FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/h261enc.c
Date: 2025-06-23 20:06:14
Exec Total Coverage
Lines: 184 195 94.4%
Functions: 9 9 100.0%
Branches: 67 80 83.8%
Line Branch Exec Source
1 /*
2 * H.261 encoder
3 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4 * Copyright (c) 2004 Maarten Daniels
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /**
24 * @file
25 * H.261 encoder.
26 */
27
28 #include "libavutil/attributes.h"
29 #include "libavutil/avassert.h"
30 #include "libavutil/thread.h"
31 #include "avcodec.h"
32 #include "codec_internal.h"
33 #include "mpegutils.h"
34 #include "mpegvideo.h"
35 #include "h261.h"
36 #include "h261enc.h"
37 #include "mpegvideoenc.h"
38 #include "put_bits.h"
39
40 #define H261_MAX_RUN 26
41 #define H261_MAX_LEVEL 15
42 #define H261_ESC_LEN (6 + 6 + 8)
43 #define MV_TAB_OFFSET 32
44
45 static struct VLCLUT {
46 uint8_t len;
47 uint16_t code;
48 } vlc_lut[H261_MAX_RUN + 1][32 /* 0..2 * H261_MAX_LEN are used */];
49
50 // Not const despite never being initialized because doing so would
51 // put it into .rodata instead of .bss and bloat the binary.
52 // mv_penalty exists so that the motion estimation code can avoid branches.
53 static uint8_t mv_penalty[MAX_FCODE + 1][MAX_DMV * 2 + 1];
54 static uint8_t uni_h261_rl_len [64 * 128];
55 static uint8_t uni_h261_rl_len_last[64 * 128];
56 static uint8_t h261_mv_codes[64][2];
57
58 typedef struct H261EncContext {
59 MPVMainEncContext s;
60
61 H261Context common;
62
63 int gob_number;
64 enum {
65 H261_QCIF = 0,
66 H261_CIF = 1,
67 } format;
68 } H261EncContext;
69
70 300 static int h261_encode_picture_header(MPVMainEncContext *const m)
71 {
72 300 H261EncContext *const h = (H261EncContext *)m;
73 300 MPVEncContext *const s = &h->s.s;
74 int temp_ref;
75
76 300 put_bits_assume_flushed(&s->pb);
77
78 300 put_bits(&s->pb, 20, 0x10); /* PSC */
79
80 300 temp_ref = s->c.picture_number * 30000LL * s->c.avctx->time_base.num /
81 300 (1001LL * s->c.avctx->time_base.den); // FIXME maybe this should use a timestamp
82 300 put_sbits(&s->pb, 5, temp_ref); /* TemporalReference */
83
84 300 put_bits(&s->pb, 1, 0); /* split screen off */
85 300 put_bits(&s->pb, 1, 0); /* camera off */
86 300 put_bits(&s->pb, 1, s->c.pict_type == AV_PICTURE_TYPE_I); /* freeze picture release on/off */
87
88 300 put_bits(&s->pb, 1, h->format); /* 0 == QCIF, 1 == CIF */
89
90 300 put_bits(&s->pb, 1, 1); /* still image mode */
91 300 put_bits(&s->pb, 1, 1); /* reserved */
92
93 300 put_bits(&s->pb, 1, 0); /* no PEI */
94 300 h->gob_number = h->format - 1;
95 300 s->c.mb_skip_run = 0;
96
97 300 return 0;
98 }
99
100 /**
101 * Encode a group of blocks header.
102 */
103 3600 static void h261_encode_gob_header(MPVEncContext *const s, int mb_line)
104 {
105 3600 H261EncContext *const h = (H261EncContext *)s;
106
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 3600 if (h->format == H261_QCIF) {
107 ✗ h->gob_number += 2; // QCIF
108 } else {
109 3600 h->gob_number++; // CIF
110 }
111 3600 put_bits(&s->pb, 16, 1); /* GBSC */
112 3600 put_bits(&s->pb, 4, h->gob_number); /* GN */
113 3600 put_bits(&s->pb, 5, s->c.qscale); /* GQUANT */
114 3600 put_bits(&s->pb, 1, 0); /* no GEI */
115 3600 s->c.mb_skip_run = 0;
116 3600 s->c.last_mv[0][0][0] = 0;
117 3600 s->c.last_mv[0][0][1] = 0;
118 3600 }
119
120 118800 void ff_h261_reorder_mb_index(MPVEncContext *const s)
121 {
122 118800 const H261EncContext *const h = (H261EncContext*)s;
123 118800 int index = s->c.mb_x + s->c.mb_y * s->c.mb_width;
124
125
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 118800 if (index % 11 == 0) {
126
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 10800 if (index % 33 == 0)
127 3600 h261_encode_gob_header(s, 0);
128 10800 s->c.last_mv[0][0][0] = 0;
129 10800 s->c.last_mv[0][0][1] = 0;
130 }
131
132 /* for CIF the GOB's are fragmented in the middle of a scanline
133 * that's why we need to adjust the x and y index of the macroblocks */
134
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 118800 if (h->format == H261_CIF) {
135 118800 s->c.mb_x = index % 11;
136 118800 index /= 11;
137 118800 s->c.mb_y = index % 3;
138 118800 index /= 3;
139 118800 s->c.mb_x += 11 * (index % 2);
140 118800 index /= 2;
141 118800 s->c.mb_y += 3 * index;
142
143 118800 ff_init_block_index(&s->c);
144 118800 ff_update_block_index(&s->c, 8, 0, 1);
145 }
146 118800 }
147
148 205596 static void h261_encode_motion(PutBitContext *pb, int val)
149 {
150 205596 put_bits(pb, h261_mv_codes[MV_TAB_OFFSET + val][1],
151 205596 h261_mv_codes[MV_TAB_OFFSET + val][0]);
152 205596 }
153
154 105360 static inline int get_cbp(const int block_last_index[6])
155 {
156 int i, cbp;
157 105360 cbp = 0;
158
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 737520 for (i = 0; i < 6; i++)
159
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 632160 if (block_last_index[i] >= 0)
160 276433 cbp |= 1 << (5 - i);
161 105360 return cbp;
162 }
163
164 /**
165 * Encode an 8x8 block.
166 * @param block the 8x8 block
167 * @param n block index (0-3 are luma, 4-5 are chroma)
168 */
169 796986 static void h261_encode_block(H261EncContext *h, int16_t *block, int n)
170 {
171 796986 MPVEncContext *const s = &h->s.s;
172 int level, run, i, j, last_index, last_non_zero;
173
174
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 796986 if (s->c.mb_intra) {
175 /* DC coef */
176 169980 level = block[0];
177 /* 255 cannot be represented, so we clamp */
178
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 169980 if (level > 254) {
179 ✗ level = 254;
180 ✗ block[0] = 254;
181 }
182 /* 0 cannot be represented also */
183
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 169980 else if (level < 1) {
184 ✗ level = 1;
185 ✗ block[0] = 1;
186 }
187
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 169980 if (level == 128)
188 2035 put_bits(&s->pb, 8, 0xff);
189 else
190 167945 put_bits(&s->pb, 8, level);
191 169980 i = 1;
192
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 627006 } else if ((block[0] == 1 || block[0] == -1) &&
193
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 131183 (s->c.block_last_index[n] > -1)) {
194 // special case
195
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 92217 put_bits(&s->pb, 2, block[0] > 0 ? 2 : 3);
196 92217 i = 1;
197 } else {
198 534789 i = 0;
199 }
200
201 /* AC coefs */
202 796986 last_index = s->c.block_last_index[n];
203 796986 last_non_zero = i - 1;
204
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 9791937 for (; i <= last_index; i++) {
205 8994951 j = s->c.intra_scantable.permutated[i];
206 8994951 level = block[j];
207
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 8994951 if (level) {
208 2936627 run = i - last_non_zero - 1;
209
210
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 2936627 if (run <= H261_MAX_RUN &&
211
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 2928932 (unsigned)(level + H261_MAX_LEVEL) <= 2 * H261_MAX_LEVEL &&
212
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 2925517 vlc_lut[run][level + H261_MAX_LEVEL].len) {
213 2894680 put_bits(&s->pb, vlc_lut[run][level + H261_MAX_LEVEL].len,
214 2894680 vlc_lut[run][level + H261_MAX_LEVEL].code);
215 } else {
216 /* Escape */
217 41947 put_bits(&s->pb, 6 + 6, (1 << 6) | run);
218 av_assert1(level != 0);
219 av_assert1(FFABS(level) <= 127);
220 41947 put_sbits(&s->pb, 8, level);
221 }
222 2936627 last_non_zero = i;
223 }
224 }
225
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 796986 if (last_index > -1)
226 446413 put_bits(&s->pb, 2, 0x2); // EOB
227 796986 }
228
229 133690 static void h261_encode_mb(MPVEncContext *const s, int16_t block[6][64],
230 int motion_x, int motion_y)
231 {
232 /* The following is only allowed because this encoder
233 * does not use slice threading. */
234 133690 H261EncContext *const h = (H261EncContext *)s;
235 133690 H261Context *const com = &h->common;
236 int mvd, mv_diff_x, mv_diff_y, i, cbp;
237 133690 cbp = 63; // avoid warning
238 133690 mvd = 0;
239
240 133690 com->mtype = 0;
241
242
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 133690 if (!s->c.mb_intra) {
243 /* compute cbp */
244 105360 cbp = get_cbp(s->c.block_last_index);
245
246 /* mvd indicates if this block is motion compensated */
247 105360 mvd = motion_x | motion_y;
248
249
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 105360 if ((cbp | mvd) == 0) {
250 /* skip macroblock */
251 859 s->c.mb_skip_run++;
252 859 s->c.last_mv[0][0][0] = 0;
253 859 s->c.last_mv[0][0][1] = 0;
254 859 s->c.qscale -= s->dquant;
255 859 return;
256 }
257 }
258
259 /* MB is not skipped, encode MBA */
260 132831 put_bits(&s->pb,
261 132831 ff_h261_mba_bits[s->c.mb_skip_run],
262 132831 ff_h261_mba_code[s->c.mb_skip_run]);
263 132831 s->c.mb_skip_run = 0;
264
265 /* calculate MTYPE */
266
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 132831 if (!s->c.mb_intra) {
267 104501 com->mtype++;
268
269
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 104501 if (mvd || s->c.loop_filter)
270 102798 com->mtype += 3;
271
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 104501 if (s->c.loop_filter)
272 51663 com->mtype += 3;
273
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 104501 if (cbp)
274 85004 com->mtype++;
275 av_assert1(com->mtype > 1);
276 }
277
278
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 132831 if (s->dquant && cbp) {
279 ✗ com->mtype++;
280 } else
281 132831 s->c.qscale -= s->dquant;
282
283 132831 put_bits(&s->pb,
284 132831 ff_h261_mtype_bits[com->mtype],
285 132831 ff_h261_mtype_code[com->mtype]);
286
287 132831 com->mtype = ff_h261_mtype_map[com->mtype];
288
289
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 132831 if (IS_QUANT(com->mtype)) {
290 ✗ ff_set_qscale(&s->c, s->c.qscale + s->dquant);
291 ✗ put_bits(&s->pb, 5, s->c.qscale);
292 }
293
294
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 132831 if (IS_16X16(com->mtype)) {
295 102798 mv_diff_x = (motion_x >> 1) - s->c.last_mv[0][0][0];
296 102798 mv_diff_y = (motion_y >> 1) - s->c.last_mv[0][0][1];
297 102798 s->c.last_mv[0][0][0] = (motion_x >> 1);
298 102798 s->c.last_mv[0][0][1] = (motion_y >> 1);
299 102798 h261_encode_motion(&s->pb, mv_diff_x);
300 102798 h261_encode_motion(&s->pb, mv_diff_y);
301 }
302
303
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 132831 if (HAS_CBP(com->mtype)) {
304 av_assert1(cbp > 0);
305 85004 put_bits(&s->pb,
306 85004 ff_h261_cbp_tab[cbp - 1][1],
307 85004 ff_h261_cbp_tab[cbp - 1][0]);
308 }
309
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 929817 for (i = 0; i < 6; i++)
310 /* encode each block */
311 796986 h261_encode_block(h, block[i], i);
312
313
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 132831 if (!IS_16X16(com->mtype)) {
314 30033 s->c.last_mv[0][0][0] = 0;
315 30033 s->c.last_mv[0][0][1] = 0;
316 }
317 }
318
319 6 static av_cold void h261_encode_init_static(void)
320 {
321 6 uint8_t (*const mv_codes)[2] = h261_mv_codes + MV_TAB_OFFSET;
322 6 memset(uni_h261_rl_len, H261_ESC_LEN, sizeof(uni_h261_rl_len));
323 6 memset(uni_h261_rl_len_last, H261_ESC_LEN + 2 /* EOB */, sizeof(uni_h261_rl_len_last));
324
325 // The following loop is over the ordinary elements, not EOB or escape.
326
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 384 for (size_t i = 1; i < FF_ARRAY_ELEMS(ff_h261_tcoeff_vlc) - 1; i++) {
327 378 unsigned run = ff_h261_tcoeff_run[i];
328 378 unsigned level = ff_h261_tcoeff_level[i];
329 378 unsigned len = ff_h261_tcoeff_vlc[i][1] + 1 /* sign */;
330 378 unsigned code = ff_h261_tcoeff_vlc[i][0];
331
332 378 vlc_lut[run][H261_MAX_LEVEL + level] = (struct VLCLUT){ len, code << 1 };
333 378 vlc_lut[run][H261_MAX_LEVEL - level] = (struct VLCLUT){ len, (code << 1) | 1 };
334
335 378 uni_h261_rl_len [UNI_AC_ENC_INDEX(run, 64 + level)] = len;
336 378 uni_h261_rl_len [UNI_AC_ENC_INDEX(run, 64 - level)] = len;
337 378 uni_h261_rl_len_last[UNI_AC_ENC_INDEX(run, 64 + level)] = len + 2;
338 378 uni_h261_rl_len_last[UNI_AC_ENC_INDEX(run, 64 - level)] = len + 2;
339 }
340
341 6 for (ptrdiff_t i = 1;; i++) {
342 // sign-one MV codes; diff -16..-1, 16..31
343 96 mv_codes[32 - i][0] = mv_codes[-i][0] = (ff_h261_mv_tab[i][0] << 1) | 1 /* sign */;
344 96 mv_codes[32 - i][1] = mv_codes[-i][1] = ff_h261_mv_tab[i][1] + 1;
345
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 96 if (i == 16)
346 6 break;
347 // sign-zero MV codes: diff -31..-17, 1..15
348 90 mv_codes[i][0] = mv_codes[i - 32][0] = ff_h261_mv_tab[i][0] << 1;
349 90 mv_codes[i][1] = mv_codes[i - 32][1] = ff_h261_mv_tab[i][1] + 1;
350 }
351 // MV code for difference zero; has no sign
352 6 mv_codes[0][0] = 1;
353 6 mv_codes[0][1] = 1;
354 6 }
355
356 6 static av_cold int h261_encode_init(AVCodecContext *avctx)
357 {
358 static AVOnce init_static_once = AV_ONCE_INIT;
359 6 H261EncContext *const h = avctx->priv_data;
360 6 MPVEncContext *const s = &h->s.s;
361
362
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 6 if (avctx->width == 176 && avctx->height == 144) {
363 ✗ h->format = H261_QCIF;
364
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 6 } else if (avctx->width == 352 && avctx->height == 288) {
365 6 h->format = H261_CIF;
366 } else {
367 ✗ av_log(avctx, AV_LOG_ERROR,
368 "The specified picture size of %dx%d is not valid for the "
369 "H.261 codec.\nValid sizes are 176x144, 352x288\n",
370 avctx->width, avctx->height);
371 ✗ return AVERROR(EINVAL);
372 }
373 6 s->c.private_ctx = &h->common;
374 6 h->s.encode_picture_header = h261_encode_picture_header;
375 6 s->encode_mb = h261_encode_mb;
376
377 6 s->min_qcoeff = -127;
378 6 s->max_qcoeff = 127;
379 6 s->ac_esc_length = H261_ESC_LEN;
380
381 6 s->me.mv_penalty = mv_penalty;
382
383 6 s->intra_ac_vlc_length = s->inter_ac_vlc_length = uni_h261_rl_len;
384 6 s->intra_ac_vlc_last_length = s->inter_ac_vlc_last_length = uni_h261_rl_len_last;
385 6 ff_thread_once(&init_static_once, h261_encode_init_static);
386
387 6 return ff_mpv_encode_init(avctx);
388 }
389
390 const FFCodec ff_h261_encoder = {
391 .p.name = "h261",
392 CODEC_LONG_NAME("H.261"),
393 .p.type = AVMEDIA_TYPE_VIDEO,
394 .p.id = AV_CODEC_ID_H261,
395 .p.priv_class = &ff_mpv_enc_class,
396 .p.capabilities = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_ENCODER_REORDERED_OPAQUE,
397 .priv_data_size = sizeof(H261EncContext),
398 .init = h261_encode_init,
399 FF_CODEC_ENCODE_CB(ff_mpv_encode_picture),
400 .close = ff_mpv_encode_end,
401 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
402 CODEC_PIXFMTS(AV_PIX_FMT_YUV420P),
403 .color_ranges = AVCOL_RANGE_MPEG,
404 };
405