FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/tscc2.c
Date: 2025-07-01 21:35:40
Exec Total Coverage
Lines: 147 174 84.5%
Functions: 8 8 100.0%
Branches: 72 94 76.6%
Line Branch Exec Source
1 /*
2 * TechSmith Screen Codec 2 (aka Dora) 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 * TechSmith Screen Codec 2 decoder
25 */
26
27 #include <inttypes.h>
28
29 #include "libavutil/mem.h"
30 #include "libavutil/thread.h"
31
32 #define BITSTREAM_READER_LE
33 #include "avcodec.h"
34 #include "bytestream.h"
35 #include "codec_internal.h"
36 #include "decode.h"
37 #include "get_bits.h"
38 #include "mathops.h"
39 #include "tscc2data.h"
40
41 #define TSCC2_VLC_BITS 9
42
43 typedef struct TSCC2Context {
44 AVCodecContext *avctx;
45 AVFrame *pic;
46 int mb_width, mb_height;
47 uint8_t *slice_quants;
48 int quant[2];
49 int q[2][3];
50 GetBitContext gb;
51
52 int block[16];
53 } TSCC2Context;
54
55 static VLC dc_vlc, nc_vlc[NUM_VLC_SETS], ac_vlc[NUM_VLC_SETS];
56
57 54 static av_cold void tscc2_init_vlc(VLC *vlc, int *offset, int nb_codes,
58 const uint8_t *lens, const void *syms,
59 int sym_length)
60 {
61 static VLCElem vlc_buf[15442];
62
63 54 vlc->table = &vlc_buf[*offset];
64 54 vlc->table_allocated = FF_ARRAY_ELEMS(vlc_buf) - *offset;
65 54 ff_vlc_init_from_lengths(vlc, TSCC2_VLC_BITS, nb_codes,
66 lens, 1, syms, sym_length, sym_length, 0,
67 VLC_INIT_STATIC_OVERLONG | VLC_INIT_OUTPUT_LE, NULL);
68 54 *offset += vlc->table_size;
69 54 }
70
71 2 static av_cold void tscc2_init_vlcs(void)
72 {
73 2 const uint16_t *ac_vlc_syms = tscc2_ac_vlc_syms;
74 2 const uint8_t *ac_vlc_lens = tscc2_ac_vlc_lens;
75 2 int i, offset = 0;
76
77 2 tscc2_init_vlc(&dc_vlc, &offset, DC_VLC_COUNT,
78 tscc2_dc_vlc_lens, tscc2_dc_vlc_syms, 2);
79
80
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 28 for (i = 0; i < NUM_VLC_SETS; i++) {
81 26 tscc2_init_vlc(&nc_vlc[i], &offset, 16,
82 26 tscc2_nc_vlc_lens[i], tscc2_nc_vlc_syms[i], 1);
83
84 26 tscc2_init_vlc(&ac_vlc[i], &offset, tscc2_ac_vlc_sizes[i],
85 ac_vlc_lens, ac_vlc_syms, 2);
86 26 ac_vlc_lens += tscc2_ac_vlc_sizes[i];
87 26 ac_vlc_syms += tscc2_ac_vlc_sizes[i];
88 }
89 2 }
90
91 #define DEQUANT(val, q) (((q) * (val) + 0x80) >> 8)
92 #define DCT1D(d0, d1, d2, d3, s0, s1, s2, s3, OP) \
93 OP(d0, 5 * ((s0) + (s1) + (s2)) + 2 * (s3)); \
94 OP(d1, 5 * ((s0) - (s2) - (s3)) + 2 * (s1)); \
95 OP(d2, 5 * ((s0) - (s2) + (s3)) - 2 * (s1)); \
96 OP(d3, 5 * ((s0) - (s1) + (s2)) - 2 * (s3)); \
97
98 #define COL_OP(a, b) a = (b)
99 #define ROW_OP(a, b) a = ((b) + 0x20) >> 6
100
101 441488 static void tscc2_idct4_put(int *in, int q[3], uint8_t *dst, int stride)
102 {
103 int i;
104 int tblk[4 * 4];
105 int t0, t1, t2, t3;
106
107
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 2207440 for (i = 0; i < 4; i++) {
108 1765952 t0 = DEQUANT(q[0 + (i & 1)], in[0 * 4 + i]);
109 1765952 t1 = DEQUANT(q[1 + (i & 1)], in[1 * 4 + i]);
110 1765952 t2 = DEQUANT(q[0 + (i & 1)], in[2 * 4 + i]);
111 1765952 t3 = DEQUANT(q[1 + (i & 1)], in[3 * 4 + i]);
112 1765952 DCT1D(tblk[0 * 4 + i], tblk[1 * 4 + i],
113 tblk[2 * 4 + i], tblk[3 * 4 + i],
114 t0, t1, t2, t3, COL_OP);
115 }
116
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 2207440 for (i = 0; i < 4; i++) {
117 1765952 DCT1D(dst[0], dst[1], dst[2], dst[3],
118 tblk[i * 4 + 0], tblk[i * 4 + 1],
119 tblk[i * 4 + 2], tblk[i * 4 + 3], ROW_OP);
120 1765952 dst += stride;
121 }
122 441488 }
123
124 66141 static int tscc2_decode_mb(TSCC2Context *c, int *q, int vlc_set,
125 uint8_t *dst, int stride, int plane)
126 {
127 66141 GetBitContext *gb = &c->gb;
128 int prev_dc, dc, nc, ac, bpos, val;
129 int i, j, k, l;
130
131
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 66141 if (get_bits1(gb)) {
132
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 10955 if (get_bits1(gb)) {
133 10954 val = get_bits(gb, 8);
134
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 98586 for (i = 0; i < 8; i++, dst += stride)
135 87632 memset(dst, val, 16);
136 } else {
137
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 1 if (get_bits_left(gb) < 16 * 8 * 8)
138 ✗ return AVERROR_INVALIDDATA;
139
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 9 for (i = 0; i < 8; i++) {
140
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 136 for (j = 0; j < 16; j++)
141 128 dst[j] = get_bits(gb, 8);
142 8 dst += stride;
143 }
144 }
145 10955 return 0;
146 }
147
148 55186 prev_dc = 0;
149
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150
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 551860 for (k = 0; k < 4; k++) {
151
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 441488 if (!(j | k)) {
152 55186 dc = get_bits(gb, 8);
153 } else {
154 386302 dc = get_vlc2(gb, dc_vlc.table, TSCC2_VLC_BITS, 2);
155
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 386302 if (dc == 0x100)
156 22622 dc = get_bits(gb, 8);
157 }
158 441488 dc = (dc + prev_dc) & 0xFF;
159 441488 prev_dc = dc;
160 441488 c->block[0] = dc;
161
162 441488 nc = get_vlc2(gb, nc_vlc[vlc_set].table, TSCC2_VLC_BITS, 1);
163
164 441488 bpos = 1;
165 441488 memset(c->block + 1, 0, 15 * sizeof(*c->block));
166
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 2082935 for (l = 0; l < nc; l++) {
167 1641447 ac = get_vlc2(gb, ac_vlc[vlc_set].table, TSCC2_VLC_BITS, 2);
168
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 1641447 if (ac == 0x1000)
169 48321 ac = get_bits(gb, 12);
170 1641447 bpos += ac & 0xF;
171
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 1641447 if (bpos >= 16)
172 ✗ return AVERROR_INVALIDDATA;
173 1641447 val = sign_extend(ac >> 4, 8);
174 1641447 c->block[ff_zigzag_scan[bpos++]] = val;
175 }
176 441488 tscc2_idct4_put(c->block, q, dst + k * 4, stride);
177 }
178 110372 dst += 4 * stride;
179 }
180 55186 return 0;
181 }
182
183 1084 static int tscc2_decode_slice(TSCC2Context *c, int mb_y,
184 const uint8_t *buf, int buf_size)
185 {
186 int i, mb_x, q, ret;
187 int off;
188
189
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 1084 if ((ret = init_get_bits8(&c->gb, buf, buf_size)) < 0)
190 ✗ return ret;
191
192
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 34860 for (mb_x = 0; mb_x < c->mb_width; mb_x++) {
193 33776 q = c->slice_quants[mb_x + c->mb_width * mb_y];
194
195
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 33776 if (q == 0 || q == 3) // skip block
196 11729 continue;
197
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 88188 for (i = 0; i < 3; i++) {
198 66141 off = mb_x * 16 + mb_y * 8 * c->pic->linesize[i];
199 66141 ret = tscc2_decode_mb(c, c->q[q - 1], c->quant[q - 1] - 2,
200 66141 c->pic->data[i] + off, c->pic->linesize[i], i);
201
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 66141 if (ret)
202 ✗ return ret;
203 }
204 }
205
206 1084 return 0;
207 }
208
209 48 static int tscc2_decode_frame(AVCodecContext *avctx, AVFrame *rframe,
210 int *got_frame, AVPacket *avpkt)
211 {
212 48 const uint8_t *buf = avpkt->data;
213 48 int buf_size = avpkt->size;
214 48 TSCC2Context *c = avctx->priv_data;
215 GetByteContext gb;
216 uint32_t frame_type, size;
217 48 int i, val, len, pos = 0;
218 48 int num_mb = c->mb_width * c->mb_height;
219 int ret;
220
221 48 bytestream2_init(&gb, buf, buf_size);
222 48 frame_type = bytestream2_get_byte(&gb);
223
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 48 if (frame_type > 1) {
224 ✗ av_log(avctx, AV_LOG_ERROR, "Incorrect frame type %"PRIu32"\n",
225 frame_type);
226 ✗ return AVERROR_INVALIDDATA;
227 }
228
229
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 48 if (frame_type == 0) {
230 // Skip duplicate frames
231 17 return buf_size;
232 }
233
234
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 31 if ((ret = ff_reget_buffer(avctx, c->pic, 0)) < 0) {
235 ✗ return ret;
236 }
237
238
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 31 if (bytestream2_get_bytes_left(&gb) < 4) {
239 ✗ av_log(avctx, AV_LOG_ERROR, "Frame is too short\n");
240 ✗ return AVERROR_INVALIDDATA;
241 }
242
243 31 c->quant[0] = bytestream2_get_byte(&gb);
244 31 c->quant[1] = bytestream2_get_byte(&gb);
245
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 31 if (c->quant[0] < 2 || c->quant[0] > NUM_VLC_SETS + 1 ||
246
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 31 c->quant[1] < 2 || c->quant[1] > NUM_VLC_SETS + 1) {
247 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid quantisers %d / %d\n",
248 c->quant[0], c->quant[1]);
249 ✗ return AVERROR_INVALIDDATA;
250 }
251
252
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 124 for (i = 0; i < 3; i++) {
253 93 c->q[0][i] = tscc2_quants[c->quant[0] - 2][i];
254 93 c->q[1][i] = tscc2_quants[c->quant[1] - 2][i];
255 }
256
257 31 bytestream2_skip(&gb, 1);
258
259 31 size = bytestream2_get_le32(&gb);
260
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 31 if (size > bytestream2_get_bytes_left(&gb)) {
261 ✗ av_log(avctx, AV_LOG_ERROR, "Slice properties chunk is too large\n");
262 ✗ return AVERROR_INVALIDDATA;
263 }
264
265
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 3319 for (i = 0; i < size; i++) {
266 3288 val = bytestream2_get_byte(&gb);
267 3288 len = val & 0x3F;
268 3288 val >>= 6;
269
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 3288 if (pos + len > num_mb) {
270 ✗ av_log(avctx, AV_LOG_ERROR, "Too many slice properties\n");
271 ✗ return AVERROR_INVALIDDATA;
272 }
273 3288 memset(c->slice_quants + pos, val, len);
274 3288 pos += len;
275 }
276
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 31 if (pos < num_mb) {
277 ✗ av_log(avctx, AV_LOG_ERROR, "Too few slice properties (%d / %d)\n",
278 pos, num_mb);
279 ✗ return AVERROR_INVALIDDATA;
280 }
281
282
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 1115 for (i = 0; i < c->mb_height; i++) {
283 1085 size = bytestream2_peek_byte(&gb);
284
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 1085 if (size & 1) {
285 103 size = bytestream2_get_byte(&gb) - 1;
286 } else {
287 982 size = bytestream2_get_le32(&gb) >> 1;
288 }
289
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 1085 if (!size) {
290 103 int skip_row = 1, j, off = i * c->mb_width;
291
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 5871 for (j = 0; j < c->mb_width; j++) {
292
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 5768 if (c->slice_quants[off + j] == 1 ||
293
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 5768 c->slice_quants[off + j] == 2) {
294 ✗ skip_row = 0;
295 ✗ break;
296 }
297 }
298
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 103 if (!skip_row) {
299 ✗ av_log(avctx, AV_LOG_ERROR, "Non-skip row with zero size\n");
300 ✗ return AVERROR_INVALIDDATA;
301 }
302 }
303
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 1085 if (bytestream2_get_bytes_left(&gb) < size) {
304 1 av_log(avctx, AV_LOG_ERROR, "Invalid slice size (%"PRIu32"/%u)\n",
305 size, bytestream2_get_bytes_left(&gb));
306 1 return AVERROR_INVALIDDATA;
307 }
308 1084 ret = tscc2_decode_slice(c, i, buf + bytestream2_tell(&gb), size);
309
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 1084 if (ret) {
310 ✗ av_log(avctx, AV_LOG_ERROR, "Error decoding slice %d\n", i);
311 ✗ return ret;
312 }
313 1084 bytestream2_skip(&gb, size);
314 }
315
316 30 *got_frame = 1;
317
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 30 if ((ret = av_frame_ref(rframe, c->pic)) < 0)
318 ✗ return ret;
319
320 /* always report that the buffer was completely consumed */
321 30 return buf_size;
322 }
323
324 4 static av_cold int tscc2_decode_end(AVCodecContext *avctx)
325 {
326 4 TSCC2Context * const c = avctx->priv_data;
327
328 4 av_frame_free(&c->pic);
329 4 av_freep(&c->slice_quants);
330
331 4 return 0;
332 }
333
334 4 static av_cold int tscc2_decode_init(AVCodecContext *avctx)
335 {
336 4 TSCC2Context * const c = avctx->priv_data;
337 static AVOnce init_static_once = AV_ONCE_INIT;
338
339 4 c->avctx = avctx;
340
341 4 avctx->pix_fmt = AV_PIX_FMT_YUV444P;
342
343 4 c->mb_width = FFALIGN(avctx->width, 16) >> 4;
344 4 c->mb_height = FFALIGN(avctx->height, 8) >> 3;
345 4 c->slice_quants = av_malloc(c->mb_width * c->mb_height);
346
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 4 if (!c->slice_quants) {
347 ✗ av_log(avctx, AV_LOG_ERROR, "Cannot allocate slice information\n");
348 ✗ return AVERROR(ENOMEM);
349 }
350
351 4 c->pic = av_frame_alloc();
352
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 4 if (!c->pic)
353 ✗ return AVERROR(ENOMEM);
354
355 4 ff_thread_once(&init_static_once, tscc2_init_vlcs);
356
357 4 return 0;
358 }
359
360 const FFCodec ff_tscc2_decoder = {
361 .p.name = "tscc2",
362 CODEC_LONG_NAME("TechSmith Screen Codec 2"),
363 .p.type = AVMEDIA_TYPE_VIDEO,
364 .p.id = AV_CODEC_ID_TSCC2,
365 .priv_data_size = sizeof(TSCC2Context),
366 .init = tscc2_decode_init,
367 .close = tscc2_decode_end,
368 FF_CODEC_DECODE_CB(tscc2_decode_frame),
369 .p.capabilities = AV_CODEC_CAP_DR1,
370 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
371 };
372