is_lossless' is set to 1 in case of VP8L chunk.
static VP8StatusCode ParseVP8Header(const uint8_t** data, size_t* data_size,
// The flag 'is_lossless' is set to 1 in case of VP8L chunk / raw VP8L data.
static VP8StatusCode ParseVP8Header(const uint8_t** data_ptr, size_t* data_size,
size_t riff_size,
size_t* chunk_size, int* is_lossless) {
const int is_vp8 = !memcmp(*data, "VP8 ", TAG_SIZE);
const int is_vp8l = !memcmp(*data, "VP8L", TAG_SIZE);
const uint8_t* const data = *data_ptr;
const int is_vp8 = !memcmp(data, "VP8 ", TAG_SIZE);
const int is_vp8l = !memcmp(data, "VP8L", TAG_SIZE);
const uint32_t minimal_size =
TAG_SIZE + CHUNK_HEADER_SIZE; // "WEBP" + "VP8 nnnn"
TAG_SIZE + CHUNK_HEADER_SIZE; // "WEBP" + "VP8 nnnn" OR
// "WEBP" + "VP8Lnnnn"
assert(data);
assert(data_size);
assert(chunk_size);
assert(is_lossless);
*chunk_size = *data_size; // default: raw data
if (*data_size < CHUNK_HEADER_SIZE) {
return VP8_STATUS_NOT_ENOUGH_DATA; // Insufficient data.
}
if (is_vp8 || is_vp8l) {
const uint32_t size = get_le32(*data + TAG_SIZE);
// Bitstream contains VP8/VP8L header.
const uint32_t size = get_le32(data + TAG_SIZE);
if ((riff_size >= minimal_size) && (size > riff_size - minimal_size)) {
return VP8_STATUS_BITSTREAM_ERROR; // Inconsistent size information.
}
// Skip over CHUNK_HEADER_SIZE bytes from VP8/VP8L Header.
*chunk_size = size;
*data += CHUNK_HEADER_SIZE;
*data_ptr += CHUNK_HEADER_SIZE;
*data_size -= CHUNK_HEADER_SIZE;
*is_lossless = is_vp8l;
} else {
// Raw VP8/VP8L bitstream (no header).
*is_lossless = VP8LCheckSignature(data, *data_size);
*chunk_size = *data_size;
}
return VP8_STATUS_OK;
}