libavcodec/vp6.c

   1 /**
   2  * @file vp6.c
   3  * VP6 compatible video decoder
   4  *
   5  * Copyright (C) 2006  Aurelien Jacobs <aurel@gnuage.org>
   6  *
   7  * The VP6F decoder accepts an optional 1 byte extradata. It is composed of:
   8  *  - upper 4bits: difference between encoded width and visible width
   9  *  - lower 4bits: difference between encoded height and visible height
  10  *
  11  * This file is part of FFmpeg.
  12  *
  13  * FFmpeg is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU Lesser General Public
  15  * License as published by the Free Software Foundation; either
  16  * version 2.1 of the License, or (at your option) any later version.
  17  *
  18  * FFmpeg is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21  * Lesser General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU Lesser General Public
  24  * License along with FFmpeg; if not, write to the Free Software
  25  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  26  */
  27
  28 #include <stdlib.h>
  29
  30 #include "avcodec.h"
  31 #include "dsputil.h"
  32 #include "bitstream.h"
  33 #include "huffman.h"
  34
  35 #include "vp56.h"
  36 #include "vp56data.h"
  37 #include "vp6data.h"
  38
  39
  40 static void vp6_parse_coeff(vp56_context_t *s);
  41 static void vp6_parse_coeff_huffman(vp56_context_t *s);
  42
  43 static int vp6_parse_header(vp56_context_t *s, const uint8_t *buf, int buf_size,
  44                             int *golden_frame)
  45 {
  46     vp56_range_coder_t *c = &s->c;
  47     int parse_filter_info = 0;
  48     int coeff_offset = 0;
  49     int vrt_shift = 0;
  50     int sub_version;
  51     int rows, cols;
  52     int res = 1;
  53     int separated_coeff = buf[0] & 1;
  54
  55     s->framep[VP56_FRAME_CURRENT]->key_frame = !(buf[0] & 0x80);
  56     vp56_init_dequant(s, (buf[0] >> 1) & 0x3F);
  57
  58     if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
  59         sub_version = buf[1] >> 3;
  60         if (sub_version > 8)
  61             return 0;
  62         s->filter_header = buf[1] & 0x06;
  63         if (buf[1] & 1) {
  64             av_log(s->avctx, AV_LOG_ERROR, "interlacing not supported\n");
  65             return 0;
  66         }
  67         if (separated_coeff || !s->filter_header) {
  68             coeff_offset = AV_RB16(buf+2) - 2;
  69             buf += 2;
  70             buf_size -= 2;
  71         }
  72
  73         rows = buf[2];  /* number of stored macroblock rows */
  74         cols = buf[3];  /* number of stored macroblock cols */
  75         /* buf[4] is number of displayed macroblock rows */
  76         /* buf[5] is number of displayed macroblock cols */
  77
  78         if (16*cols != s->avctx->coded_width ||
  79             16*rows != s->avctx->coded_height) {
  80             avcodec_set_dimensions(s->avctx, 16*cols, 16*rows);
  81             if (s->avctx->extradata_size == 1) {
  82                 s->avctx->width  -= s->avctx->extradata[0] >> 4;
  83                 s->avctx->height -= s->avctx->extradata[0] & 0x0F;
  84             }
  85             res = 2;
  86         }
  87
  88         vp56_init_range_decoder(c, buf+6, buf_size-6);
  89         vp56_rac_gets(c, 2);
  90
  91         parse_filter_info = s->filter_header;
  92         if (sub_version < 8)
  93             vrt_shift = 5;
  94         s->sub_version = sub_version;
  95     } else {
  96         if (!s->sub_version)
  97             return 0;
  98
  99         if (separated_coeff || !s->filter_header) {
 100             coeff_offset = AV_RB16(buf+1) - 2;
 101             buf += 2;
 102             buf_size -= 2;
 103         }
 104         vp56_init_range_decoder(c, buf+1, buf_size-1);
 105
 106         *golden_frame = vp56_rac_get(c);
 107         if (s->filter_header) {
 108             s->deblock_filtering = vp56_rac_get(c);
 109             if (s->deblock_filtering)
 110                 vp56_rac_get(c);
 111             if (s->sub_version > 7)
 112                 parse_filter_info = vp56_rac_get(c);
 113         }
 114     }
 115
 116     if (parse_filter_info) {
 117         if (vp56_rac_get(c)) {
 118             s->filter_mode = 2;
 119             s->sample_variance_threshold = vp56_rac_gets(c, 5) << vrt_shift;
 120             s->max_vector_length = 2 << vp56_rac_gets(c, 3);
 121         } else if (vp56_rac_get(c)) {
 122             s->filter_mode = 1;
 123         } else {
 124             s->filter_mode = 0;
 125         }
 126         if (s->sub_version > 7)
 127             s->filter_selection = vp56_rac_gets(c, 4);
 128         else
 129             s->filter_selection = 16;
 130     }
 131
 132     s->use_huffman = vp56_rac_get(c);
 133
 134     s->parse_coeff = vp6_parse_coeff;
 135     if (coeff_offset) {
 136         buf      += coeff_offset;
 137         buf_size -= coeff_offset;
 138         if (s->use_huffman) {
 139             s->parse_coeff = vp6_parse_coeff_huffman;
 140             init_get_bits(&s->gb, buf, buf_size<<3);
 141         } else {
 142             vp56_init_range_decoder(&s->cc, buf, buf_size);
 143             s->ccp = &s->cc;
 144         }
 145     } else {
 146         s->ccp = &s->c;
 147     }
 148
 149     return res;
 150 }
 151
 152 static void vp6_coeff_order_table_init(vp56_context_t *s)
 153 {
 154     int i, pos, idx = 1;
 155
 156     s->modelp->coeff_index_to_pos[0] = 0;
 157     for (i=0; i<16; i++)
 158         for (pos=1; pos<64; pos++)
 159             if (s->modelp->coeff_reorder[pos] == i)
 160                 s->modelp->coeff_index_to_pos[idx++] = pos;
 161 }
 162
 163 static void vp6_default_models_init(vp56_context_t *s)
 164 {
 165     vp56_model_t *model = s->modelp;
 166
 167     model->vector_dct[0] = 0xA2;
 168     model->vector_dct[1] = 0xA4;
 169     model->vector_sig[0] = 0x80;
 170     model->vector_sig[1] = 0x80;
 171
 172     memcpy(model->mb_types_stats, vp56_def_mb_types_stats, sizeof(model->mb_types_stats));
 173     memcpy(model->vector_fdv, vp6_def_fdv_vector_model, sizeof(model->vector_fdv));
 174     memcpy(model->vector_pdv, vp6_def_pdv_vector_model, sizeof(model->vector_pdv));
 175     memcpy(model->coeff_runv, vp6_def_runv_coeff_model, sizeof(model->coeff_runv));
 176     memcpy(model->coeff_reorder, vp6_def_coeff_reorder, sizeof(model->coeff_reorder));
 177
 178     vp6_coeff_order_table_init(s);
 179 }
 180
 181 static void vp6_parse_vector_models(vp56_context_t *s)
 182 {
 183     vp56_range_coder_t *c = &s->c;
 184     vp56_model_t *model = s->modelp;
 185     int comp, node;
 186
 187     for (comp=0; comp<2; comp++) {
 188         if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][0]))
 189             model->vector_dct[comp] = vp56_rac_gets_nn(c, 7);
 190         if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][1]))
 191             model->vector_sig[comp] = vp56_rac_gets_nn(c, 7);
 192     }
 193
 194     for (comp=0; comp<2; comp++)
 195         for (node=0; node<7; node++)
 196             if (vp56_rac_get_prob(c, vp6_pdv_pct[comp][node]))
 197                 model->vector_pdv[comp][node] = vp56_rac_gets_nn(c, 7);
 198
 199     for (comp=0; comp<2; comp++)
 200         for (node=0; node<8; node++)
 201             if (vp56_rac_get_prob(c, vp6_fdv_pct[comp][node]))
 202                 model->vector_fdv[comp][node] = vp56_rac_gets_nn(c, 7);
 203 }
 204
 205 /* nodes must ascend by count, but with descending symbol order */
 206 static int vp6_huff_cmp(const void *va, const void *vb)
 207 {
 208     const Node *a = va, *b = vb;
 209     return (a->count - b->count)*16 + (b->sym - a->sym);
 210 }
 211
 212 static void vp6_build_huff_tree(vp56_context_t *s, uint8_t coeff_model[],
 213                                 const uint8_t *map, unsigned size, VLC *vlc)
 214 {
 215     Node nodes[2*size], *tmp = &nodes[size];
 216     int a, b, i;
 217
 218     /* first compute probabilities from model */
 219     tmp[0].count = 256;
 220     for (i=0; i<size-1; i++) {
 221         a = tmp[i].count *        coeff_model[i]  >> 8;
 222         b = tmp[i].count * (255 - coeff_model[i]) >> 8;
 223         nodes[map[2*i  ]].count = a + !a;
 224         nodes[map[2*i+1]].count = b + !b;
 225     }
 226
 227     /* then build the huffman tree accodring to probabilities */
 228     ff_huff_build_tree(s->avctx, vlc, size, nodes, vp6_huff_cmp,
 229                        FF_HUFFMAN_FLAG_HNODE_FIRST);
 230 }
 231
 232 static void vp6_parse_coeff_models(vp56_context_t *s)
 233 {
 234     vp56_range_coder_t *c = &s->c;
 235     vp56_model_t *model = s->modelp;
 236     int def_prob[11];
 237     int node, cg, ctx, pos;
 238     int ct;    /* code type */
 239     int pt;    /* plane type (0 for Y, 1 for U or V) */
 240
 241     memset(def_prob, 0x80, sizeof(def_prob));
 242
 243     for (pt=0; pt<2; pt++)
 244         for (node=0; node<11; node++)
 245             if (vp56_rac_get_prob(c, vp6_dccv_pct[pt][node])) {
 246                 def_prob[node] = vp56_rac_gets_nn(c, 7);
 247                 model->coeff_dccv[pt][node] = def_prob[node];
 248             } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
 249                 model->coeff_dccv[pt][node] = def_prob[node];
 250             }
 251
 252     if (vp56_rac_get(c)) {
 253         for (pos=1; pos<64; pos++)
 254             if (vp56_rac_get_prob(c, vp6_coeff_reorder_pct[pos]))
 255                 model->coeff_reorder[pos] = vp56_rac_gets(c, 4);
 256         vp6_coeff_order_table_init(s);
 257     }
 258
 259     for (cg=0; cg<2; cg++)
 260         for (node=0; node<14; node++)
 261             if (vp56_rac_get_prob(c, vp6_runv_pct[cg][node]))
 262                 model->coeff_runv[cg][node] = vp56_rac_gets_nn(c, 7);
 263
 264     for (ct=0; ct<3; ct++)
 265         for (pt=0; pt<2; pt++)
 266             for (cg=0; cg<6; cg++)
 267                 for (node=0; node<11; node++)
 268                     if (vp56_rac_get_prob(c, vp6_ract_pct[ct][pt][cg][node])) {
 269                         def_prob[node] = vp56_rac_gets_nn(c, 7);
 270                         model->coeff_ract[pt][ct][cg][node] = def_prob[node];
 271                     } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
 272                         model->coeff_ract[pt][ct][cg][node] = def_prob[node];
 273                     }
 274
 275     if (s->use_huffman) {
 276         for (pt=0; pt<2; pt++) {
 277             vp6_build_huff_tree(s, model->coeff_dccv[pt],
 278                                 vp6_huff_coeff_map, 12, &s->dccv_vlc[pt]);
 279             vp6_build_huff_tree(s, model->coeff_runv[pt],
 280                                 vp6_huff_run_map, 9, &s->runv_vlc[pt]);
 281             for (ct=0; ct<3; ct++)
 282                 for (cg = 0; cg < 6; cg++)
 283                     vp6_build_huff_tree(s, model->coeff_ract[pt][ct][cg],
 284                                         vp6_huff_coeff_map, 12,
 285                                         &s->ract_vlc[pt][ct][cg]);
 286         }
 287         memset(s->nb_null, 0, sizeof(s->nb_null));
 288     } else {
 289     /* coeff_dcct is a linear combination of coeff_dccv */
 290     for (pt=0; pt<2; pt++)
 291         for (ctx=0; ctx<3; ctx++)
 292             for (node=0; node<5; node++)
 293                 model->coeff_dcct[pt][ctx][node] = av_clip(((model->coeff_dccv[pt][node] * vp6_dccv_lc[ctx][node][0] + 128) >> 8) + vp6_dccv_lc[ctx][node][1], 1, 255);
 294     }
 295 }
 296
 297 static void vp6_parse_vector_adjustment(vp56_context_t *s, vp56_mv_t *vect)
 298 {
 299     vp56_range_coder_t *c = &s->c;
 300     vp56_model_t *model = s->modelp;
 301     int comp;
 302
 303     *vect = (vp56_mv_t) {0,0};
 304     if (s->vector_candidate_pos < 2)
 305         *vect = s->vector_candidate[0];
 306
 307     for (comp=0; comp<2; comp++) {
 308         int i, delta = 0;
 309
 310         if (vp56_rac_get_prob(c, model->vector_dct[comp])) {
 311             static const uint8_t prob_order[] = {0, 1, 2, 7, 6, 5, 4};
 312             for (i=0; i<sizeof(prob_order); i++) {
 313                 int j = prob_order[i];
 314                 delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][j])<<j;
 315             }
 316             if (delta & 0xF0)
 317                 delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][3])<<3;
 318             else
 319                 delta |= 8;
 320         } else {
 321             delta = vp56_rac_get_tree(c, vp56_pva_tree,
 322                                       model->vector_pdv[comp]);
 323         }
 324
 325         if (delta && vp56_rac_get_prob(c, model->vector_sig[comp]))
 326             delta = -delta;
 327
 328         if (!comp)
 329             vect->x += delta;
 330         else
 331             vect->y += delta;
 332     }
 333 }
 334
 335 /**
 336  * Read number of consecutive blocks with null DC or AC.
 337  * This value is < 74.
 338  */
 339 static unsigned vp6_get_nb_null(vp56_context_t *s)
 340 {
 341     unsigned val = get_bits(&s->gb, 2);
 342     if (val == 2)
 343         val += get_bits(&s->gb, 2);
 344     else if (val == 3) {
 345         val = get_bits1(&s->gb) << 2;
 346         val = 6+val + get_bits(&s->gb, 2+val);
 347     }
 348     return val;
 349 }
 350
 351 static void vp6_parse_coeff_huffman(vp56_context_t *s)
 352 {
 353     vp56_model_t *model = s->modelp;
 354     uint8_t *permute = s->scantable.permutated;
 355     VLC *vlc_coeff;
 356     int coeff, sign, coeff_idx;
 357     int b, cg, idx;
 358     int pt = 0;    /* plane type (0 for Y, 1 for U or V) */
 359
 360     for (b=0; b<6; b++) {
 361         int ct = 0;    /* code type */
 362         if (b > 3) pt = 1;
 363         vlc_coeff = &s->dccv_vlc[pt];
 364
 365         for (coeff_idx=0; coeff_idx<64; ) {
 366             int run = 1;
 367             if (coeff_idx<2 && s->nb_null[coeff_idx][pt]) {
 368                 s->nb_null[coeff_idx][pt]--;
 369                 if (coeff_idx)
 370                     break;
 371             } else {
 372                 coeff = get_vlc2(&s->gb, vlc_coeff->table, 9, 3);
 373                 if (coeff == 0) {
 374                     if (coeff_idx) {
 375                         int pt = (coeff_idx >= 6);
 376                         run += get_vlc2(&s->gb, s->runv_vlc[pt].table, 9, 3);
 377                         if (run >= 9)
 378                             run += get_bits(&s->gb, 6);
 379                     } else
 380                         s->nb_null[0][pt] = vp6_get_nb_null(s);
 381                     ct = 0;
 382                 } else if (coeff == 11) {  /* end of block */
 383                     if (coeff_idx == 1)    /* first AC coeff ? */
 384                         s->nb_null[1][pt] = vp6_get_nb_null(s);
 385                     break;
 386                 } else {
 387                     int coeff2 = vp56_coeff_bias[coeff];
 388                     if (coeff > 4)
 389                         coeff2 += get_bits(&s->gb, coeff <= 9 ? coeff - 4 : 11);
 390                     ct = 1 + (coeff2 > 1);
 391                     sign = get_bits1(&s->gb);
 392                     coeff2 = (coeff2 ^ -sign) + sign;
 393                     if (coeff_idx)
 394                         coeff2 *= s->dequant_ac;
 395                     idx = model->coeff_index_to_pos[coeff_idx];
 396                     s->block_coeff[b][permute[idx]] = coeff2;
 397                 }
 398             }
 399             coeff_idx+=run;
 400             cg = FFMIN(vp6_coeff_groups[coeff_idx], 3);
 401             vlc_coeff = &s->ract_vlc[pt][ct][cg];
 402         }
 403     }
 404 }
 405
 406 static void vp6_parse_coeff(vp56_context_t *s)
 407 {
 408     vp56_range_coder_t *c = s->ccp;
 409     vp56_model_t *model = s->modelp;
 410     uint8_t *permute = s->scantable.permutated;
 411     uint8_t *model1, *model2, *model3;
 412     int coeff, sign, coeff_idx;
 413     int b, i, cg, idx, ctx;
 414     int pt = 0;    /* plane type (0 for Y, 1 for U or V) */
 415
 416     for (b=0; b<6; b++) {
 417         int ct = 1;    /* code type */
 418         int run = 1;
 419
 420         if (b > 3) pt = 1;
 421
 422         ctx = s->left_block[vp56_b6to4[b]].not_null_dc
 423               + s->above_blocks[s->above_block_idx[b]].not_null_dc;
 424         model1 = model->coeff_dccv[pt];
 425         model2 = model->coeff_dcct[pt][ctx];
 426
 427         for (coeff_idx=0; coeff_idx<64; ) {
 428             if ((coeff_idx>1 && ct==0) || vp56_rac_get_prob(c, model2[0])) {
 429                 /* parse a coeff */
 430                 if (vp56_rac_get_prob(c, model2[2])) {
 431                     if (vp56_rac_get_prob(c, model2[3])) {
 432                         idx = vp56_rac_get_tree(c, vp56_pc_tree, model1);
 433                         coeff = vp56_coeff_bias[idx+5];
 434                         for (i=vp56_coeff_bit_length[idx]; i>=0; i--)
 435                             coeff += vp56_rac_get_prob(c, vp56_coeff_parse_table[idx][i]) << i;
 436                     } else {
 437                         if (vp56_rac_get_prob(c, model2[4]))
 438                             coeff = 3 + vp56_rac_get_prob(c, model1[5]);
 439                         else
 440                             coeff = 2;
 441                     }
 442                     ct = 2;
 443                 } else {
 444                     ct = 1;
 445                     coeff = 1;
 446                 }
 447                 sign = vp56_rac_get(c);
 448                 coeff = (coeff ^ -sign) + sign;
 449                 if (coeff_idx)
 450                     coeff *= s->dequant_ac;
 451                 idx = model->coeff_index_to_pos[coeff_idx];
 452                 s->block_coeff[b][permute[idx]] = coeff;
 453                 run = 1;
 454             } else {
 455                 /* parse a run */
 456                 ct = 0;
 457                 if (coeff_idx > 0) {
 458                     if (!vp56_rac_get_prob(c, model2[1]))
 459                         break;
 460
 461                     model3 = model->coeff_runv[coeff_idx >= 6];
 462                     run = vp56_rac_get_tree(c, vp6_pcr_tree, model3);
 463                     if (!run)
 464                         for (run=9, i=0; i<6; i++)
 465                             run += vp56_rac_get_prob(c, model3[i+8]) << i;
 466                 }
 467             }
 468
 469             cg = vp6_coeff_groups[coeff_idx+=run];
 470             model1 = model2 = model->coeff_ract[pt][ct][cg];
 471         }
 472
 473         s->left_block[vp56_b6to4[b]].not_null_dc =
 474         s->above_blocks[s->above_block_idx[b]].not_null_dc = !!s->block_coeff[b][0];
 475     }
 476 }
 477
 478 static int vp6_adjust(int v, int t)
 479 {
 480     int V = v, s = v >> 31;
 481     V ^= s;
 482     V -= s;
 483     if (V-t-1 >= (unsigned)(t-1))
 484         return v;
 485     V = 2*t - V;
 486     V += s;
 487     V ^= s;
 488     return V;
 489 }
 490
 491 static int vp6_block_variance(uint8_t *src, int stride)
 492 {
 493     int sum = 0, square_sum = 0;
 494     int y, x;
 495
 496     for (y=0; y<8; y+=2) {
 497         for (x=0; x<8; x+=2) {
 498             sum += src[x];
 499             square_sum += src[x]*src[x];
 500         }
 501         src += 2*stride;
 502     }
 503     return (16*square_sum - sum*sum) >> 8;
 504 }
 505
 506 static void vp6_filter_hv4(uint8_t *dst, uint8_t *src, int stride,
 507                            int delta, const int16_t *weights)
 508 {
 509     int x, y;
 510
 511     for (y=0; y<8; y++) {
 512         for (x=0; x<8; x++) {
 513             dst[x] = av_clip_uint8((  src[x-delta  ] * weights[0]
 514                                  + src[x        ] * weights[1]
 515                                  + src[x+delta  ] * weights[2]
 516                                  + src[x+2*delta] * weights[3] + 64) >> 7);
 517         }
 518         src += stride;
 519         dst += stride;
 520     }
 521 }
 522
 523 static void vp6_filter_diag2(vp56_context_t *s, uint8_t *dst, uint8_t *src,
 524                              int stride, int h_weight, int v_weight)
 525 {
 526     uint8_t *tmp = s->edge_emu_buffer+16;
 527     s->dsp.put_h264_chroma_pixels_tab[0](tmp, src, stride, 9, h_weight, 0);
 528     s->dsp.put_h264_chroma_pixels_tab[0](dst, tmp, stride, 8, 0, v_weight);
 529 }
 530
 531 static void vp6_filter_diag4(uint8_t *dst, uint8_t *src, int stride,
 532                              const int16_t *h_weights,const int16_t *v_weights)
 533 {
 534     int x, y;
 535     int tmp[8*11];
 536     int *t = tmp;
 537
 538     src -= stride;
 539
 540     for (y=0; y<11; y++) {
 541         for (x=0; x<8; x++) {
 542             t[x] = av_clip_uint8((  src[x-1] * h_weights[0]
 543                                + src[x  ] * h_weights[1]
 544                                + src[x+1] * h_weights[2]
 545                                + src[x+2] * h_weights[3] + 64) >> 7);
 546         }
 547         src += stride;
 548         t += 8;
 549     }
 550
 551     t = tmp + 8;
 552     for (y=0; y<8; y++) {
 553         for (x=0; x<8; x++) {
 554             dst[x] = av_clip_uint8((  t[x-8 ] * v_weights[0]
 555                                  + t[x   ] * v_weights[1]
 556                                  + t[x+8 ] * v_weights[2]
 557                                  + t[x+16] * v_weights[3] + 64) >> 7);
 558         }
 559         dst += stride;
 560         t += 8;
 561     }
 562 }
 563
 564 static void vp6_filter(vp56_context_t *s, uint8_t *dst, uint8_t *src,
 565                        int offset1, int offset2, int stride,
 566                        vp56_mv_t mv, int mask, int select, int luma)
 567 {
 568     int filter4 = 0;
 569     int x8 = mv.x & mask;
 570     int y8 = mv.y & mask;
 571
 572     if (luma) {
 573         x8 *= 2;
 574         y8 *= 2;
 575         filter4 = s->filter_mode;
 576         if (filter4 == 2) {
 577             if (s->max_vector_length &&
 578                 (FFABS(mv.x) > s->max_vector_length ||
 579                  FFABS(mv.y) > s->max_vector_length)) {
 580                 filter4 = 0;
 581             } else if (s->sample_variance_threshold
 582                        && (vp6_block_variance(src+offset1, stride)
 583                            < s->sample_variance_threshold)) {
 584                 filter4 = 0;
 585             }
 586         }
 587     }
 588
 589     if ((y8 && (offset2-offset1)*s->flip<0) || (!y8 && offset1 > offset2)) {
 590         offset1 = offset2;
 591     }
 592
 593     if (filter4) {
 594         if (!y8) {                      /* left or right combine */
 595             vp6_filter_hv4(dst, src+offset1, stride, 1,
 596                            vp6_block_copy_filter[select][x8]);
 597         } else if (!x8) {               /* above or below combine */
 598             vp6_filter_hv4(dst, src+offset1, stride, stride,
 599                            vp6_block_copy_filter[select][y8]);
 600         } else {
 601             vp6_filter_diag4(dst, src+offset1 + ((mv.x^mv.y)>>31), stride,
 602                              vp6_block_copy_filter[select][x8],
 603                              vp6_block_copy_filter[select][y8]);
 604         }
 605     } else {
 606         if (!x8 || !y8) {
 607             s->dsp.put_h264_chroma_pixels_tab[0](dst, src+offset1, stride, 8, x8, y8);
 608         } else {
 609             vp6_filter_diag2(s, dst, src+offset1 + ((mv.x^mv.y)>>31), stride, x8, y8);
 610         }
 611     }
 612 }
 613
 614 static av_cold int vp6_decode_init(AVCodecContext *avctx)
 615 {
 616     vp56_context_t *s = avctx->priv_data;
 617
 618     vp56_init(avctx, avctx->codec->id == CODEC_ID_VP6,
 619                      avctx->codec->id == CODEC_ID_VP6A);
 620     s->vp56_coord_div = vp6_coord_div;
 621     s->parse_vector_adjustment = vp6_parse_vector_adjustment;
 622     s->adjust = vp6_adjust;
 623     s->filter = vp6_filter;
 624     s->default_models_init = vp6_default_models_init;
 625     s->parse_vector_models = vp6_parse_vector_models;
 626     s->parse_coeff_models = vp6_parse_coeff_models;
 627     s->parse_header = vp6_parse_header;
 628
 629     return 0;
 630 }
 631
 632 AVCodec vp6_decoder = {
 633     "vp6",
 634     CODEC_TYPE_VIDEO,
 635     CODEC_ID_VP6,
 636     sizeof(vp56_context_t),
 637     vp6_decode_init,
 638     NULL,
 639     vp56_free,
 640     vp56_decode_frame,
 641     CODEC_CAP_DR1,
 642     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6"),
 643 };
 644
 645 /* flash version, not flipped upside-down */
 646 AVCodec vp6f_decoder = {
 647     "vp6f",
 648     CODEC_TYPE_VIDEO,
 649     CODEC_ID_VP6F,
 650     sizeof(vp56_context_t),
 651     vp6_decode_init,
 652     NULL,
 653     vp56_free,
 654     vp56_decode_frame,
 655     CODEC_CAP_DR1,
 656     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6 (Flash version)"),
 657 };
 658
 659 /* flash version, not flipped upside-down, with alpha channel */
 660 AVCodec vp6a_decoder = {
 661     "vp6a",
 662     CODEC_TYPE_VIDEO,
 663     CODEC_ID_VP6A,
 664     sizeof(vp56_context_t),
 665     vp6_decode_init,
 666     NULL,
 667     vp56_free,
 668     vp56_decode_frame,
 669     CODEC_CAP_DR1,
 670     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6 (Flash version, with alpha channel)"),
 671 };