xref: /third_party/ffmpeg/libavcodec/h261enc.c (revision cabdff1a) 
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 "mpegvideodata.h"
38#include "mpegvideoenc.h"
39
40static uint8_t uni_h261_rl_len [64*64*2*2];
41#define UNI_ENC_INDEX(last,run,level) ((last)*128*64 + (run)*128 + (level))
42
43typedef struct H261EncContext {
44    MpegEncContext s;
45
46    H261Context common;
47
48    int gob_number;
49} H261EncContext;
50
51int ff_h261_get_picture_format(int width, int height)
52{
53    // QCIF
54    if (width == 176 && height == 144)
55        return 0;
56    // CIF
57    else if (width == 352 && height == 288)
58        return 1;
59    // ERROR
60    else
61        return AVERROR(EINVAL);
62}
63
64void ff_h261_encode_picture_header(MpegEncContext *s, int picture_number)
65{
66    H261EncContext *const h = (H261EncContext *)s;
67    int format, temp_ref;
68
69    align_put_bits(&s->pb);
70
71    /* Update the pointer to last GOB */
72    s->ptr_lastgob = put_bits_ptr(&s->pb);
73
74    put_bits(&s->pb, 20, 0x10); /* PSC */
75
76    temp_ref = s->picture_number * 30000LL * s->avctx->time_base.num /
77               (1001LL * s->avctx->time_base.den);   // FIXME maybe this should use a timestamp
78    put_sbits(&s->pb, 5, temp_ref); /* TemporalReference */
79
80    put_bits(&s->pb, 1, 0); /* split screen off */
81    put_bits(&s->pb, 1, 0); /* camera  off */
82    put_bits(&s->pb, 1, s->pict_type == AV_PICTURE_TYPE_I); /* freeze picture release on/off */
83
84    format = ff_h261_get_picture_format(s->width, s->height);
85
86    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
87
88    put_bits(&s->pb, 1, 1); /* still image mode */
89    put_bits(&s->pb, 1, 1); /* reserved */
90
91    put_bits(&s->pb, 1, 0); /* no PEI */
92    if (format == 0)
93        h->gob_number = -1;
94    else
95        h->gob_number = 0;
96    s->mb_skip_run = 0;
97}
98
99/**
100 * Encode a group of blocks header.
101 */
102static void h261_encode_gob_header(MpegEncContext *s, int mb_line)
103{
104    H261EncContext *const h = (H261EncContext *)s;
105    if (ff_h261_get_picture_format(s->width, s->height) == 0) {
106        h->gob_number += 2; // QCIF
107    } else {
108        h->gob_number++;    // CIF
109    }
110    put_bits(&s->pb, 16, 1);            /* GBSC */
111    put_bits(&s->pb, 4, h->gob_number); /* GN */
112    put_bits(&s->pb, 5, s->qscale);     /* GQUANT */
113    put_bits(&s->pb, 1, 0);             /* no GEI */
114    s->mb_skip_run = 0;
115    s->last_mv[0][0][0] = 0;
116    s->last_mv[0][0][1] = 0;
117}
118
119void ff_h261_reorder_mb_index(MpegEncContext *s)
120{
121    int index = s->mb_x + s->mb_y * s->mb_width;
122
123    if (index % 11 == 0) {
124        if (index % 33 == 0)
125            h261_encode_gob_header(s, 0);
126        s->last_mv[0][0][0] = 0;
127        s->last_mv[0][0][1] = 0;
128    }
129
130    /* for CIF the GOB's are fragmented in the middle of a scanline
131     * that's why we need to adjust the x and y index of the macroblocks */
132    if (ff_h261_get_picture_format(s->width, s->height) == 1) { // CIF
133        s->mb_x  = index % 11;
134        index   /= 11;
135        s->mb_y  = index % 3;
136        index   /= 3;
137        s->mb_x += 11 * (index % 2);
138        index   /= 2;
139        s->mb_y += 3 * index;
140
141        ff_init_block_index(s);
142        ff_update_block_index(s);
143    }
144}
145
146static void h261_encode_motion(PutBitContext *pb, int val)
147{
148    int sign, code;
149    if (val == 0) {
150        code = 0;
151        put_bits(pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
152    } else {
153        if (val > 15)
154            val -= 32;
155        if (val < -16)
156            val += 32;
157        sign = val < 0;
158        code = sign ? -val : val;
159        put_bits(pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
160        put_bits(pb, 1, sign);
161    }
162}
163
164static inline int get_cbp(MpegEncContext *s, int16_t block[6][64])
165{
166    int i, cbp;
167    cbp = 0;
168    for (i = 0; i < 6; i++)
169        if (s->block_last_index[i] >= 0)
170            cbp |= 1 << (5 - i);
171    return cbp;
172}
173
174/**
175 * Encode an 8x8 block.
176 * @param block the 8x8 block
177 * @param n block index (0-3 are luma, 4-5 are chroma)
178 */
179static void h261_encode_block(H261EncContext *h, int16_t *block, int n)
180{
181    MpegEncContext *const s = &h->s;
182    int level, run, i, j, last_index, last_non_zero, sign, slevel, code;
183    RLTable *rl;
184
185    rl = &ff_h261_rl_tcoeff;
186    if (s->mb_intra) {
187        /* DC coef */
188        level = block[0];
189        /* 255 cannot be represented, so we clamp */
190        if (level > 254) {
191            level    = 254;
192            block[0] = 254;
193        }
194        /* 0 cannot be represented also */
195        else if (level < 1) {
196            level    = 1;
197            block[0] = 1;
198        }
199        if (level == 128)
200            put_bits(&s->pb, 8, 0xff);
201        else
202            put_bits(&s->pb, 8, level);
203        i = 1;
204    } else if ((block[0] == 1 || block[0] == -1) &&
205               (s->block_last_index[n] > -1)) {
206        // special case
207        put_bits(&s->pb, 2, block[0] > 0 ? 2 : 3);
208        i = 1;
209    } else {
210        i = 0;
211    }
212
213    /* AC coefs */
214    last_index    = s->block_last_index[n];
215    last_non_zero = i - 1;
216    for (; i <= last_index; i++) {
217        j     = s->intra_scantable.permutated[i];
218        level = block[j];
219        if (level) {
220            run    = i - last_non_zero - 1;
221            sign   = 0;
222            slevel = level;
223            if (level < 0) {
224                sign  = 1;
225                level = -level;
226            }
227            code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/,
228                                run, level);
229            if (run == 0 && level < 16)
230                code += 1;
231            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
232            if (code == rl->n) {
233                put_bits(&s->pb, 6, run);
234                av_assert1(slevel != 0);
235                av_assert1(level <= 127);
236                put_sbits(&s->pb, 8, slevel);
237            } else {
238                put_bits(&s->pb, 1, sign);
239            }
240            last_non_zero = i;
241        }
242    }
243    if (last_index > -1)
244        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]); // EOB
245}
246
247void ff_h261_encode_mb(MpegEncContext *s, int16_t block[6][64],
248                       int motion_x, int motion_y)
249{
250    /* The following is only allowed because this encoder
251     * does not use slice threading. */
252    H261EncContext *const h = (H261EncContext *)s;
253    H261Context *const com = &h->common;
254    int mvd, mv_diff_x, mv_diff_y, i, cbp;
255    cbp = 63; // avoid warning
256    mvd = 0;
257
258    com->mtype = 0;
259
260    if (!s->mb_intra) {
261        /* compute cbp */
262        cbp = get_cbp(s, block);
263
264        /* mvd indicates if this block is motion compensated */
265        mvd = motion_x | motion_y;
266
267        if ((cbp | mvd) == 0) {
268            /* skip macroblock */
269            s->skip_count++;
270            s->mb_skip_run++;
271            s->last_mv[0][0][0] = 0;
272            s->last_mv[0][0][1] = 0;
273            s->qscale -= s->dquant;
274            return;
275        }
276    }
277
278    /* MB is not skipped, encode MBA */
279    put_bits(&s->pb,
280             ff_h261_mba_bits[s->mb_skip_run],
281             ff_h261_mba_code[s->mb_skip_run]);
282    s->mb_skip_run = 0;
283
284    /* calculate MTYPE */
285    if (!s->mb_intra) {
286        com->mtype++;
287
288        if (mvd || s->loop_filter)
289            com->mtype += 3;
290        if (s->loop_filter)
291            com->mtype += 3;
292        if (cbp)
293            com->mtype++;
294        av_assert1(com->mtype > 1);
295    }
296
297    if (s->dquant && cbp) {
298        com->mtype++;
299    } else
300        s->qscale -= s->dquant;
301
302    put_bits(&s->pb,
303             ff_h261_mtype_bits[com->mtype],
304             ff_h261_mtype_code[com->mtype]);
305
306    com->mtype = ff_h261_mtype_map[com->mtype];
307
308    if (IS_QUANT(com->mtype)) {
309        ff_set_qscale(s, s->qscale + s->dquant);
310        put_bits(&s->pb, 5, s->qscale);
311    }
312
313    if (IS_16X16(com->mtype)) {
314        mv_diff_x       = (motion_x >> 1) - s->last_mv[0][0][0];
315        mv_diff_y       = (motion_y >> 1) - s->last_mv[0][0][1];
316        s->last_mv[0][0][0] = (motion_x >> 1);
317        s->last_mv[0][0][1] = (motion_y >> 1);
318        h261_encode_motion(&s->pb, mv_diff_x);
319        h261_encode_motion(&s->pb, mv_diff_y);
320    }
321
322    if (HAS_CBP(com->mtype)) {
323        av_assert1(cbp > 0);
324        put_bits(&s->pb,
325                 ff_h261_cbp_tab[cbp - 1][1],
326                 ff_h261_cbp_tab[cbp - 1][0]);
327    }
328    for (i = 0; i < 6; i++)
329        /* encode each block */
330        h261_encode_block(h, block[i], i);
331
332    if (!IS_16X16(com->mtype)) {
333        s->last_mv[0][0][0] = 0;
334        s->last_mv[0][0][1] = 0;
335    }
336}
337
338static av_cold void init_uni_h261_rl_tab(const RLTable *rl, uint8_t *len_tab)
339{
340    int slevel, run, last;
341
342    av_assert0(MAX_LEVEL >= 64);
343    av_assert0(MAX_RUN   >= 63);
344
345    for(slevel=-64; slevel<64; slevel++){
346        if(slevel==0) continue;
347        for(run=0; run<64; run++){
348            for(last=0; last<=1; last++){
349                const int index= UNI_ENC_INDEX(last, run, slevel+64);
350                int level= slevel < 0 ? -slevel : slevel;
351                int len, code;
352
353                len_tab[index]= 100;
354
355                /* ESC0 */
356                code= get_rl_index(rl, 0, run, level);
357                len=  rl->table_vlc[code][1] + 1;
358                if(last)
359                    len += 2;
360
361                if(code!=rl->n && len < len_tab[index]){
362                    len_tab [index]= len;
363                }
364                /* ESC */
365                len = rl->table_vlc[rl->n][1];
366                if(last)
367                    len += 2;
368
369                if(len < len_tab[index]){
370                    len_tab [index]= len;
371                }
372            }
373        }
374    }
375}
376
377static av_cold void h261_encode_init_static(void)
378{
379    static uint8_t h261_rl_table_store[2][2 * MAX_RUN + MAX_LEVEL + 3];
380
381    ff_rl_init(&ff_h261_rl_tcoeff, h261_rl_table_store);
382    init_uni_h261_rl_tab(&ff_h261_rl_tcoeff, uni_h261_rl_len);
383}
384
385av_cold void ff_h261_encode_init(MpegEncContext *s)
386{
387    H261EncContext *const h = (H261EncContext*)s;
388    static AVOnce init_static_once = AV_ONCE_INIT;
389
390    s->private_ctx = &h->common;
391
392    s->min_qcoeff       = -127;
393    s->max_qcoeff       = 127;
394    s->y_dc_scale_table =
395    s->c_dc_scale_table = ff_mpeg1_dc_scale_table;
396    s->ac_esc_length    = 6+6+8;
397
398    s->intra_ac_vlc_length      = s->inter_ac_vlc_length      = uni_h261_rl_len;
399    s->intra_ac_vlc_last_length = s->inter_ac_vlc_last_length = uni_h261_rl_len + 128*64;
400    ff_thread_once(&init_static_once, h261_encode_init_static);
401}
402
403const FFCodec ff_h261_encoder = {
404    .p.name         = "h261",
405    .p.long_name    = NULL_IF_CONFIG_SMALL("H.261"),
406    .p.type         = AVMEDIA_TYPE_VIDEO,
407    .p.id           = AV_CODEC_ID_H261,
408    .p.priv_class   = &ff_mpv_enc_class,
409    .priv_data_size = sizeof(H261EncContext),
410    .init           = ff_mpv_encode_init,
411    FF_CODEC_ENCODE_CB(ff_mpv_encode_picture),
412    .close          = ff_mpv_encode_end,
413    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
414    .p.pix_fmts     = (const enum AVPixelFormat[]) { AV_PIX_FMT_YUV420P,
415                                                     AV_PIX_FMT_NONE },
416};
417