int VP8DecodeLayer(VP8Decoder* dec)
{
assert(dec);
assert(dec.layer_data_size_ > 0);
(void)dec;
// TODO: handle enhancement layer here.
return 1;
}
//------------------------------------------------------------------------------
// Paragraph 9.6
void VP8ParseQuant(VP8Decoder* dec)
{
VP8BitReader* br = &dec.br_;
int base_q0 = VP8GetValue(br, 7);
int dqy1_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
int dqy2_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
int dqy2_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
int dquv_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
int dquv_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
VP8SegmentHeader* hdr = &dec.segment_hdr_;
int i;
for (i = 0; i < NUM_MB_SEGMENTS; ++i) {
int q;
if (hdr.use_segment_) {
q = hdr.quantizer_[i];
if (!hdr.absolute_delta_) {
q += base_q0;
}
} else {
if (i > 0) {
dec.dqm_[i] = dec.dqm_[0];
continue;
} else {
q = base_q0;
}
}
{
VP8QuantMatrix* m = &dec.dqm_[i];
m.y1_mat_[0] = kDcTable[clip(q + dqy1_dc, 127)];
m.y1_mat_[1] = kAcTable[clip(q + 0, 127)];
m.y2_mat_[0] = kDcTable[clip(q + dqy2_dc, 127)] * 2;
// TODO(skal): make it another table?
m.y2_mat_[1] = kAcTable[clip(q + dqy2_ac, 127)] * 155 / 100;
if (m.y2_mat_[1] < 8) m.y2_mat_[1] = 8;
m.uv_mat_[0] = kDcTable[clip(q + dquv_dc, 117)];
m.uv_mat_[1] = kAcTable[clip(q + dquv_ac, 127)];
}
}
}
int VP8SetError(VP8Decoder* dec, VP8StatusCode error, char * msg) {
dec.status_ = error;
dec.error_msg_ = msg;
dec.ready_ = 0;
return 0;
}
void VP8Delete(VP8Decoder* dec) {
if (dec) {
VP8Clear(dec);
free(dec);
}
}
char* VP8StatusMessage(VP8Decoder* dec) {
if (!dec) return "no object";
if (!dec.error_msg_) return "OK";
return dec.error_msg_;
}
VP8StatusCode VP8Status(VP8Decoder* dec) {
if (!dec) return VP8_STATUS_INVALID_PARAM;
return dec.status_;
}
//------------------------------------------------------------------------------
// VP8Decoder
static void SetOk(VP8Decoder* dec) {
dec.status_ = VP8_STATUS_OK;
dec.error_msg_ = "OK";
}
// Topmost call
int VP8GetHeaders(VP8Decoder* dec, VP8Io* io) {
byte* buf;
uint buf_size;
byte* alpha_data_tmp;
uint alpha_size_tmp;
uint vp8_chunk_size;
uint bytes_skipped;
VP8FrameHeader* frm_hdr;
VP8PictureHeader* pic_hdr;
VP8BitReader* br;
VP8StatusCode status;
if (dec == null) {
return 0;
}
SetOk(dec);
if (io == null) {
return VP8SetError(dec, VP8_STATUS_INVALID_PARAM,
"null VP8Io passed to VP8GetHeaders()");
}
buf = io.data;
buf_size = io.data_size;
// Process Pre-VP8 chunks.
status = WebPParseHeaders(&buf, &buf_size, &vp8_chunk_size, &bytes_skipped,
&alpha_data_tmp, &alpha_size_tmp);
if (status != VP8_STATUS_OK) {
return VP8SetError(dec, status, "Incorrect/incomplete header.");
}
if (dec.alpha_data_ == null) {
assert(dec.alpha_data_size_ == 0);
// We have NOT set alpha data yet. Set it now.
// (This is to ensure that dec.alpha_data_ is NOT reset to null if
// WebPParseHeaders() is called more than once, as in incremental decoding
// case.)
dec.alpha_data_ = alpha_data_tmp;
dec.alpha_data_size_ = alpha_size_tmp;
}
// Process the VP8 frame header.
if (buf_size < 4) {
return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
"Truncated header.");
}
// Paragraph 9.1
{
uint bits = buf[0] | (buf[1] << 8) | (buf[2] << 16);
frm_hdr = &dec.frm_hdr_;
frm_hdr.key_frame_ = !(bits & 1);
frm_hdr.profile_ = (bits >> 1) & 7;
frm_hdr.show_ = (bits >> 4) & 1;
frm_hdr.partition_length_ = (bits >> 5);
if (frm_hdr.profile_ > 3)
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"Incorrect keyframe parameters.");
if (!frm_hdr.show_)
return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE,
"Frame not displayable.");
buf += 3;
buf_size -= 3;
}
pic_hdr = &dec.pic_hdr_;
if (frm_hdr.key_frame_) {
// Paragraph 9.2
if (buf_size < 7) {
return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
"cannot parse picture header");
}
if (buf[0] != 0x9d || buf[1] != 0x01 || buf[2] != 0x2a) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"Bad code word");
}
pic_hdr.width_ = ((buf[4] << 8) | buf[3]) & 0x3fff;
pic_hdr.xscale_ = buf[4] >> 6; // ratio: 1, 5/4 5/3 or 2
pic_hdr.height_ = ((buf[6] << 8) | buf[5]) & 0x3fff;
pic_hdr.yscale_ = buf[6] >> 6;
buf += 7;
buf_size -= 7;
dec.mb_w_ = (pic_hdr.width_ + 15) >> 4;
dec.mb_h_ = (pic_hdr.height_ + 15) >> 4;
// Setup default output area (can be later modified during io.setup())
io.width = pic_hdr.width_;
io.height = pic_hdr.height_;
io.use_scaling = 0;
io.use_cropping = 0;
io.crop_top = 0;
io.crop_left = 0;
io.crop_right = io.width;
io.crop_bottom = io.height;
io.mb_w = io.width; // sanity check
io.mb_h = io.height; // ditto
VP8ResetProba(&dec.proba_);
ResetSegmentHeader(&dec.segment_hdr_);
dec.segment_ = 0; // default for intra
}
// Check if we have all the partition #0 available, and initialize dec.br_
// to read this partition (and this partition only).
if (frm_hdr.partition_length_ > buf_size) {
return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
"bad partition length");
}
br = &dec.br_;
VP8InitBitReader(br, buf, buf + frm_hdr.partition_length_);
buf += frm_hdr.partition_length_;
buf_size -= frm_hdr.partition_length_;
if (frm_hdr.key_frame_) {
pic_hdr.colorspace_ = VP8Get(br);
pic_hdr.clamp_type_ = VP8Get(br);
}
if (!ParseSegmentHeader(br, &dec.segment_hdr_, &dec.proba_)) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"cannot parse segment header");
}
// Filter specs
if (!ParseFilterHeader(br, dec)) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"cannot parse filter header");
}
status = ParsePartitions(dec, buf, buf_size);
if (status != VP8_STATUS_OK) {
return VP8SetError(dec, status, "cannot parse partitions");
}
// quantizer change
VP8ParseQuant(dec);
// Frame buffer marking
if (!frm_hdr.key_frame_) {
// Paragraph 9.7
#if !ONLY_KEYFRAME_CODE
dec.buffer_flags_ = VP8Get(br) << 0; // update golden
dec.buffer_flags_ |= VP8Get(br) << 1; // update alt ref
if (!(dec.buffer_flags_ & 1)) {
dec.buffer_flags_ |= VP8GetValue(br, 2) << 2;
}
if (!(dec.buffer_flags_ & 2)) {
dec.buffer_flags_ |= VP8GetValue(br, 2) << 4;
}
dec.buffer_flags_ |= VP8Get(br) << 6; // sign bias golden
dec.buffer_flags_ |= VP8Get(br) << 7; // sign bias alt ref
#else
return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE,
"Not a key frame.");
#endif
} else {
dec.buffer_flags_ = 0x003 | 0x100;
}
// Paragraph 9.8
#if !ONLY_KEYFRAME_CODE
dec.update_proba_ = VP8Get(br);
if (!dec.update_proba_) { // save for later restore
dec.proba_saved_ = dec.proba_;
}
dec.buffer_flags_ &= 1 << 8;
dec.buffer_flags_ |=
(frm_hdr.key_frame_ || VP8Get(br)) << 8; // refresh last frame
#else
VP8Get(br); // just ignore the value of update_proba_
#endif
VP8ParseProba(br, dec);
#if WEBP_EXPERIMENTAL_FEATURES
// Extensions
if (dec.pic_hdr_.colorspace_) {
uint kTrailerSize = 8;
byte kTrailerMarker = 0x01;
byte* ext_buf = buf - kTrailerSize;
uint size;
if (frm_hdr.partition_length_ < kTrailerSize ||
ext_buf[kTrailerSize - 1] != kTrailerMarker) {
return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
"RIFF: Inconsistent extra information.");
}
// Layer
size = (ext_buf[0] << 0) | (ext_buf[1] << 8) | (ext_buf[2] << 16);
dec.layer_data_size_ = size;
dec.layer_data_ = null; // will be set later
dec.layer_colorspace_ = ext_buf[3];
}
#endif
// sanitized state
dec.ready_ = 1;
return 1;
}
// Paragraph 9.4
static int ParseFilterHeader(VP8BitReader* br, VP8Decoder* dec) {
VP8FilterHeader* hdr = &dec.filter_hdr_;
hdr.simple_ = VP8Get(br);
hdr.level_ = VP8GetValue(br, 6);
hdr.sharpness_ = VP8GetValue(br, 3);
hdr.use_lf_delta_ = VP8Get(br);
if (hdr.use_lf_delta_) {
if (VP8Get(br)) { // update lf-delta?
int i;
for (i = 0; i < NUM_REF_LF_DELTAS; ++i) {
if (VP8Get(br)) {
hdr.ref_lf_delta_[i] = VP8GetSignedValue(br, 6);
}
}
for (i = 0; i < NUM_MODE_LF_DELTAS; ++i) {
if (VP8Get(br)) {
hdr.mode_lf_delta_[i] = VP8GetSignedValue(br, 6);
}
}
}
}
dec.filter_type_ = (hdr.level_ == 0) ? 0 : hdr.simple_ ? 1 : 2;
if (dec.filter_type_ > 0) { // precompute filter levels per segment
if (dec.segment_hdr_.use_segment_) {
int s;
for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
int strength = dec.segment_hdr_.filter_strength_[s];
if (!dec.segment_hdr_.absolute_delta_) {
strength += hdr.level_;
}
dec.filter_levels_[s] = strength;
}
} else {
dec.filter_levels_[0] = hdr.level_;
}
}
return !br.eof_;
}
// Paragraph 9.5
// This function returns VP8_STATUS_SUSPENDED if we don't have all the
// necessary data in 'buf'.
// This case is not necessarily an error (for incremental decoding).
// Still, no bitreader is ever initialized to make it possible to read
// unavailable memory.
// If we don't even have the partitions' sizes, than VP8_STATUS_NOT_ENOUGH_DATA
// is returned, and this is an unrecoverable error.
// If the partitions were positioned ok, VP8_STATUS_OK is returned.
static VP8StatusCode ParsePartitions(VP8Decoder* dec,
byte* buf, uint size) {
VP8BitReader* br = &dec.br_;
byte* sz = buf;
byte* buf_end = buf + size;
byte* part_start;
int last_part;
int p;
dec.num_parts_ = 1 << VP8GetValue(br, 2);
last_part = dec.num_parts_ - 1;
part_start = buf + last_part * 3;
if (buf_end < part_start) {
// we can't even read the sizes with sz[]! That's a failure.
return VP8_STATUS_NOT_ENOUGH_DATA;
}
for (p = 0; p < last_part; ++p) {
uint psize = sz[0] | (sz[1] << 8) | (sz[2] << 16);
byte* part_end = part_start + psize;
if (part_end > buf_end) part_end = buf_end;
VP8InitBitReader(dec.parts_ + p, part_start, part_end);
part_start = part_end;
sz += 3;
}
VP8InitBitReader(dec.parts_ + last_part, part_start, buf_end);
return (part_start < buf_end) ? VP8_STATUS_OK :
VP8_STATUS_SUSPENDED; // Init is ok, but there's not enough data
}