FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/mss4.c
Date: 2025-11-04 10:33:36
Exec Total Coverage
Lines: 273 302 90.4%
Functions: 13 13 100.0%
Branches: 162 190 85.3%
Line Branch Exec Source
1 /*
2 * Microsoft Screen 4 (aka Microsoft Expression Encoder Screen) decoder
3 * Copyright (c) 2012 Konstantin Shishkov
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * Microsoft Screen 4 (aka Microsoft Titanium Screen 2,
25 * aka Microsoft Expression Encoder Screen) decoder
26 */
27
28 #include "libavutil/mem.h"
29 #include "libavutil/thread.h"
30 #include "libavutil/imgutils.h"
31
32 #include "avcodec.h"
33 #include "bytestream.h"
34 #include "codec_internal.h"
35 #include "decode.h"
36 #include "get_bits.h"
37 #include "jpegtables.h"
38 #include "mss34dsp.h"
39 #include "unary.h"
40
41 #define HEADER_SIZE 8
42
43 enum FrameType {
44 INTRA_FRAME = 0,
45 INTER_FRAME,
46 SKIP_FRAME
47 };
48
49 enum BlockType {
50 SKIP_BLOCK = 0,
51 DCT_BLOCK,
52 IMAGE_BLOCK,
53 };
54
55 enum CachePos {
56 LEFT = 0,
57 TOP_LEFT,
58 TOP,
59 };
60
61 static const uint8_t mss4_dc_vlc_lens[2][16] = {
62 { 0, 1, 5, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0 },
63 { 0, 3, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0 }
64 };
65
66 static const uint8_t vec_len_syms[2][4] = {
67 { 4, 2, 3, 1 },
68 { 4, 1, 2, 3 }
69 };
70
71 static const uint8_t mss4_vec_entry_vlc_lens[2][16] = {
72 { 0, 2, 2, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
73 { 0, 1, 5, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }
74 };
75
76 static const uint8_t mss4_vec_entry_vlc_syms[2][9] = {
77 { 0, 7, 6, 5, 8, 4, 3, 1, 2 },
78 { 0, 2, 3, 4, 5, 6, 7, 1, 8 }
79 };
80
81 #define MAX_ENTRIES 162
82
83 typedef struct MSS4Context {
84 AVFrame *pic;
85
86 int block[64];
87 uint8_t imgbuf[3][16 * 16];
88
89 int quality;
90 uint16_t quant_mat[2][64];
91
92 int *prev_dc[3];
93 ptrdiff_t dc_stride[3];
94 int dc_cache[4][4];
95
96 int prev_vec[3][4];
97 } MSS4Context;
98
99 static VLC dc_vlc[2], ac_vlc[2];
100 static VLC vec_entry_vlc[2];
101
102 12 static av_cold void mss4_init_vlc(VLC *vlc, unsigned *offset,
103 const uint8_t *lens, const uint8_t *syms)
104 {
105 static VLCElem vlc_buf[2146];
106 uint8_t bits[MAX_ENTRIES];
107 int i, j;
108 12 int idx = 0;
109
110
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 204 for (i = 0; i < 16; i++) {
111
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 924 for (j = 0; j < lens[i]; j++) {
112 732 bits[idx] = i + 1;
113 732 idx++;
114 }
115 }
116
117 12 vlc->table = &vlc_buf[*offset];
118 12 vlc->table_allocated = FF_ARRAY_ELEMS(vlc_buf) - *offset;
119 12 ff_vlc_init_from_lengths(vlc, FFMIN(bits[idx - 1], 9), idx,
120 bits, 1, syms, 1, 1,
121 0, VLC_INIT_STATIC_OVERLONG, NULL);
122 12 *offset += vlc->table_size;
123 12 }
124
125 2 static av_cold void mss4_init_vlcs(void)
126 {
127
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 6 for (unsigned i = 0, offset = 0; i < 2; i++) {
128 4 mss4_init_vlc(&dc_vlc[i], &offset, mss4_dc_vlc_lens[i], NULL);
129
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 4 mss4_init_vlc(&ac_vlc[i], &offset,
130 i ? ff_mjpeg_bits_ac_chrominance + 1
131 : ff_mjpeg_bits_ac_luminance + 1,
132 i ? ff_mjpeg_val_ac_chrominance
133 : ff_mjpeg_val_ac_luminance);
134 4 mss4_init_vlc(&vec_entry_vlc[i], &offset, mss4_vec_entry_vlc_lens[i],
135 4 mss4_vec_entry_vlc_syms[i]);
136 }
137 2 }
138
139 /* This function returns values in the range
140 * (-range + 1; -range/2] U [range/2; range - 1)
141 * i.e.
142 * nbits = 0 -> 0
143 * nbits = 1 -> -1, 1
144 * nbits = 2 -> -3, -2, 2, 3
145 */
146 315916 static av_always_inline int get_coeff_bits(GetBitContext *gb, int nbits)
147 {
148 int val;
149
150
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 315916 if (!nbits)
151 133329 return 0;
152
153 182587 val = get_bits(gb, nbits);
154
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 182587 if (val < (1 << (nbits - 1)))
155 98069 val -= (1 << nbits) - 1;
156
157 182587 return val;
158 }
159
160 180586 static inline int get_coeff(GetBitContext *gb, const VLC *vlc,
161 int nb_bits, int max_depth)
162 {
163 180586 int val = get_vlc2(gb, vlc->table, nb_bits, max_depth);
164
165 180586 return get_coeff_bits(gb, val);
166 }
167
168 85284 static int mss4_decode_dct(GetBitContext *gb, VLC *dc_vlc, VLC *ac_vlc,
169 int *block, int *dc_cache,
170 int bx, int by, uint16_t *quant_mat)
171 {
172 85284 int skip, val, pos = 1, zz_pos, dc;
173
174 85284 memset(block, 0, sizeof(*block) * 64);
175
176 85284 dc = get_coeff(gb, dc_vlc, dc_vlc->bits, 2);
177 // DC prediction is the same as in MSS3
178
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 85284 if (by) {
179
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 84904 if (bx) {
180 int l, tl, t;
181
182 83868 l = dc_cache[LEFT];
183 83868 tl = dc_cache[TOP_LEFT];
184 83868 t = dc_cache[TOP];
185
186
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 83868 if (FFABS(t - tl) <= FFABS(l - tl))
187 80876 dc += l;
188 else
189 2992 dc += t;
190 } else {
191 1036 dc += dc_cache[TOP];
192 }
193
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 380 } else if (bx) {
194 380 dc += dc_cache[LEFT];
195 }
196 85284 dc_cache[LEFT] = dc;
197 85284 block[0] = dc * quant_mat[0];
198
199
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 220682 while (pos < 64) {
200 219785 val = get_vlc2(gb, ac_vlc->table, 9, 2);
201
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 219785 if (!val)
202 84387 return 0;
203
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 135398 if (val == -1)
204 ✗ return -1;
205
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 135398 if (val == 0xF0) {
206 68 pos += 16;
207 68 continue;
208 }
209 135330 skip = val >> 4;
210 135330 val = get_coeff_bits(gb, val & 0xF);
211 135330 pos += skip;
212
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 135330 if (pos >= 64)
213 ✗ return -1;
214
215 135330 zz_pos = ff_zigzag_direct[pos];
216 135330 block[zz_pos] = val * quant_mat[zz_pos];
217 135330 pos++;
218 }
219
220
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 897 return pos == 64 ? 0 : -1;
221 }
222
223 14214 static int mss4_decode_dct_block(MSS4Context *c, GetBitContext *gb,
224 uint8_t *dst[3], int mb_x, int mb_y)
225 {
226 int i, j, k, ret;
227 14214 uint8_t *out = dst[0];
228
229
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 42642 for (j = 0; j < 2; j++) {
230
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 85284 for (i = 0; i < 2; i++) {
231 56856 int xpos = mb_x * 2 + i;
232 56856 c->dc_cache[j][TOP_LEFT] = c->dc_cache[j][TOP];
233 56856 c->dc_cache[j][TOP] = c->prev_dc[0][mb_x * 2 + i];
234 56856 ret = mss4_decode_dct(gb, &dc_vlc[0], &ac_vlc[0], c->block,
235 56856 c->dc_cache[j],
236 56856 xpos, mb_y * 2 + j, c->quant_mat[0]);
237
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 56856 if (ret)
238 ✗ return ret;
239 56856 c->prev_dc[0][mb_x * 2 + i] = c->dc_cache[j][LEFT];
240
241 56856 ff_mss34_dct_put(out + xpos * 8, c->pic->linesize[0],
242 56856 c->block);
243 }
244 28428 out += 8 * c->pic->linesize[0];
245 }
246
247
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 42642 for (i = 1; i < 3; i++) {
248 28428 c->dc_cache[i + 1][TOP_LEFT] = c->dc_cache[i + 1][TOP];
249 28428 c->dc_cache[i + 1][TOP] = c->prev_dc[i][mb_x];
250 28428 ret = mss4_decode_dct(gb, &dc_vlc[1], &ac_vlc[1],
251 28428 c->block, c->dc_cache[i + 1], mb_x, mb_y,
252 28428 c->quant_mat[1]);
253
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 28428 if (ret)
254 ✗ return ret;
255 28428 c->prev_dc[i][mb_x] = c->dc_cache[i + 1][LEFT];
256
257 28428 ff_mss34_dct_put(c->imgbuf[i], 8, c->block);
258 28428 out = dst[i] + mb_x * 16;
259 // Since the DCT block is coded as YUV420 and the whole frame as YUV444,
260 // we need to scale chroma.
261
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 483276 for (j = 0; j < 16; j++) {
262
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 4093632 for (k = 0; k < 8; k++)
263 3638784 AV_WN16A(out + k * 2, c->imgbuf[i][k + (j & ~1) * 4] * 0x101);
264 454848 out += c->pic->linesize[i];
265 }
266 }
267
268 14214 return 0;
269 }
270
271 281245 static void read_vec_pos(GetBitContext *gb, int *vec_pos, int *sel_flag,
272 int *sel_len, int *prev)
273 {
274 281245 int i, y_flag = 0;
275
276
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 1124980 for (i = 2; i >= 0; i--) {
277
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 843735 if (!sel_flag[i]) {
278 192630 vec_pos[i] = 0;
279 192630 continue;
280 }
281
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 651105 if ((!i && !y_flag) || get_bits1(gb)) {
282
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 554066 if (sel_len[i] > 0) {
283 549560 int pval = prev[i];
284 549560 vec_pos[i] = get_bits(gb, sel_len[i]);
285
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 549560 if (vec_pos[i] >= pval)
286 297455 vec_pos[i]++;
287 } else {
288 4506 vec_pos[i] = !prev[i];
289 }
290 554066 y_flag = 1;
291 } else {
292 97039 vec_pos[i] = prev[i];
293 }
294 }
295 281245 }
296
297 8739072 static int get_value_cached(GetBitContext *gb, int vec_pos, uint8_t *vec,
298 int vec_size, int component, int shift, int *prev)
299 {
300
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 8739072 if (vec_pos < vec_size)
301 8442194 return vec[vec_pos];
302
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 296878 if (!get_bits1(gb))
303 46525 return prev[component];
304 250353 prev[component] = get_bits(gb, 8 - shift) << shift;
305 250353 return prev[component];
306 }
307
308 #define MKVAL(vals) ((vals)[0] | ((vals)[1] << 3) | ((vals)[2] << 6))
309
310 /* Image mode - the hardest to comprehend MSS4 coding mode.
311 *
312 * In this mode all three 16x16 blocks are coded together with a method
313 * remotely similar to the methods employed in MSS1-MSS3.
314 * The idea is that every component has a vector of 1-4 most common symbols
315 * and an escape mode for reading new value from the bitstream. Decoding
316 * consists of retrieving pixel values from the vector or reading new ones
317 * from the bitstream; depending on flags read from the bitstream, these vector
318 * positions can be updated or reused from the state of the previous line
319 * or previous pixel.
320 */
321 11379 static int mss4_decode_image_block(MSS4Context *ctx, GetBitContext *gb,
322 uint8_t *picdst[3], int mb_x, int mb_y)
323 {
324 uint8_t vec[3][4];
325 int vec_len[3];
326 int sel_len[3], sel_flag[3];
327 int i, j, k, mode, split;
328 11379 int prev_vec1 = 0, prev_split = 0;
329 11379 int vals[3] = { 0 };
330 11379 int prev_pix[3] = { 0 };
331 11379 int prev_mode[16] = { 0 };
332 uint8_t *dst[3];
333
334
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 11379 const int val_shift = ctx->quality == 100 ? 0 : 2;
335
336
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 45516 for (i = 0; i < 3; i++)
337 34137 dst[i] = ctx->imgbuf[i];
338
339
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 45516 for (i = 0; i < 3; i++) {
340 34137 vec_len[i] = vec_len_syms[!!i][get_unary(gb, 0, 3)];
341
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 129439 for (j = 0; j < vec_len[i]; j++) {
342 95302 vec[i][j] = get_coeff(gb, &vec_entry_vlc[!!i], 5, 1);
343 95302 vec[i][j] += ctx->prev_vec[i][j];
344 95302 ctx->prev_vec[i][j] = vec[i][j];
345 }
346 34137 sel_flag[i] = vec_len[i] > 1;
347 34137 sel_len[i] = vec_len[i] > 2 ? vec_len[i] - 2 : 0;
348 }
349
350
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 193443 for (j = 0; j < 16; j++) {
351
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 182064 if (get_bits1(gb)) {
352 56004 split = 0;
353
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 56004 if (get_bits1(gb)) {
354 35860 prev_mode[0] = 0;
355 35860 vals[0] = vals[1] = vals[2] = 0;
356 35860 mode = 2;
357 } else {
358 20144 mode = get_bits1(gb);
359
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 20144 if (mode)
360 3817 split = get_bits(gb, 4);
361 }
362
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 952068 for (i = 0; i < 16; i++) {
363
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 896064 if (mode <= 1) {
364 322304 vals[0] = prev_mode[i] & 7;
365 322304 vals[1] = (prev_mode[i] >> 3) & 7;
366 322304 vals[2] = prev_mode[i] >> 6;
367
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 322304 if (mode == 1 && i == split) {
368 3817 read_vec_pos(gb, vals, sel_flag, sel_len, vals);
369 }
370
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 573760 } else if (mode == 2) {
371
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 573760 if (get_bits1(gb))
372 261389 read_vec_pos(gb, vals, sel_flag, sel_len, vals);
373 }
374
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 3584256 for (k = 0; k < 3; k++)
375 2688192 *dst[k]++ = get_value_cached(gb, vals[k], vec[k],
376 vec_len[k], k,
377 val_shift, prev_pix);
378 896064 prev_mode[i] = MKVAL(vals);
379 }
380 } else {
381
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 126060 if (get_bits1(gb)) {
382 21425 split = get_bits(gb, 4);
383
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 21425 if (split >= prev_split)
384 15525 split++;
385 21425 prev_split = split;
386 } else {
387 104635 split = prev_split;
388 }
389
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 126060 if (split) {
390 109261 vals[0] = prev_mode[0] & 7;
391 109261 vals[1] = (prev_mode[0] >> 3) & 7;
392 109261 vals[2] = prev_mode[0] >> 6;
393
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 437044 for (i = 0; i < 3; i++) {
394
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 5442705 for (k = 0; k < split; k++) {
395 5114922 *dst[i]++ = get_value_cached(gb, vals[i], vec[i],
396 vec_len[i], i, val_shift,
397 prev_pix);
398 5114922 prev_mode[k] = MKVAL(vals);
399 }
400 }
401 }
402
403
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 126060 if (split != 16) {
404 22314 vals[0] = prev_vec1 & 7;
405 22314 vals[1] = (prev_vec1 >> 3) & 7;
406 22314 vals[2] = prev_vec1 >> 6;
407
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 22314 if (get_bits1(gb)) {
408 16039 read_vec_pos(gb, vals, sel_flag, sel_len, vals);
409 16039 prev_vec1 = MKVAL(vals);
410 }
411
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 89256 for (i = 0; i < 3; i++) {
412
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 1002900 for (k = 0; k < 16 - split; k++) {
413 935958 *dst[i]++ = get_value_cached(gb, vals[i], vec[i],
414 vec_len[i], i, val_shift,
415 prev_pix);
416 935958 prev_mode[split + k] = MKVAL(vals);
417 }
418 }
419 }
420 }
421 }
422
423
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424
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 580329 for (j = 0; j < 16; j++)
425 546192 memcpy(picdst[i] + mb_x * 16 + j * ctx->pic->linesize[i],
426 546192 ctx->imgbuf[i] + j * 16, 16);
427
428 11379 return 0;
429 }
430
431 175050 static inline void mss4_update_dc_cache(MSS4Context *c, int mb_x)
432 {
433 int i;
434
435 175050 c->dc_cache[0][TOP] = c->prev_dc[0][mb_x * 2 + 1];
436 175050 c->dc_cache[0][LEFT] = 0;
437 175050 c->dc_cache[1][TOP] = 0;
438 175050 c->dc_cache[1][LEFT] = 0;
439
440
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 525150 for (i = 0; i < 2; i++)
441 350100 c->prev_dc[0][mb_x * 2 + i] = 0;
442
443
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 525150 for (i = 1; i < 3; i++) {
444 350100 c->dc_cache[i + 1][TOP] = c->prev_dc[i][mb_x];
445 350100 c->dc_cache[i + 1][LEFT] = 0;
446 350100 c->prev_dc[i][mb_x] = 0;
447 }
448 175050 }
449
450 145 static int mss4_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
451 int *got_frame, AVPacket *avpkt)
452 {
453 145 const uint8_t *buf = avpkt->data;
454 145 int buf_size = avpkt->size;
455 145 MSS4Context *c = avctx->priv_data;
456 GetBitContext gb;
457 GetByteContext bc;
458 uint8_t *dst[3];
459 int width, height, quality, frame_type;
460 int x, y, i, mb_width, mb_height, blk_type;
461 int ret;
462
463
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 145 if (buf_size < HEADER_SIZE) {
464 ✗ av_log(avctx, AV_LOG_ERROR,
465 "Frame should have at least %d bytes, got %d instead\n",
466 HEADER_SIZE, buf_size);
467 ✗ return AVERROR_INVALIDDATA;
468 }
469
470 145 bytestream2_init(&bc, buf, buf_size);
471 145 width = bytestream2_get_be16(&bc);
472 145 height = bytestream2_get_be16(&bc);
473 145 bytestream2_skip(&bc, 2);
474 145 quality = bytestream2_get_byte(&bc);
475 145 frame_type = bytestream2_get_byte(&bc);
476
477
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 145 if (width > avctx->width ||
478
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 145 height != avctx->height) {
479 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d\n",
480 width, height);
481 ✗ return AVERROR_INVALIDDATA;
482 }
483
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 145 if (av_image_check_size2(width, height, avctx->max_pixels, AV_PIX_FMT_NONE, 0, avctx) < 0)
484 ✗ return AVERROR_INVALIDDATA;
485
486
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 145 if (quality < 1 || quality > 100) {
487 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid quality setting %d\n", quality);
488 ✗ return AVERROR_INVALIDDATA;
489 }
490
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 145 if ((frame_type & ~3) || frame_type == 3) {
491 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid frame type %d\n", frame_type);
492 ✗ return AVERROR_INVALIDDATA;
493 }
494
495
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 145 if (frame_type != SKIP_FRAME && !bytestream2_get_bytes_left(&bc)) {
496 ✗ av_log(avctx, AV_LOG_ERROR,
497 "Empty frame found but it is not a skip frame.\n");
498 ✗ return AVERROR_INVALIDDATA;
499 }
500 145 mb_width = FFALIGN(width, 16) >> 4;
501 145 mb_height = FFALIGN(height, 16) >> 4;
502
503
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 145 if (frame_type != SKIP_FRAME && 8*buf_size < 8*HEADER_SIZE + mb_width*mb_height)
504 ✗ return AVERROR_INVALIDDATA;
505
506
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 145 if ((ret = ff_reget_buffer(avctx, c->pic, 0)) < 0)
507 ✗ return ret;
508
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 145 if (frame_type == INTRA_FRAME)
509 3 c->pic->flags |= AV_FRAME_FLAG_KEY;
510 else
511 142 c->pic->flags &= ~AV_FRAME_FLAG_KEY;
512 145 c->pic->pict_type = (frame_type == INTRA_FRAME) ? AV_PICTURE_TYPE_I
513
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 145 : AV_PICTURE_TYPE_P;
514
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 145 if (frame_type == SKIP_FRAME) {
515 98 *got_frame = 1;
516
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 98 if ((ret = av_frame_ref(rframe, c->pic)) < 0)
517 ✗ return ret;
518
519 98 return buf_size;
520 }
521
522
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 47 if (c->quality != quality) {
523 2 c->quality = quality;
524
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 6 for (i = 0; i < 2; i++)
525 4 ff_mss34_gen_quant_mat(c->quant_mat[i], quality, !i);
526 }
527
528
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 47 if ((ret = init_get_bits8(&gb, buf + HEADER_SIZE, buf_size - HEADER_SIZE)) < 0)
529 ✗ return ret;
530 47 dst[0] = c->pic->data[0];
531 47 dst[1] = c->pic->data[1];
532 47 dst[2] = c->pic->data[2];
533
534 47 memset(c->prev_vec, 0, sizeof(c->prev_vec));
535
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 2519 for (y = 0; y < mb_height; y++) {
536 2472 memset(c->dc_cache, 0, sizeof(c->dc_cache));
537
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 191736 for (x = 0; x < mb_width; x++) {
538 189264 blk_type = decode012(&gb);
539
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 189264 switch (blk_type) {
540 14214 case DCT_BLOCK:
541
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 14214 if (mss4_decode_dct_block(c, &gb, dst, x, y) < 0) {
542 ✗ av_log(avctx, AV_LOG_ERROR,
543 "Error decoding DCT block %d,%d\n",
544 x, y);
545 ✗ return AVERROR_INVALIDDATA;
546 }
547 14214 break;
548 11379 case IMAGE_BLOCK:
549
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 11379 if (mss4_decode_image_block(c, &gb, dst, x, y) < 0) {
550 ✗ av_log(avctx, AV_LOG_ERROR,
551 "Error decoding VQ block %d,%d\n",
552 x, y);
553 ✗ return AVERROR_INVALIDDATA;
554 }
555 11379 break;
556 163671 case SKIP_BLOCK:
557
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 163671 if (frame_type == INTRA_FRAME) {
558 ✗ av_log(avctx, AV_LOG_ERROR, "Skip block in intra frame\n");
559 ✗ return AVERROR_INVALIDDATA;
560 }
561 163671 break;
562 }
563
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 189264 if (blk_type != DCT_BLOCK)
564 175050 mss4_update_dc_cache(c, x);
565 }
566 2472 dst[0] += c->pic->linesize[0] * 16;
567 2472 dst[1] += c->pic->linesize[1] * 16;
568 2472 dst[2] += c->pic->linesize[2] * 16;
569 }
570
571
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 47 if ((ret = av_frame_ref(rframe, c->pic)) < 0)
572 ✗ return ret;
573
574 47 *got_frame = 1;
575
576 47 return buf_size;
577 }
578
579 4 static av_cold int mss4_decode_end(AVCodecContext *avctx)
580 {
581 4 MSS4Context * const c = avctx->priv_data;
582 int i;
583
584 4 av_frame_free(&c->pic);
585
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 16 for (i = 0; i < 3; i++)
586 12 av_freep(&c->prev_dc[i]);
587
588 4 return 0;
589 }
590
591 4 static av_cold int mss4_decode_init(AVCodecContext *avctx)
592 {
593 static AVOnce init_static_once = AV_ONCE_INIT;
594 4 MSS4Context * const c = avctx->priv_data;
595 int i;
596
597
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 16 for (i = 0; i < 3; i++) {
598
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 12 c->dc_stride[i] = FFALIGN(avctx->width, 16) >> (2 + !!i);
599 12 c->prev_dc[i] = av_malloc_array(c->dc_stride[i], sizeof(**c->prev_dc));
600
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 12 if (!c->prev_dc[i]) {
601 ✗ av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");
602 ✗ return AVERROR(ENOMEM);
603 }
604 }
605
606 4 c->pic = av_frame_alloc();
607
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 4 if (!c->pic)
608 ✗ return AVERROR(ENOMEM);
609
610 4 avctx->pix_fmt = AV_PIX_FMT_YUV444P;
611
612 4 ff_thread_once(&init_static_once, mss4_init_vlcs);
613
614 4 return 0;
615 }
616
617 const FFCodec ff_mts2_decoder = {
618 .p.name = "mts2",
619 CODEC_LONG_NAME("MS Expression Encoder Screen"),
620 .p.type = AVMEDIA_TYPE_VIDEO,
621 .p.id = AV_CODEC_ID_MTS2,
622 .priv_data_size = sizeof(MSS4Context),
623 .init = mss4_decode_init,
624 .close = mss4_decode_end,
625 FF_CODEC_DECODE_CB(mss4_decode_frame),
626 .p.capabilities = AV_CODEC_CAP_DR1,
627 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
628 };
629