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 (buf_size < 0)
 139             return 0;
 140         if (s->use_huffman) {
 141             s->parse_coeff = vp6_parse_coeff_huffman;
 142             init_get_bits(&s->gb, buf, buf_size<<3);
 143         } else {
 144             vp56_init_range_decoder(&s->cc, buf, buf_size);
 145             s->ccp = &s->cc;
 146         }
 147     } else {
 148         s->ccp = &s->c;
 149     }
 150
 151     return res;
 152 }
 153
 154 static void vp6_coeff_order_table_init(vp56_context_t *s)
 155 {
 156     int i, pos, idx = 1;
 157
 158     s->modelp->coeff_index_to_pos[0] = 0;
 159     for (i=0; i<16; i++)
 160         for (pos=1; pos<64; pos++)
 161             if (s->modelp->coeff_reorder[pos] == i)
 162                 s->modelp->coeff_index_to_pos[idx++] = pos;
 163 }
 164
 165 static void vp6_default_models_init(vp56_context_t *s)
 166 {
 167     vp56_model_t *model = s->modelp;
 168
 169     model->vector_dct[0] = 0xA2;
 170     model->vector_dct[1] = 0xA4;
 171     model->vector_sig[0] = 0x80;
 172     model->vector_sig[1] = 0x80;
 173
 174     memcpy(model->mb_types_stats, vp56_def_mb_types_stats, sizeof(model->mb_types_stats));
 175     memcpy(model->vector_fdv, vp6_def_fdv_vector_model, sizeof(model->vector_fdv));
 176     memcpy(model->vector_pdv, vp6_def_pdv_vector_model, sizeof(model->vector_pdv));
 177     memcpy(model->coeff_runv, vp6_def_runv_coeff_model, sizeof(model->coeff_runv));
 178     memcpy(model->coeff_reorder, vp6_def_coeff_reorder, sizeof(model->coeff_reorder));
 179
 180     vp6_coeff_order_table_init(s);
 181 }
 182
 183 static void vp6_parse_vector_models(vp56_context_t *s)
 184 {
 185     vp56_range_coder_t *c = &s->c;
 186     vp56_model_t *model = s->modelp;
 187     int comp, node;
 188
 189     for (comp=0; comp<2; comp++) {
 190         if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][0]))
 191             model->vector_dct[comp] = vp56_rac_gets_nn(c, 7);
 192         if (vp56_rac_get_prob(c, vp6_sig_dct_pct[comp][1]))
 193             model->vector_sig[comp] = vp56_rac_gets_nn(c, 7);
 194     }
 195
 196     for (comp=0; comp<2; comp++)
 197         for (node=0; node<7; node++)
 198             if (vp56_rac_get_prob(c, vp6_pdv_pct[comp][node]))
 199                 model->vector_pdv[comp][node] = vp56_rac_gets_nn(c, 7);
 200
 201     for (comp=0; comp<2; comp++)
 202         for (node=0; node<8; node++)
 203             if (vp56_rac_get_prob(c, vp6_fdv_pct[comp][node]))
 204                 model->vector_fdv[comp][node] = vp56_rac_gets_nn(c, 7);
 205 }
 206
 207 /* nodes must ascend by count, but with descending symbol order */
 208 static int vp6_huff_cmp(const void *va, const void *vb)
 209 {
 210     const Node *a = va, *b = vb;
 211     return (a->count - b->count)*16 + (b->sym - a->sym);
 212 }
 213
 214 static void vp6_build_huff_tree(vp56_context_t *s, uint8_t coeff_model[],
 215                                 const uint8_t *map, unsigned size, VLC *vlc)
 216 {
 217     Node nodes[2*size], *tmp = &nodes[size];
 218     int a, b, i;
 219
 220     /* first compute probabilities from model */
 221     tmp[0].count = 256;
 222     for (i=0; i<size-1; i++) {
 223         a = tmp[i].count *        coeff_model[i]  >> 8;
 224         b = tmp[i].count * (255 - coeff_model[i]) >> 8;
 225         nodes[map[2*i  ]].count = a + !a;
 226         nodes[map[2*i+1]].count = b + !b;
 227     }
 228
 229     /* then build the huffman tree accodring to probabilities */
 230     ff_huff_build_tree(s->avctx, vlc, size, nodes, vp6_huff_cmp,
 231                        FF_HUFFMAN_FLAG_HNODE_FIRST);
 232 }
 233
 234 static void vp6_parse_coeff_models(vp56_context_t *s)
 235 {
 236     vp56_range_coder_t *c = &s->c;
 237     vp56_model_t *model = s->modelp;
 238     int def_prob[11];
 239     int node, cg, ctx, pos;
 240     int ct;    /* code type */
 241     int pt;    /* plane type (0 for Y, 1 for U or V) */
 242
 243     memset(def_prob, 0x80, sizeof(def_prob));
 244
 245     for (pt=0; pt<2; pt++)
 246         for (node=0; node<11; node++)
 247             if (vp56_rac_get_prob(c, vp6_dccv_pct[pt][node])) {
 248                 def_prob[node] = vp56_rac_gets_nn(c, 7);
 249                 model->coeff_dccv[pt][node] = def_prob[node];
 250             } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
 251                 model->coeff_dccv[pt][node] = def_prob[node];
 252             }
 253
 254     if (vp56_rac_get(c)) {
 255         for (pos=1; pos<64; pos++)
 256             if (vp56_rac_get_prob(c, vp6_coeff_reorder_pct[pos]))
 257                 model->coeff_reorder[pos] = vp56_rac_gets(c, 4);
 258         vp6_coeff_order_table_init(s);
 259     }
 260
 261     for (cg=0; cg<2; cg++)
 262         for (node=0; node<14; node++)
 263             if (vp56_rac_get_prob(c, vp6_runv_pct[cg][node]))
 264                 model->coeff_runv[cg][node] = vp56_rac_gets_nn(c, 7);
 265
 266     for (ct=0; ct<3; ct++)
 267         for (pt=0; pt<2; pt++)
 268             for (cg=0; cg<6; cg++)
 269                 for (node=0; node<11; node++)
 270                     if (vp56_rac_get_prob(c, vp6_ract_pct[ct][pt][cg][node])) {
 271                         def_prob[node] = vp56_rac_gets_nn(c, 7);
 272                         model->coeff_ract[pt][ct][cg][node] = def_prob[node];
 273                     } else if (s->framep[VP56_FRAME_CURRENT]->key_frame) {
 274                         model->coeff_ract[pt][ct][cg][node] = def_prob[node];
 275                     }
 276
 277     if (s->use_huffman) {
 278         for (pt=0; pt<2; pt++) {
 279             vp6_build_huff_tree(s, model->coeff_dccv[pt],
 280                                 vp6_huff_coeff_map, 12, &s->dccv_vlc[pt]);
 281             vp6_build_huff_tree(s, model->coeff_runv[pt],
 282                                 vp6_huff_run_map, 9, &s->runv_vlc[pt]);
 283             for (ct=0; ct<3; ct++)
 284                 for (cg = 0; cg < 6; cg++)
 285                     vp6_build_huff_tree(s, model->coeff_ract[pt][ct][cg],
 286                                         vp6_huff_coeff_map, 12,
 287                                         &s->ract_vlc[pt][ct][cg]);
 288         }
 289         memset(s->nb_null, 0, sizeof(s->nb_null));
 290     } else {
 291     /* coeff_dcct is a linear combination of coeff_dccv */
 292     for (pt=0; pt<2; pt++)
 293         for (ctx=0; ctx<3; ctx++)
 294             for (node=0; node<5; node++)
 295                 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);
 296     }
 297 }
 298
 299 static void vp6_parse_vector_adjustment(vp56_context_t *s, vp56_mv_t *vect)
 300 {
 301     vp56_range_coder_t *c = &s->c;
 302     vp56_model_t *model = s->modelp;
 303     int comp;
 304
 305     *vect = (vp56_mv_t) {0,0};
 306     if (s->vector_candidate_pos < 2)
 307         *vect = s->vector_candidate[0];
 308
 309     for (comp=0; comp<2; comp++) {
 310         int i, delta = 0;
 311
 312         if (vp56_rac_get_prob(c, model->vector_dct[comp])) {
 313             static const uint8_t prob_order[] = {0, 1, 2, 7, 6, 5, 4};
 314             for (i=0; i<sizeof(prob_order); i++) {
 315                 int j = prob_order[i];
 316                 delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][j])<<j;
 317             }
 318             if (delta & 0xF0)
 319                 delta |= vp56_rac_get_prob(c, model->vector_fdv[comp][3])<<3;
 320             else
 321                 delta |= 8;
 322         } else {
 323             delta = vp56_rac_get_tree(c, vp56_pva_tree,
 324                                       model->vector_pdv[comp]);
 325         }
 326
 327         if (delta && vp56_rac_get_prob(c, model->vector_sig[comp]))
 328             delta = -delta;
 329
 330         if (!comp)
 331             vect->x += delta;
 332         else
 333             vect->y += delta;
 334     }
 335 }
 336
 337 /**
 338  * Read number of consecutive blocks with null DC or AC.
 339  * This value is < 74.
 340  */
 341 static unsigned vp6_get_nb_null(vp56_context_t *s)
 342 {
 343     unsigned val = get_bits(&s->gb, 2);
 344     if (val == 2)
 345         val += get_bits(&s->gb, 2);
 346     else if (val == 3) {
 347         val = get_bits1(&s->gb) << 2;
 348         val = 6+val + get_bits(&s->gb, 2+val);
 349     }
 350     return val;
 351 }
 352
 353 static void vp6_parse_coeff_huffman(vp56_context_t *s)
 354 {
 355     vp56_model_t *model = s->modelp;
 356     uint8_t *permute = s->scantable.permutated;
 357     VLC *vlc_coeff;
 358     int coeff, sign, coeff_idx;
 359     int b, cg, idx;
 360     int pt = 0;    /* plane type (0 for Y, 1 for U or V) */
 361
 362     for (b=0; b<6; b++) {
 363         int ct = 0;    /* code type */
 364         if (b > 3) pt = 1;
 365         vlc_coeff = &s->dccv_vlc[pt];
 366
 367         for (coeff_idx=0; coeff_idx<64; ) {
 368             int run = 1;
 369             if (coeff_idx<2 && s->nb_null[coeff_idx][pt]) {
 370                 s->nb_null[coeff_idx][pt]--;
 371                 if (coeff_idx)
 372                     break;
 373             } else {
 374                 coeff = get_vlc2(&s->gb, vlc_coeff->table, 9, 3);
 375                 if (coeff == 0) {
 376                     if (coeff_idx) {
 377                         int pt = (coeff_idx >= 6);
 378                         run += get_vlc2(&s->gb, s->runv_vlc[pt].table, 9, 3);
 379                         if (run >= 9)
 380                             run += get_bits(&s->gb, 6);
 381                     } else
 382                         s->nb_null[0][pt] = vp6_get_nb_null(s);
 383                     ct = 0;
 384                 } else if (coeff == 11) {  /* end of block */
 385                     if (coeff_idx == 1)    /* first AC coeff ? */
 386                         s->nb_null[1][pt] = vp6_get_nb_null(s);
 387                     break;
 388                 } else {
 389                     int coeff2 = vp56_coeff_bias[coeff];
 390                     if (coeff > 4)
 391                         coeff2 += get_bits(&s->gb, coeff <= 9 ? coeff - 4 : 11);
 392                     ct = 1 + (coeff2 > 1);
 393                     sign = get_bits1(&s->gb);
 394                     coeff2 = (coeff2 ^ -sign) + sign;
 395                     if (coeff_idx)
 396                         coeff2 *= s->dequant_ac;
 397                     idx = model->coeff_index_to_pos[coeff_idx];
 398                     s->block_coeff[b][permute[idx]] = coeff2;
 399                 }
 400             }
 401             coeff_idx+=run;
 402             cg = FFMIN(vp6_coeff_groups[coeff_idx], 3);
 403             vlc_coeff = &s->ract_vlc[pt][ct][cg];
 404         }
 405     }
 406 }
 407
 408 static void vp6_parse_coeff(vp56_context_t *s)
 409 {
 410     vp56_range_coder_t *c = s->ccp;
 411     vp56_model_t *model = s->modelp;
 412     uint8_t *permute = s->scantable.permutated;
 413     uint8_t *model1, *model2, *model3;
 414     int coeff, sign, coeff_idx;
 415     int b, i, cg, idx, ctx;
 416     int pt = 0;    /* plane type (0 for Y, 1 for U or V) */
 417
 418     for (b=0; b<6; b++) {
 419         int ct = 1;    /* code type */
 420         int run = 1;
 421
 422         if (b > 3) pt = 1;
 423
 424         ctx = s->left_block[vp56_b6to4[b]].not_null_dc
 425               + s->above_blocks[s->above_block_idx[b]].not_null_dc;
 426         model1 = model->coeff_dccv[pt];
 427         model2 = model->coeff_dcct[pt][ctx];
 428
 429         for (coeff_idx=0; coeff_idx<64; ) {
 430             if ((coeff_idx>1 && ct==0) || vp56_rac_get_prob(c, model2[0])) {
 431                 /* parse a coeff */
 432                 if (vp56_rac_get_prob(c, model2[2])) {
 433                     if (vp56_rac_get_prob(c, model2[3])) {
 434                         idx = vp56_rac_get_tree(c, vp56_pc_tree, model1);
 435                         coeff = vp56_coeff_bias[idx+5];
 436                         for (i=vp56_coeff_bit_length[idx]; i>=0; i--)
 437                             coeff += vp56_rac_get_prob(c, vp56_coeff_parse_table[idx][i]) << i;
 438                     } else {
 439                         if (vp56_rac_get_prob(c, model2[4]))
 440                             coeff = 3 + vp56_rac_get_prob(c, model1[5]);
 441                         else
 442                             coeff = 2;
 443                     }
 444                     ct = 2;
 445                 } else {
 446                     ct = 1;
 447                     coeff = 1;
 448                 }
 449                 sign = vp56_rac_get(c);
 450                 coeff = (coeff ^ -sign) + sign;
 451                 if (coeff_idx)
 452                     coeff *= s->dequant_ac;
 453                 idx = model->coeff_index_to_pos[coeff_idx];
 454                 s->block_coeff[b][permute[idx]] = coeff;
 455                 run = 1;
 456             } else {
 457                 /* parse a run */
 458                 ct = 0;
 459                 if (coeff_idx > 0) {
 460                     if (!vp56_rac_get_prob(c, model2[1]))
 461                         break;
 462
 463                     model3 = model->coeff_runv[coeff_idx >= 6];
 464                     run = vp56_rac_get_tree(c, vp6_pcr_tree, model3);
 465                     if (!run)
 466                         for (run=9, i=0; i<6; i++)
 467                             run += vp56_rac_get_prob(c, model3[i+8]) << i;
 468                 }
 469             }
 470
 471             cg = vp6_coeff_groups[coeff_idx+=run];
 472             model1 = model2 = model->coeff_ract[pt][ct][cg];
 473         }
 474
 475         s->left_block[vp56_b6to4[b]].not_null_dc =
 476         s->above_blocks[s->above_block_idx[b]].not_null_dc = !!s->block_coeff[b][0];
 477     }
 478 }
 479
 480 static int vp6_adjust(int v, int t)
 481 {
 482     int V = v, s = v >> 31;
 483     V ^= s;
 484     V -= s;
 485     if (V-t-1 >= (unsigned)(t-1))
 486         return v;
 487     V = 2*t - V;
 488     V += s;
 489     V ^= s;
 490     return V;
 491 }
 492
 493 static int vp6_block_variance(uint8_t *src, int stride)
 494 {
 495     int sum = 0, square_sum = 0;
 496     int y, x;
 497
 498     for (y=0; y<8; y+=2) {
 499         for (x=0; x<8; x+=2) {
 500             sum += src[x];
 501             square_sum += src[x]*src[x];
 502         }
 503         src += 2*stride;
 504     }
 505     return (16*square_sum - sum*sum) >> 8;
 506 }
 507
 508 static void vp6_filter_hv4(uint8_t *dst, uint8_t *src, int stride,
 509                            int delta, const int16_t *weights)
 510 {
 511     int x, y;
 512
 513     for (y=0; y<8; y++) {
 514         for (x=0; x<8; x++) {
 515             dst[x] = av_clip_uint8((  src[x-delta  ] * weights[0]
 516                                  + src[x        ] * weights[1]
 517                                  + src[x+delta  ] * weights[2]
 518                                  + src[x+2*delta] * weights[3] + 64) >> 7);
 519         }
 520         src += stride;
 521         dst += stride;
 522     }
 523 }
 524
 525 static void vp6_filter_diag2(vp56_context_t *s, uint8_t *dst, uint8_t *src,
 526                              int stride, int h_weight, int v_weight)
 527 {
 528     uint8_t *tmp = s->edge_emu_buffer+16;
 529     s->dsp.put_h264_chroma_pixels_tab[0](tmp, src, stride, 9, h_weight, 0);
 530     s->dsp.put_h264_chroma_pixels_tab[0](dst, tmp, stride, 8, 0, v_weight);
 531 }
 532
 533 static void vp6_filter_diag4(uint8_t *dst, uint8_t *src, int stride,
 534                              const int16_t *h_weights,const int16_t *v_weights)
 535 {
 536     int x, y;
 537     int tmp[8*11];
 538     int *t = tmp;
 539
 540     src -= stride;
 541
 542     for (y=0; y<11; y++) {
 543         for (x=0; x<8; x++) {
 544             t[x] = av_clip_uint8((  src[x-1] * h_weights[0]
 545                                + src[x  ] * h_weights[1]
 546                                + src[x+1] * h_weights[2]
 547                                + src[x+2] * h_weights[3] + 64) >> 7);
 548         }
 549         src += stride;
 550         t += 8;
 551     }
 552
 553     t = tmp + 8;
 554     for (y=0; y<8; y++) {
 555         for (x=0; x<8; x++) {
 556             dst[x] = av_clip_uint8((  t[x-8 ] * v_weights[0]
 557                                  + t[x   ] * v_weights[1]
 558                                  + t[x+8 ] * v_weights[2]
 559                                  + t[x+16] * v_weights[3] + 64) >> 7);
 560         }
 561         dst += stride;
 562         t += 8;
 563     }
 564 }
 565
 566 static void vp6_filter(vp56_context_t *s, uint8_t *dst, uint8_t *src,
 567                        int offset1, int offset2, int stride,
 568                        vp56_mv_t mv, int mask, int select, int luma)
 569 {
 570     int filter4 = 0;
 571     int x8 = mv.x & mask;
 572     int y8 = mv.y & mask;
 573
 574     if (luma) {
 575         x8 *= 2;
 576         y8 *= 2;
 577         filter4 = s->filter_mode;
 578         if (filter4 == 2) {
 579             if (s->max_vector_length &&
 580                 (FFABS(mv.x) > s->max_vector_length ||
 581                  FFABS(mv.y) > s->max_vector_length)) {
 582                 filter4 = 0;
 583             } else if (s->sample_variance_threshold
 584                        && (vp6_block_variance(src+offset1, stride)
 585                            < s->sample_variance_threshold)) {
 586                 filter4 = 0;
 587             }
 588         }
 589     }
 590
 591     if ((y8 && (offset2-offset1)*s->flip<0) || (!y8 && offset1 > offset2)) {
 592         offset1 = offset2;
 593     }
 594
 595     if (filter4) {
 596         if (!y8) {                      /* left or right combine */
 597             vp6_filter_hv4(dst, src+offset1, stride, 1,
 598                            vp6_block_copy_filter[select][x8]);
 599         } else if (!x8) {               /* above or below combine */
 600             vp6_filter_hv4(dst, src+offset1, stride, stride,
 601                            vp6_block_copy_filter[select][y8]);
 602         } else {
 603             vp6_filter_diag4(dst, src+offset1 + ((mv.x^mv.y)>>31), stride,
 604                              vp6_block_copy_filter[select][x8],
 605                              vp6_block_copy_filter[select][y8]);
 606         }
 607     } else {
 608         if (!x8 || !y8) {
 609             s->dsp.put_h264_chroma_pixels_tab[0](dst, src+offset1, stride, 8, x8, y8);
 610         } else {
 611             vp6_filter_diag2(s, dst, src+offset1 + ((mv.x^mv.y)>>31), stride, x8, y8);
 612         }
 613     }
 614 }
 615
 616 static av_cold int vp6_decode_init(AVCodecContext *avctx)
 617 {
 618     vp56_context_t *s = avctx->priv_data;
 619
 620     vp56_init(avctx, avctx->codec->id == CODEC_ID_VP6,
 621                      avctx->codec->id == CODEC_ID_VP6A);
 622     s->vp56_coord_div = vp6_coord_div;
 623     s->parse_vector_adjustment = vp6_parse_vector_adjustment;
 624     s->adjust = vp6_adjust;
 625     s->filter = vp6_filter;
 626     s->default_models_init = vp6_default_models_init;
 627     s->parse_vector_models = vp6_parse_vector_models;
 628     s->parse_coeff_models = vp6_parse_coeff_models;
 629     s->parse_header = vp6_parse_header;
 630
 631     return 0;
 632 }
 633
 634 AVCodec vp6_decoder = {
 635     "vp6",
 636     CODEC_TYPE_VIDEO,
 637     CODEC_ID_VP6,
 638     sizeof(vp56_context_t),
 639     vp6_decode_init,
 640     NULL,
 641     vp56_free,
 642     vp56_decode_frame,
 643     CODEC_CAP_DR1,
 644     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6"),
 645 };
 646
 647 /* flash version, not flipped upside-down */
 648 AVCodec vp6f_decoder = {
 649     "vp6f",
 650     CODEC_TYPE_VIDEO,
 651     CODEC_ID_VP6F,
 652     sizeof(vp56_context_t),
 653     vp6_decode_init,
 654     NULL,
 655     vp56_free,
 656     vp56_decode_frame,
 657     CODEC_CAP_DR1,
 658     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6 (Flash version)"),
 659 };
 660
 661 /* flash version, not flipped upside-down, with alpha channel */
 662 AVCodec vp6a_decoder = {
 663     "vp6a",
 664     CODEC_TYPE_VIDEO,
 665     CODEC_ID_VP6A,
 666     sizeof(vp56_context_t),
 667     vp6_decode_init,
 668     NULL,
 669     vp56_free,
 670     vp56_decode_frame,
 671     CODEC_CAP_DR1,
 672     .long_name = NULL_IF_CONFIG_SMALL("On2 VP6 (Flash version, with alpha channel)"),
 673 };