libavcodec/h261enc.c

   1 /*
   2  * H261 encoder
   3  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   4  * Copyright (c) 2004 Maarten Daniels
   5  *
   6  * This file is part of Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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 "avcodec.h"
  30 #include "mpegutils.h"
  31 #include "mpegvideo.h"
  32 #include "h263.h"
  33 #include "h261.h"
  34 #include "mpegvideodata.h"
  35
  36 int ff_h261_get_picture_format(int width, int height)
  37 {
  38     // QCIF
  39     if (width == 176 && height == 144)
  40         return 0;
  41     // CIF
  42     else if (width == 352 && height == 288)
  43         return 1;
  44     // ERROR
  45     else
  46         return -1;
  47 }
  48
  49 void ff_h261_encode_picture_header(MpegEncContext *s, int picture_number)
  50 {
  51     H261Context *h = (H261Context *)s;
  52     int format, temp_ref;
  53
  54     avpriv_align_put_bits(&s->pb);
  55
  56     /* Update the pointer to last GOB */
  57     s->ptr_lastgob = put_bits_ptr(&s->pb);
  58
  59     put_bits(&s->pb, 20, 0x10); /* PSC */
  60
  61     temp_ref = s->picture_number * (int64_t)30000 * s->avctx->time_base.num /
  62                (1001 * (int64_t)s->avctx->time_base.den);   // FIXME maybe this should use a timestamp
  63     put_sbits(&s->pb, 5, temp_ref); /* TemporalReference */
  64
  65     put_bits(&s->pb, 1, 0); /* split screen off */
  66     put_bits(&s->pb, 1, 0); /* camera  off */
  67     put_bits(&s->pb, 1, 0); /* freeze picture release off */
  68
  69     format = ff_h261_get_picture_format(s->width, s->height);
  70
  71     put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
  72
  73     put_bits(&s->pb, 1, 1); /* still image mode */
  74     put_bits(&s->pb, 1, 1); /* reserved */
  75
  76     put_bits(&s->pb, 1, 0); /* no PEI */
  77     if (format == 0)
  78         h->gob_number = -1;
  79     else
  80         h->gob_number = 0;
  81     h->current_mba = 0;
  82 }
  83
  84 /**
  85  * Encode a group of blocks header.
  86  */
  87 static void h261_encode_gob_header(MpegEncContext *s, int mb_line)
  88 {
  89     H261Context *h = (H261Context *)s;
  90     if (ff_h261_get_picture_format(s->width, s->height) == 0) {
  91         h->gob_number += 2; // QCIF
  92     } else {
  93         h->gob_number++;    // CIF
  94     }
  95     put_bits(&s->pb, 16, 1);            /* GBSC */
  96     put_bits(&s->pb, 4, h->gob_number); /* GN */
  97     put_bits(&s->pb, 5, s->qscale);     /* GQUANT */
  98     put_bits(&s->pb, 1, 0);             /* no GEI */
  99     h->current_mba  = 0;
 100     h->previous_mba = 0;
 101     h->current_mv_x = 0;
 102     h->current_mv_y = 0;
 103 }
 104
 105 void ff_h261_reorder_mb_index(MpegEncContext *s)
 106 {
 107     int index = s->mb_x + s->mb_y * s->mb_width;
 108
 109     if (index % 33 == 0)
 110         h261_encode_gob_header(s, 0);
 111
 112     /* for CIF the GOB's are fragmented in the middle of a scanline
 113      * that's why we need to adjust the x and y index of the macroblocks */
 114     if (ff_h261_get_picture_format(s->width, s->height) == 1) { // CIF
 115         s->mb_x  = index % 11;
 116         index   /= 11;
 117         s->mb_y  = index % 3;
 118         index   /= 3;
 119         s->mb_x += 11 * (index % 2);
 120         index   /= 2;
 121         s->mb_y += 3 * index;
 122
 123         ff_init_block_index(s);
 124         ff_update_block_index(s);
 125     }
 126 }
 127
 128 static void h261_encode_motion(H261Context *h, int val)
 129 {
 130     MpegEncContext *const s = &h->s;
 131     int sign, code;
 132     if (val == 0) {
 133         code = 0;
 134         put_bits(&s->pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
 135     } else {
 136         if (val > 15)
 137             val -= 32;
 138         if (val < -16)
 139             val += 32;
 140         sign = val < 0;
 141         code = sign ? -val : val;
 142         put_bits(&s->pb, ff_h261_mv_tab[code][1], ff_h261_mv_tab[code][0]);
 143         put_bits(&s->pb, 1, sign);
 144     }
 145 }
 146
 147 static inline int get_cbp(MpegEncContext *s, int16_t block[6][64])
 148 {
 149     int i, cbp;
 150     cbp = 0;
 151     for (i = 0; i < 6; i++)
 152         if (s->block_last_index[i] >= 0)
 153             cbp |= 1 << (5 - i);
 154     return cbp;
 155 }
 156
 157 /**
 158  * Encode an 8x8 block.
 159  * @param block the 8x8 block
 160  * @param n block index (0-3 are luma, 4-5 are chroma)
 161  */
 162 static void h261_encode_block(H261Context *h, int16_t *block, int n)
 163 {
 164     MpegEncContext *const s = &h->s;
 165     int level, run, i, j, last_index, last_non_zero, sign, slevel, code;
 166     RLTable *rl;
 167
 168     rl = &ff_h261_rl_tcoeff;
 169     if (s->mb_intra) {
 170         /* DC coef */
 171         level = block[0];
 172         /* 255 cannot be represented, so we clamp */
 173         if (level > 254) {
 174             level    = 254;
 175             block[0] = 254;
 176         }
 177         /* 0 cannot be represented also */
 178         else if (level < 1) {
 179             level    = 1;
 180             block[0] = 1;
 181         }
 182         if (level == 128)
 183             put_bits(&s->pb, 8, 0xff);
 184         else
 185             put_bits(&s->pb, 8, level);
 186         i = 1;
 187     } else if ((block[0] == 1 || block[0] == -1) &&
 188                (s->block_last_index[n] > -1)) {
 189         // special case
 190         put_bits(&s->pb, 2, block[0] > 0 ? 2 : 3);
 191         i = 1;
 192     } else {
 193         i = 0;
 194     }
 195
 196     /* AC coefs */
 197     last_index    = s->block_last_index[n];
 198     last_non_zero = i - 1;
 199     for (; i <= last_index; i++) {
 200         j     = s->intra_scantable.permutated[i];
 201         level = block[j];
 202         if (level) {
 203             run    = i - last_non_zero - 1;
 204             sign   = 0;
 205             slevel = level;
 206             if (level < 0) {
 207                 sign  = 1;
 208                 level = -level;
 209             }
 210             code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/,
 211                                 run, level);
 212             if (run == 0 && level < 16)
 213                 code += 1;
 214             put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
 215             if (code == rl->n) {
 216                 put_bits(&s->pb, 6, run);
 217                 assert(slevel != 0);
 218                 assert(level <= 127);
 219                 put_sbits(&s->pb, 8, slevel);
 220             } else {
 221                 put_bits(&s->pb, 1, sign);
 222             }
 223             last_non_zero = i;
 224         }
 225     }
 226     if (last_index > -1)
 227         put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]); // EOB
 228 }
 229
 230 void ff_h261_encode_mb(MpegEncContext *s, int16_t block[6][64],
 231                        int motion_x, int motion_y)
 232 {
 233     H261Context *h = (H261Context *)s;
 234     int mvd, mv_diff_x, mv_diff_y, i, cbp;
 235     cbp = 63; // avoid warning
 236     mvd = 0;
 237
 238     h->current_mba++;
 239     h->mtype = 0;
 240
 241     if (!s->mb_intra) {
 242         /* compute cbp */
 243         cbp = get_cbp(s, block);
 244
 245         /* mvd indicates if this block is motion compensated */
 246         mvd = motion_x | motion_y;
 247
 248         if ((cbp | mvd | s->dquant) == 0) {
 249             /* skip macroblock */
 250             s->skip_count++;
 251             h->current_mv_x = 0;
 252             h->current_mv_y = 0;
 253             return;
 254         }
 255     }
 256
 257     /* MB is not skipped, encode MBA */
 258     put_bits(&s->pb,
 259              ff_h261_mba_bits[(h->current_mba - h->previous_mba) - 1],
 260              ff_h261_mba_code[(h->current_mba - h->previous_mba) - 1]);
 261
 262     /* calculate MTYPE */
 263     if (!s->mb_intra) {
 264         h->mtype++;
 265
 266         if (mvd || s->loop_filter)
 267             h->mtype += 3;
 268         if (s->loop_filter)
 269             h->mtype += 3;
 270         if (cbp || s->dquant)
 271             h->mtype++;
 272         assert(h->mtype > 1);
 273     }
 274
 275     if (s->dquant)
 276         h->mtype++;
 277
 278     put_bits(&s->pb,
 279              ff_h261_mtype_bits[h->mtype],
 280              ff_h261_mtype_code[h->mtype]);
 281
 282     h->mtype = ff_h261_mtype_map[h->mtype];
 283
 284     if (IS_QUANT(h->mtype)) {
 285         ff_set_qscale(s, s->qscale + s->dquant);
 286         put_bits(&s->pb, 5, s->qscale);
 287     }
 288
 289     if (IS_16X16(h->mtype)) {
 290         mv_diff_x       = (motion_x >> 1) - h->current_mv_x;
 291         mv_diff_y       = (motion_y >> 1) - h->current_mv_y;
 292         h->current_mv_x = (motion_x >> 1);
 293         h->current_mv_y = (motion_y >> 1);
 294         h261_encode_motion(h, mv_diff_x);
 295         h261_encode_motion(h, mv_diff_y);
 296     }
 297
 298     h->previous_mba = h->current_mba;
 299
 300     if (HAS_CBP(h->mtype)) {
 301         assert(cbp > 0);
 302         put_bits(&s->pb,
 303                  ff_h261_cbp_tab[cbp - 1][1],
 304                  ff_h261_cbp_tab[cbp - 1][0]);
 305     }
 306     for (i = 0; i < 6; i++)
 307         /* encode each block */
 308         h261_encode_block(h, block[i], i);
 309
 310     if ((h->current_mba == 11) || (h->current_mba == 22) ||
 311         (h->current_mba == 33) || (!IS_16X16(h->mtype))) {
 312         h->current_mv_x = 0;
 313         h->current_mv_y = 0;
 314     }
 315 }
 316
 317 av_cold void ff_h261_encode_init(MpegEncContext *s)
 318 {
 319     ff_h261_common_init();
 320
 321     s->min_qcoeff       = -127;
 322     s->max_qcoeff       = 127;
 323     s->y_dc_scale_table =
 324     s->c_dc_scale_table = ff_mpeg1_dc_scale_table;
 325 }
 326
 327 static const AVClass h261_class = {
 328     .class_name = "h261 encoder",
 329     .item_name  = av_default_item_name,
 330     .option     = ff_mpv_generic_options,
 331     .version    = LIBAVUTIL_VERSION_INT,
 332 };
 333
 334 AVCodec ff_h261_encoder = {
 335     .name           = "h261",
 336     .long_name      = NULL_IF_CONFIG_SMALL("H.261"),
 337     .type           = AVMEDIA_TYPE_VIDEO,
 338     .id             = AV_CODEC_ID_H261,
 339     .priv_data_size = sizeof(H261Context),
 340     .init           = ff_mpv_encode_init,
 341     .encode2        = ff_mpv_encode_picture,
 342     .close          = ff_mpv_encode_end,
 343     .pix_fmts       = (const enum AVPixelFormat[]) { AV_PIX_FMT_YUV420P,
 344                                                      AV_PIX_FMT_NONE },
 345     .priv_class     = &h261_class,
 346 };