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