1// Copyright 2010 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// main entry for the decoder
11//
12// Author: Skal (pascal.massimino@gmail.com)
13
14#include <stdlib.h>
15
16#include "./alphai_dec.h"
17#include "./vp8i_dec.h"
18#include "./vp8li_dec.h"
19#include "./webpi_dec.h"
20#include "../utils/bit_reader_inl_utils.h"
21#include "../utils/utils.h"
22
23//------------------------------------------------------------------------------
24
25int WebPGetDecoderVersion(void) {
26 return (DEC_MAJ_VERSION << 16) | (DEC_MIN_VERSION << 8) | DEC_REV_VERSION;
27}
28
29//------------------------------------------------------------------------------
30// Signature and pointer-to-function for GetCoeffs() variants below.
31
32typedef int (*GetCoeffsFunc)(VP8BitReader* const br,
33 const VP8BandProbas* const prob[],
34 int ctx, const quant_t dq, int n, int16_t* out);
35static volatile GetCoeffsFunc GetCoeffs = NULL;
36
37static void InitGetCoeffs(void);
38
39//------------------------------------------------------------------------------
40// VP8Decoder
41
42static void SetOk(VP8Decoder* const dec) {
43 dec->status_ = VP8_STATUS_OK;
44 dec->error_msg_ = "OK";
45}
46
47int VP8InitIoInternal(VP8Io* const io, int version) {
48 if (WEBP_ABI_IS_INCOMPATIBLE(version, WEBP_DECODER_ABI_VERSION)) {
49 return 0; // mismatch error
50 }
51 if (io != NULL) {
52 memset(io, 0, sizeof(*io));
53 }
54 return 1;
55}
56
57VP8Decoder* VP8New(void) {
58 VP8Decoder* const dec = (VP8Decoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
59 if (dec != NULL) {
60 SetOk(dec);
61 WebPGetWorkerInterface()->Init(&dec->worker_);
62 dec->ready_ = 0;
63 dec->num_parts_minus_one_ = 0;
64 InitGetCoeffs();
65 }
66 return dec;
67}
68
69VP8StatusCode VP8Status(VP8Decoder* const dec) {
70 if (!dec) return VP8_STATUS_INVALID_PARAM;
71 return dec->status_;
72}
73
74const char* VP8StatusMessage(VP8Decoder* const dec) {
75 if (dec == NULL) return "no object";
76 if (!dec->error_msg_) return "OK";
77 return dec->error_msg_;
78}
79
80void VP8Delete(VP8Decoder* const dec) {
81 if (dec != NULL) {
82 VP8Clear(dec);
83 WebPSafeFree(dec);
84 }
85}
86
87int VP8SetError(VP8Decoder* const dec,
88 VP8StatusCode error, const char* const msg) {
89 // The oldest error reported takes precedence over the new one.
90 if (dec->status_ == VP8_STATUS_OK) {
91 dec->status_ = error;
92 dec->error_msg_ = msg;
93 dec->ready_ = 0;
94 }
95 return 0;
96}
97
98//------------------------------------------------------------------------------
99
100int VP8CheckSignature(const uint8_t* const data, size_t data_size) {
101 return (data_size >= 3 &&
102 data[0] == 0x9d && data[1] == 0x01 && data[2] == 0x2a);
103}
104
105int VP8GetInfo(const uint8_t* data, size_t data_size, size_t chunk_size,
106 int* const width, int* const height) {
107 if (data == NULL || data_size < VP8_FRAME_HEADER_SIZE) {
108 return 0; // not enough data
109 }
110 // check signature
111 if (!VP8CheckSignature(data + 3, data_size - 3)) {
112 return 0; // Wrong signature.
113 } else {
114 const uint32_t bits = data[0] | (data[1] << 8) | (data[2] << 16);
115 const int key_frame = !(bits & 1);
116 const int w = ((data[7] << 8) | data[6]) & 0x3fff;
117 const int h = ((data[9] << 8) | data[8]) & 0x3fff;
118
119 if (!key_frame) { // Not a keyframe.
120 return 0;
121 }
122
123 if (((bits >> 1) & 7) > 3) {
124 return 0; // unknown profile
125 }
126 if (!((bits >> 4) & 1)) {
127 return 0; // first frame is invisible!
128 }
129 if (((bits >> 5)) >= chunk_size) { // partition_length
130 return 0; // inconsistent size information.
131 }
132 if (w == 0 || h == 0) {
133 return 0; // We don't support both width and height to be zero.
134 }
135
136 if (width) {
137 *width = w;
138 }
139 if (height) {
140 *height = h;
141 }
142
143 return 1;
144 }
145}
146
147//------------------------------------------------------------------------------
148// Header parsing
149
150static void ResetSegmentHeader(VP8SegmentHeader* const hdr) {
151 assert(hdr != NULL);
152 hdr->use_segment_ = 0;
153 hdr->update_map_ = 0;
154 hdr->absolute_delta_ = 1;
155 memset(hdr->quantizer_, 0, sizeof(hdr->quantizer_));
156 memset(hdr->filter_strength_, 0, sizeof(hdr->filter_strength_));
157}
158
159// Paragraph 9.3
160static int ParseSegmentHeader(VP8BitReader* br,
161 VP8SegmentHeader* hdr, VP8Proba* proba) {
162 assert(br != NULL);
163 assert(hdr != NULL);
164 hdr->use_segment_ = VP8Get(br);
165 if (hdr->use_segment_) {
166 hdr->update_map_ = VP8Get(br);
167 if (VP8Get(br)) { // update data
168 int s;
169 hdr->absolute_delta_ = VP8Get(br);
170 for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
171 hdr->quantizer_[s] = VP8Get(br) ? VP8GetSignedValue(br, 7) : 0;
172 }
173 for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
174 hdr->filter_strength_[s] = VP8Get(br) ? VP8GetSignedValue(br, 6) : 0;
175 }
176 }
177 if (hdr->update_map_) {
178 int s;
179 for (s = 0; s < MB_FEATURE_TREE_PROBS; ++s) {
180 proba->segments_[s] = VP8Get(br) ? VP8GetValue(br, 8) : 255u;
181 }
182 }
183 } else {
184 hdr->update_map_ = 0;
185 }
186 return !br->eof_;
187}
188
189// Paragraph 9.5
190// This function returns VP8_STATUS_SUSPENDED if we don't have all the
191// necessary data in 'buf'.
192// This case is not necessarily an error (for incremental decoding).
193// Still, no bitreader is ever initialized to make it possible to read
194// unavailable memory.
195// If we don't even have the partitions' sizes, than VP8_STATUS_NOT_ENOUGH_DATA
196// is returned, and this is an unrecoverable error.
197// If the partitions were positioned ok, VP8_STATUS_OK is returned.
198static VP8StatusCode ParsePartitions(VP8Decoder* const dec,
199 const uint8_t* buf, size_t size) {
200 VP8BitReader* const br = &dec->br_;
201 const uint8_t* sz = buf;
202 const uint8_t* buf_end = buf + size;
203 const uint8_t* part_start;
204 size_t size_left = size;
205 size_t last_part;
206 size_t p;
207
208 dec->num_parts_minus_one_ = (1 << VP8GetValue(br, 2)) - 1;
209 last_part = dec->num_parts_minus_one_;
210 if (size < 3 * last_part) {
211 // we can't even read the sizes with sz[]! That's a failure.
212 return VP8_STATUS_NOT_ENOUGH_DATA;
213 }
214 part_start = buf + last_part * 3;
215 size_left -= last_part * 3;
216 for (p = 0; p < last_part; ++p) {
217 size_t psize = sz[0] | (sz[1] << 8) | (sz[2] << 16);
218 if (psize > size_left) psize = size_left;
219 VP8InitBitReader(dec->parts_ + p, part_start, psize);
220 part_start += psize;
221 size_left -= psize;
222 sz += 3;
223 }
224 VP8InitBitReader(dec->parts_ + last_part, part_start, size_left);
225 return (part_start < buf_end) ? VP8_STATUS_OK :
226 VP8_STATUS_SUSPENDED; // Init is ok, but there's not enough data
227}
228
229// Paragraph 9.4
230static int ParseFilterHeader(VP8BitReader* br, VP8Decoder* const dec) {
231 VP8FilterHeader* const hdr = &dec->filter_hdr_;
232 hdr->simple_ = VP8Get(br);
233 hdr->level_ = VP8GetValue(br, 6);
234 hdr->sharpness_ = VP8GetValue(br, 3);
235 hdr->use_lf_delta_ = VP8Get(br);
236 if (hdr->use_lf_delta_) {
237 if (VP8Get(br)) { // update lf-delta?
238 int i;
239 for (i = 0; i < NUM_REF_LF_DELTAS; ++i) {
240 if (VP8Get(br)) {
241 hdr->ref_lf_delta_[i] = VP8GetSignedValue(br, 6);
242 }
243 }
244 for (i = 0; i < NUM_MODE_LF_DELTAS; ++i) {
245 if (VP8Get(br)) {
246 hdr->mode_lf_delta_[i] = VP8GetSignedValue(br, 6);
247 }
248 }
249 }
250 }
251 dec->filter_type_ = (hdr->level_ == 0) ? 0 : hdr->simple_ ? 1 : 2;
252 return !br->eof_;
253}
254
255// Topmost call
256int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
257 const uint8_t* buf;
258 size_t buf_size;
259 VP8FrameHeader* frm_hdr;
260 VP8PictureHeader* pic_hdr;
261 VP8BitReader* br;
262 VP8StatusCode status;
263
264 if (dec == NULL) {
265 return 0;
266 }
267 SetOk(dec);
268 if (io == NULL) {
269 return VP8SetError(dec, VP8_STATUS_INVALID_PARAM,
270 "null VP8Io passed to VP8GetHeaders()");
271 }
272 buf = io->data;
273 buf_size = io->data_size;
274 if (buf_size < 4) {
275 return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
276 "Truncated header.");
277 }
278
279 // Paragraph 9.1
280 {
281 const uint32_t bits = buf[0] | (buf[1] << 8) | (buf[2] << 16);
282 frm_hdr = &dec->frm_hdr_;
283 frm_hdr->key_frame_ = !(bits & 1);
284 frm_hdr->profile_ = (bits >> 1) & 7;
285 frm_hdr->show_ = (bits >> 4) & 1;
286 frm_hdr->partition_length_ = (bits >> 5);
287 if (frm_hdr->profile_ > 3) {
288 return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
289 "Incorrect keyframe parameters.");
290 }
291 if (!frm_hdr->show_) {
292 return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE,
293 "Frame not displayable.");
294 }
295 buf += 3;
296 buf_size -= 3;
297 }
298
299 pic_hdr = &dec->pic_hdr_;
300 if (frm_hdr->key_frame_) {
301 // Paragraph 9.2
302 if (buf_size < 7) {
303 return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
304 "cannot parse picture header");
305 }
306 if (!VP8CheckSignature(buf, buf_size)) {
307 return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
308 "Bad code word");
309 }
310 pic_hdr->width_ = ((buf[4] << 8) | buf[3]) & 0x3fff;
311 pic_hdr->xscale_ = buf[4] >> 6; // ratio: 1, 5/4 5/3 or 2
312 pic_hdr->height_ = ((buf[6] << 8) | buf[5]) & 0x3fff;
313 pic_hdr->yscale_ = buf[6] >> 6;
314 buf += 7;
315 buf_size -= 7;
316
317 dec->mb_w_ = (pic_hdr->width_ + 15) >> 4;
318 dec->mb_h_ = (pic_hdr->height_ + 15) >> 4;
319
320 // Setup default output area (can be later modified during io->setup())
321 io->width = pic_hdr->width_;
322 io->height = pic_hdr->height_;
323 // IMPORTANT! use some sane dimensions in crop_* and scaled_* fields.
324 // So they can be used interchangeably without always testing for
325 // 'use_cropping'.
326 io->use_cropping = 0;
327 io->crop_top = 0;
328 io->crop_left = 0;
329 io->crop_right = io->width;
330 io->crop_bottom = io->height;
331 io->use_scaling = 0;
332 io->scaled_width = io->width;
333 io->scaled_height = io->height;
334
335 io->mb_w = io->width; // sanity check
336 io->mb_h = io->height; // ditto
337
338 VP8ResetProba(&dec->proba_);
339 ResetSegmentHeader(&dec->segment_hdr_);
340 }
341
342 // Check if we have all the partition #0 available, and initialize dec->br_
343 // to read this partition (and this partition only).
344 if (frm_hdr->partition_length_ > buf_size) {
345 return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
346 "bad partition length");
347 }
348
349 br = &dec->br_;
350 VP8InitBitReader(br, buf, frm_hdr->partition_length_);
351 buf += frm_hdr->partition_length_;
352 buf_size -= frm_hdr->partition_length_;
353
354 if (frm_hdr->key_frame_) {
355 pic_hdr->colorspace_ = VP8Get(br);
356 pic_hdr->clamp_type_ = VP8Get(br);
357 }
358 if (!ParseSegmentHeader(br, &dec->segment_hdr_, &dec->proba_)) {
359 return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
360 "cannot parse segment header");
361 }
362 // Filter specs
363 if (!ParseFilterHeader(br, dec)) {
364 return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR,
365 "cannot parse filter header");
366 }
367 status = ParsePartitions(dec, buf, buf_size);
368 if (status != VP8_STATUS_OK) {
369 return VP8SetError(dec, status, "cannot parse partitions");
370 }
371
372 // quantizer change
373 VP8ParseQuant(dec);
374
375 // Frame buffer marking
376 if (!frm_hdr->key_frame_) {
377 return VP8SetError(dec, VP8_STATUS_UNSUPPORTED_FEATURE,
378 "Not a key frame.");
379 }
380
381 VP8Get(br); // ignore the value of update_proba_
382
383 VP8ParseProba(br, dec);
384
385 // sanitized state
386 dec->ready_ = 1;
387 return 1;
388}
389
390//------------------------------------------------------------------------------
391// Residual decoding (Paragraph 13.2 / 13.3)
392
393static const uint8_t kCat3[] = { 173, 148, 140, 0 };
394static const uint8_t kCat4[] = { 176, 155, 140, 135, 0 };
395static const uint8_t kCat5[] = { 180, 157, 141, 134, 130, 0 };
396static const uint8_t kCat6[] =
397 { 254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129, 0 };
398static const uint8_t* const kCat3456[] = { kCat3, kCat4, kCat5, kCat6 };
399static const uint8_t kZigzag[16] = {
400 0, 1, 4, 8, 5, 2, 3, 6, 9, 12, 13, 10, 7, 11, 14, 15
401};
402
403// See section 13-2: http://tools.ietf.org/html/rfc6386#section-13.2
404static int GetLargeValue(VP8BitReader* const br, const uint8_t* const p) {
405 int v;
406 if (!VP8GetBit(br, p[3])) {
407 if (!VP8GetBit(br, p[4])) {
408 v = 2;
409 } else {
410 v = 3 + VP8GetBit(br, p[5]);
411 }
412 } else {
413 if (!VP8GetBit(br, p[6])) {
414 if (!VP8GetBit(br, p[7])) {
415 v = 5 + VP8GetBit(br, 159);
416 } else {
417 v = 7 + 2 * VP8GetBit(br, 165);
418 v += VP8GetBit(br, 145);
419 }
420 } else {
421 const uint8_t* tab;
422 const int bit1 = VP8GetBit(br, p[8]);
423 const int bit0 = VP8GetBit(br, p[9 + bit1]);
424 const int cat = 2 * bit1 + bit0;
425 v = 0;
426 for (tab = kCat3456[cat]; *tab; ++tab) {
427 v += v + VP8GetBit(br, *tab);
428 }
429 v += 3 + (8 << cat);
430 }
431 }
432 return v;
433}
434
435// Returns the position of the last non-zero coeff plus one
436static int GetCoeffsFast(VP8BitReader* const br,
437 const VP8BandProbas* const prob[],
438 int ctx, const quant_t dq, int n, int16_t* out) {
439 const uint8_t* p = prob[n]->probas_[ctx];
440 for (; n < 16; ++n) {
441 if (!VP8GetBit(br, p[0])) {
442 return n; // previous coeff was last non-zero coeff
443 }
444 while (!VP8GetBit(br, p[1])) { // sequence of zero coeffs
445 p = prob[++n]->probas_[0];
446 if (n == 16) return 16;
447 }
448 { // non zero coeff
449 const VP8ProbaArray* const p_ctx = &prob[n + 1]->probas_[0];
450 int v;
451 if (!VP8GetBit(br, p[2])) {
452 v = 1;
453 p = p_ctx[1];
454 } else {
455 v = GetLargeValue(br, p);
456 p = p_ctx[2];
457 }
458 out[kZigzag[n]] = VP8GetSigned(br, v) * dq[n > 0];
459 }
460 }
461 return 16;
462}
463
464// This version of GetCoeffs() uses VP8GetBitAlt() which is an alternate version
465// of VP8GetBitAlt() targeting specific platforms.
466static int GetCoeffsAlt(VP8BitReader* const br,
467 const VP8BandProbas* const prob[],
468 int ctx, const quant_t dq, int n, int16_t* out) {
469 const uint8_t* p = prob[n]->probas_[ctx];
470 for (; n < 16; ++n) {
471 if (!VP8GetBitAlt(br, p[0])) {
472 return n; // previous coeff was last non-zero coeff
473 }
474 while (!VP8GetBitAlt(br, p[1])) { // sequence of zero coeffs
475 p = prob[++n]->probas_[0];
476 if (n == 16) return 16;
477 }
478 { // non zero coeff
479 const VP8ProbaArray* const p_ctx = &prob[n + 1]->probas_[0];
480 int v;
481 if (!VP8GetBitAlt(br, p[2])) {
482 v = 1;
483 p = p_ctx[1];
484 } else {
485 v = GetLargeValue(br, p);
486 p = p_ctx[2];
487 }
488 out[kZigzag[n]] = VP8GetSigned(br, v) * dq[n > 0];
489 }
490 }
491 return 16;
492}
493
494WEBP_TSAN_IGNORE_FUNCTION static void InitGetCoeffs(void) {
495 if (GetCoeffs == NULL) {
496 if (VP8GetCPUInfo != NULL && VP8GetCPUInfo(kSlowSSSE3)) {
497 GetCoeffs = GetCoeffsAlt;
498 } else {
499 GetCoeffs = GetCoeffsFast;
500 }
501 }
502}
503
504static WEBP_INLINE uint32_t NzCodeBits(uint32_t nz_coeffs, int nz, int dc_nz) {
505 nz_coeffs <<= 2;
506 nz_coeffs |= (nz > 3) ? 3 : (nz > 1) ? 2 : dc_nz;
507 return nz_coeffs;
508}
509
510static int ParseResiduals(VP8Decoder* const dec,
511 VP8MB* const mb, VP8BitReader* const token_br) {
512 const VP8BandProbas* (* const bands)[16 + 1] = dec->proba_.bands_ptr_;
513 const VP8BandProbas* const * ac_proba;
514 VP8MBData* const block = dec->mb_data_ + dec->mb_x_;
515 const VP8QuantMatrix* const q = &dec->dqm_[block->segment_];
516 int16_t* dst = block->coeffs_;
517 VP8MB* const left_mb = dec->mb_info_ - 1;
518 uint8_t tnz, lnz;
519 uint32_t non_zero_y = 0;
520 uint32_t non_zero_uv = 0;
521 int x, y, ch;
522 uint32_t out_t_nz, out_l_nz;
523 int first;
524
525 memset(dst, 0, 384 * sizeof(*dst));
526 if (!block->is_i4x4_) { // parse DC
527 int16_t dc[16] = { 0 };
528 const int ctx = mb->nz_dc_ + left_mb->nz_dc_;
529 const int nz = GetCoeffs(token_br, bands[1], ctx, q->y2_mat_, 0, dc);
530 mb->nz_dc_ = left_mb->nz_dc_ = (nz > 0);
531 if (nz > 1) { // more than just the DC -> perform the full transform
532 VP8TransformWHT(dc, dst);
533 } else { // only DC is non-zero -> inlined simplified transform
534 int i;
535 const int dc0 = (dc[0] + 3) >> 3;
536 for (i = 0; i < 16 * 16; i += 16) dst[i] = dc0;
537 }
538 first = 1;
539 ac_proba = bands[0];
540 } else {
541 first = 0;
542 ac_proba = bands[3];
543 }
544
545 tnz = mb->nz_ & 0x0f;
546 lnz = left_mb->nz_ & 0x0f;
547 for (y = 0; y < 4; ++y) {
548 int l = lnz & 1;
549 uint32_t nz_coeffs = 0;
550 for (x = 0; x < 4; ++x) {
551 const int ctx = l + (tnz & 1);
552 const int nz = GetCoeffs(token_br, ac_proba, ctx, q->y1_mat_, first, dst);
553 l = (nz > first);
554 tnz = (tnz >> 1) | (l << 7);
555 nz_coeffs = NzCodeBits(nz_coeffs, nz, dst[0] != 0);
556 dst += 16;
557 }
558 tnz >>= 4;
559 lnz = (lnz >> 1) | (l << 7);
560 non_zero_y = (non_zero_y << 8) | nz_coeffs;
561 }
562 out_t_nz = tnz;
563 out_l_nz = lnz >> 4;
564
565 for (ch = 0; ch < 4; ch += 2) {
566 uint32_t nz_coeffs = 0;
567 tnz = mb->nz_ >> (4 + ch);
568 lnz = left_mb->nz_ >> (4 + ch);
569 for (y = 0; y < 2; ++y) {
570 int l = lnz & 1;
571 for (x = 0; x < 2; ++x) {
572 const int ctx = l + (tnz & 1);
573 const int nz = GetCoeffs(token_br, bands[2], ctx, q->uv_mat_, 0, dst);
574 l = (nz > 0);
575 tnz = (tnz >> 1) | (l << 3);
576 nz_coeffs = NzCodeBits(nz_coeffs, nz, dst[0] != 0);
577 dst += 16;
578 }
579 tnz >>= 2;
580 lnz = (lnz >> 1) | (l << 5);
581 }
582 // Note: we don't really need the per-4x4 details for U/V blocks.
583 non_zero_uv |= nz_coeffs << (4 * ch);
584 out_t_nz |= (tnz << 4) << ch;
585 out_l_nz |= (lnz & 0xf0) << ch;
586 }
587 mb->nz_ = out_t_nz;
588 left_mb->nz_ = out_l_nz;
589
590 block->non_zero_y_ = non_zero_y;
591 block->non_zero_uv_ = non_zero_uv;
592
593 // We look at the mode-code of each block and check if some blocks have less
594 // than three non-zero coeffs (code < 2). This is to avoid dithering flat and
595 // empty blocks.
596 block->dither_ = (non_zero_uv & 0xaaaa) ? 0 : q->dither_;
597
598 return !(non_zero_y | non_zero_uv); // will be used for further optimization
599}
600
601//------------------------------------------------------------------------------
602// Main loop
603
604int VP8DecodeMB(VP8Decoder* const dec, VP8BitReader* const token_br) {
605 VP8MB* const left = dec->mb_info_ - 1;
606 VP8MB* const mb = dec->mb_info_ + dec->mb_x_;
607 VP8MBData* const block = dec->mb_data_ + dec->mb_x_;
608 int skip = dec->use_skip_proba_ ? block->skip_ : 0;
609
610 if (!skip) {
611 skip = ParseResiduals(dec, mb, token_br);
612 } else {
613 left->nz_ = mb->nz_ = 0;
614 if (!block->is_i4x4_) {
615 left->nz_dc_ = mb->nz_dc_ = 0;
616 }
617 block->non_zero_y_ = 0;
618 block->non_zero_uv_ = 0;
619 block->dither_ = 0;
620 }
621
622 if (dec->filter_type_ > 0) { // store filter info
623 VP8FInfo* const finfo = dec->f_info_ + dec->mb_x_;
624 *finfo = dec->fstrengths_[block->segment_][block->is_i4x4_];
625 finfo->f_inner_ |= !skip;
626 }
627
628 return !token_br->eof_;
629}
630
631void VP8InitScanline(VP8Decoder* const dec) {
632 VP8MB* const left = dec->mb_info_ - 1;
633 left->nz_ = 0;
634 left->nz_dc_ = 0;
635 memset(dec->intra_l_, B_DC_PRED, sizeof(dec->intra_l_));
636 dec->mb_x_ = 0;
637}
638
639static int ParseFrame(VP8Decoder* const dec, VP8Io* io) {
640 for (dec->mb_y_ = 0; dec->mb_y_ < dec->br_mb_y_; ++dec->mb_y_) {
641 // Parse bitstream for this row.
642 VP8BitReader* const token_br =
643 &dec->parts_[dec->mb_y_ & dec->num_parts_minus_one_];
644 if (!VP8ParseIntraModeRow(&dec->br_, dec)) {
645 return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
646 "Premature end-of-partition0 encountered.");
647 }
648 for (; dec->mb_x_ < dec->mb_w_; ++dec->mb_x_) {
649 if (!VP8DecodeMB(dec, token_br)) {
650 return VP8SetError(dec, VP8_STATUS_NOT_ENOUGH_DATA,
651 "Premature end-of-file encountered.");
652 }
653 }
654 VP8InitScanline(dec); // Prepare for next scanline
655
656 // Reconstruct, filter and emit the row.
657 if (!VP8ProcessRow(dec, io)) {
658 return VP8SetError(dec, VP8_STATUS_USER_ABORT, "Output aborted.");
659 }
660 }
661 if (dec->mt_method_ > 0) {
662 if (!WebPGetWorkerInterface()->Sync(&dec->worker_)) return 0;
663 }
664
665 return 1;
666}
667
668// Main entry point
669int VP8Decode(VP8Decoder* const dec, VP8Io* const io) {
670 int ok = 0;
671 if (dec == NULL) {
672 return 0;
673 }
674 if (io == NULL) {
675 return VP8SetError(dec, VP8_STATUS_INVALID_PARAM,
676 "NULL VP8Io parameter in VP8Decode().");
677 }
678
679 if (!dec->ready_) {
680 if (!VP8GetHeaders(dec, io)) {
681 return 0;
682 }
683 }
684 assert(dec->ready_);
685
686 // Finish setting up the decoding parameter. Will call io->setup().
687 ok = (VP8EnterCritical(dec, io) == VP8_STATUS_OK);
688 if (ok) { // good to go.
689 // Will allocate memory and prepare everything.
690 if (ok) ok = VP8InitFrame(dec, io);
691
692 // Main decoding loop
693 if (ok) ok = ParseFrame(dec, io);
694
695 // Exit.
696 ok &= VP8ExitCritical(dec, io);
697 }
698
699 if (!ok) {
700 VP8Clear(dec);
701 return 0;
702 }
703
704 dec->ready_ = 0;
705 return ok;
706}
707
708void VP8Clear(VP8Decoder* const dec) {
709 if (dec == NULL) {
710 return;
711 }
712 WebPGetWorkerInterface()->End(&dec->worker_);
713 WebPDeallocateAlphaMemory(dec);
714 WebPSafeFree(dec->mem_);
715 dec->mem_ = NULL;
716 dec->mem_size_ = 0;
717 memset(&dec->br_, 0, sizeof(dec->br_));
718 dec->ready_ = 0;
719}
720
721//------------------------------------------------------------------------------
722