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FFmpeg/libavcodec/cavsdec.c

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  1. /*

  2.  * Chinese AVS video (AVS1-P2, JiZhun profile) decoder.

  3.  * Copyright (c) 2006  Stefan Gehrer <stefan.gehrer@gmx.de>

  4.  *

  5.  * This file is part of FFmpeg.

  6.  *

  7.  * FFmpeg is free software; you can redistribute it and/or

  8.  * modify it under the terms of the GNU Lesser General Public

  9.  * License as published by the Free Software Foundation; either

  10.  * version 2.1 of the License, or (at your option) any later version.

  11.  *

  12.  * FFmpeg is distributed in the hope that it will be useful,

  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  15.  * Lesser General Public License for more details.

  16.  *

  17.  * You should have received a copy of the GNU Lesser General Public

  18.  * License along with FFmpeg; if not, write to the Free Software

  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  20.  */

  21. 

  22. /**

  23.  * @file

  24.  * Chinese AVS video (AVS1-P2, JiZhun profile) decoder

  25.  * @author Stefan Gehrer <stefan.gehrer@gmx.de>

  26.  */

  27. 

  28. #include "avcodec.h"

  29. #include "get_bits.h"

  30. #include "golomb.h"

  31. #include "cavs.h"

  32. 

  33. static const uint8_t mv_scan[4] = {

  34.     MV_FWD_X0,MV_FWD_X1,

  35.     MV_FWD_X2,MV_FWD_X3

  36. };

  37. 

  38. static const uint8_t cbp_tab[64][2] = {

  39.   {63, 0},{15,15},{31,63},{47,31},{ 0,16},{14,32},{13,47},{11,13},

  40.   { 7,14},{ 5,11},{10,12},{ 8, 5},{12,10},{61, 7},{ 4,48},{55, 3},

  41.   { 1, 2},{ 2, 8},{59, 4},{ 3, 1},{62,61},{ 9,55},{ 6,59},{29,62},

  42.   {45,29},{51,27},{23,23},{39,19},{27,30},{46,28},{53, 9},{30, 6},

  43.   {43,60},{37,21},{60,44},{16,26},{21,51},{28,35},{19,18},{35,20},

  44.   {42,24},{26,53},{44,17},{32,37},{58,39},{24,45},{20,58},{17,43},

  45.   {18,42},{48,46},{22,36},{33,33},{25,34},{49,40},{40,52},{36,49},

  46.   {34,50},{50,56},{52,25},{54,22},{41,54},{56,57},{38,41},{57,38}

  47. };

  48. 

  49. /*****************************************************************************

  50.  *

  51.  * motion vector prediction

  52.  *

  53.  ****************************************************************************/

  54. 

  55. static inline void store_mvs(AVSContext *h) {

  56.     h->col_mv[h->mbidx*4 + 0] = h->mv[MV_FWD_X0];

  57.     h->col_mv[h->mbidx*4 + 1] = h->mv[MV_FWD_X1];

  58.     h->col_mv[h->mbidx*4 + 2] = h->mv[MV_FWD_X2];

  59.     h->col_mv[h->mbidx*4 + 3] = h->mv[MV_FWD_X3];

  60. }

  61. 

  62. static inline void mv_pred_direct(AVSContext *h, cavs_vector *pmv_fw,

  63.                                   cavs_vector *col_mv) {

  64.     cavs_vector *pmv_bw = pmv_fw + MV_BWD_OFFS;

  65.     int den = h->direct_den[col_mv->ref];

  66.     int m = col_mv->x >> 31;

  67. 

  68.     pmv_fw->dist = h->dist[1];

  69.     pmv_bw->dist = h->dist[0];

  70.     pmv_fw->ref = 1;

  71.     pmv_bw->ref = 0;

  72.     /* scale the co-located motion vector according to its temporal span */

  73.     pmv_fw->x = (((den+(den*col_mv->x*pmv_fw->dist^m)-m-1)>>14)^m)-m;

  74.     pmv_bw->x = m-(((den+(den*col_mv->x*pmv_bw->dist^m)-m-1)>>14)^m);

  75.     m = col_mv->y >> 31;

  76.     pmv_fw->y = (((den+(den*col_mv->y*pmv_fw->dist^m)-m-1)>>14)^m)-m;

  77.     pmv_bw->y = m-(((den+(den*col_mv->y*pmv_bw->dist^m)-m-1)>>14)^m);

  78. }

  79. 

  80. static inline void mv_pred_sym(AVSContext *h, cavs_vector *src, enum cavs_block size) {

  81.     cavs_vector *dst = src + MV_BWD_OFFS;

  82. 

  83.     /* backward mv is the scaled and negated forward mv */

  84.     dst->x = -((src->x * h->sym_factor + 256) >> 9);

  85.     dst->y = -((src->y * h->sym_factor + 256) >> 9);

  86.     dst->ref = 0;

  87.     dst->dist = h->dist[0];

  88.     set_mvs(dst, size);

  89. }

  90. 

  91. /*****************************************************************************

  92.  *

  93.  * residual data decoding

  94.  *

  95.  ****************************************************************************/

  96. 

  97. /** kth-order exponential golomb code */

  98. static inline int get_ue_code(GetBitContext *gb, int order) {

  99.     if(order) {

  100.         int ret = get_ue_golomb(gb) << order;

  101.         return ret + get_bits(gb,order);

  102.     }

  103.     return get_ue_golomb(gb);

  104. }

  105. 

  106. /**

  107.  * decode coefficients from one 8x8 block, dequantize, inverse transform

  108.  *  and add them to sample block

  109.  * @param r pointer to 2D VLC table

  110.  * @param esc_golomb_order escape codes are k-golomb with this order k

  111.  * @param qp quantizer

  112.  * @param dst location of sample block

  113.  * @param stride line stride in frame buffer

  114.  */

  115. static int decode_residual_block(AVSContext *h, GetBitContext *gb,

  116.                                  const struct dec_2dvlc *r, int esc_golomb_order,

  117.                                  int qp, uint8_t *dst, int stride) {

  118.     int i, esc_code, level, mask;

  119.     unsigned int level_code, run;

  120.     DCTELEM level_buf[65];

  121.     uint8_t run_buf[65];

  122.     DCTELEM *block = h->block;

  123. 

  124.     for(i=0;i<65;i++) {

  125.         level_code = get_ue_code(gb,r->golomb_order);

  126.         if(level_code >= ESCAPE_CODE) {

  127.             run = ((level_code - ESCAPE_CODE) >> 1) + 1;

  128.             if(run > 64)

  129.                 return -1;

  130.             esc_code = get_ue_code(gb,esc_golomb_order);

  131.             level = esc_code + (run > r->max_run ? 1 : r->level_add[run]);

  132.             while(level > r->inc_limit)

  133.                 r++;

  134.             mask = -(level_code & 1);

  135.             level = (level^mask) - mask;

  136.         } else {

  137.             level = r->rltab[level_code][0];

  138.             if(!level) //end of block signal

  139.                 break;

  140.             run   = r->rltab[level_code][1];

  141.             r += r->rltab[level_code][2];

  142.         }

  143.         level_buf[i] = level;

  144.         run_buf[i] = run;

  145.     }

  146.     if(dequant(h,level_buf, run_buf, block, ff_cavs_dequant_mul[qp],

  147.                ff_cavs_dequant_shift[qp], i))

  148.         return -1;

  149.     h->cdsp.cavs_idct8_add(dst,block,stride);

  150.     h->s.dsp.clear_block(block);

  151.     return 0;

  152. }

  153. 

  154. 

  155. static inline void decode_residual_chroma(AVSContext *h) {

  156.     if(h->cbp & (1<<4))

  157.         decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,

  158.                               ff_cavs_chroma_qp[h->qp],h->cu,h->c_stride);

  159.     if(h->cbp & (1<<5))

  160.         decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,

  161.                               ff_cavs_chroma_qp[h->qp],h->cv,h->c_stride);

  162. }

  163. 

  164. static inline int decode_residual_inter(AVSContext *h) {

  165.     int block;

  166. 

  167.     /* get coded block pattern */

  168.     int cbp= get_ue_golomb(&h->s.gb);

  169.     if(cbp > 63U){

  170.         av_log(h->s.avctx, AV_LOG_ERROR, "illegal inter cbp\n");

  171.         return -1;

  172.     }

  173.     h->cbp = cbp_tab[cbp][1];

  174. 

  175.     /* get quantizer */

  176.     if(h->cbp && !h->qp_fixed)

  177.         h->qp = (h->qp + get_se_golomb(&h->s.gb)) & 63;

  178.     for(block=0;block<4;block++)

  179.         if(h->cbp & (1<<block))

  180.             decode_residual_block(h,&h->s.gb,ff_cavs_inter_dec,0,h->qp,

  181.                                   h->cy + h->luma_scan[block], h->l_stride);

  182.     decode_residual_chroma(h);

  183. 

  184.     return 0;

  185. }

  186. 

  187. /*****************************************************************************

  188.  *

  189.  * macroblock level

  190.  *

  191.  ****************************************************************************/

  192. 

  193. static int decode_mb_i(AVSContext *h, int cbp_code) {

  194.     GetBitContext *gb = &h->s.gb;

  195.     unsigned pred_mode_uv;

  196.     int block;

  197.     uint8_t top[18];

  198.     uint8_t *left = NULL;

  199.     uint8_t *d;

  200. 

  201.     ff_cavs_init_mb(h);

  202. 

  203.     /* get intra prediction modes from stream */

  204.     for(block=0;block<4;block++) {

  205.         int nA,nB,predpred;

  206.         int pos = ff_cavs_scan3x3[block];

  207. 

  208.         nA = h->pred_mode_Y[pos-1];

  209.         nB = h->pred_mode_Y[pos-3];

  210.         predpred = FFMIN(nA,nB);

  211.         if(predpred == NOT_AVAIL) // if either is not available

  212.             predpred = INTRA_L_LP;

  213.         if(!get_bits1(gb)){

  214.             int rem_mode= get_bits(gb, 2);

  215.             predpred = rem_mode + (rem_mode >= predpred);

  216.         }

  217.         h->pred_mode_Y[pos] = predpred;

  218.     }

  219.     pred_mode_uv = get_ue_golomb(gb);

  220.     if(pred_mode_uv > 6) {

  221.         av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra chroma pred mode\n");

  222.         return -1;

  223.     }

  224.     ff_cavs_modify_mb_i(h, &pred_mode_uv);

  225. 

  226.     /* get coded block pattern */

  227.     if(h->pic_type == AV_PICTURE_TYPE_I)

  228.         cbp_code = get_ue_golomb(gb);

  229.     if(cbp_code > 63U){

  230.         av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra cbp\n");

  231.         return -1;

  232.     }

  233.     h->cbp = cbp_tab[cbp_code][0];

  234.     if(h->cbp && !h->qp_fixed)

  235.         h->qp = (h->qp + get_se_golomb(gb)) & 63; //qp_delta

  236. 

  237.     /* luma intra prediction interleaved with residual decode/transform/add */

  238.     for(block=0;block<4;block++) {

  239.         d = h->cy + h->luma_scan[block];

  240.         ff_cavs_load_intra_pred_luma(h, top, &left, block);

  241.         h->intra_pred_l[h->pred_mode_Y[ff_cavs_scan3x3[block]]]

  242.             (d, top, left, h->l_stride);

  243.         if(h->cbp & (1<<block))

  244.             decode_residual_block(h,gb,ff_cavs_intra_dec,1,h->qp,d,h->l_stride);

  245.     }

  246. 

  247.     /* chroma intra prediction */

  248.     ff_cavs_load_intra_pred_chroma(h);

  249.     h->intra_pred_c[pred_mode_uv](h->cu, &h->top_border_u[h->mbx*10],

  250.                                   h->left_border_u, h->c_stride);

  251.     h->intra_pred_c[pred_mode_uv](h->cv, &h->top_border_v[h->mbx*10],

  252.                                   h->left_border_v, h->c_stride);

  253. 

  254.     decode_residual_chroma(h);

  255.     ff_cavs_filter(h,I_8X8);

  256.     set_mv_intra(h);

  257.     return 0;

  258. }

  259. 

  260. static void decode_mb_p(AVSContext *h, enum cavs_mb mb_type) {

  261.     GetBitContext *gb = &h->s.gb;

  262.     int ref[4];

  263. 

  264.     ff_cavs_init_mb(h);

  265.     switch(mb_type) {

  266.     case P_SKIP:

  267.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_PSKIP,  BLK_16X16, 0);

  268.         break;

  269.     case P_16X16:

  270.         ref[0] = h->ref_flag ? 0 : get_bits1(gb);

  271.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16,ref[0]);

  272.         break;

  273.     case P_16X8:

  274.         ref[0] = h->ref_flag ? 0 : get_bits1(gb);

  275.         ref[2] = h->ref_flag ? 0 : get_bits1(gb);

  276.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,    BLK_16X8, ref[0]);

  277.         ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT,   BLK_16X8, ref[2]);

  278.         break;

  279.     case P_8X16:

  280.         ref[0] = h->ref_flag ? 0 : get_bits1(gb);

  281.         ref[1] = h->ref_flag ? 0 : get_bits1(gb);

  282.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT,   BLK_8X16, ref[0]);

  283.         ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_TOPRIGHT,BLK_8X16, ref[1]);

  284.         break;

  285.     case P_8X8:

  286.         ref[0] = h->ref_flag ? 0 : get_bits1(gb);

  287.         ref[1] = h->ref_flag ? 0 : get_bits1(gb);

  288.         ref[2] = h->ref_flag ? 0 : get_bits1(gb);

  289.         ref[3] = h->ref_flag ? 0 : get_bits1(gb);

  290.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_MEDIAN,   BLK_8X8, ref[0]);

  291.         ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_MEDIAN,   BLK_8X8, ref[1]);

  292.         ff_cavs_mv(h, MV_FWD_X2, MV_FWD_X1, MV_PRED_MEDIAN,   BLK_8X8, ref[2]);

  293.         ff_cavs_mv(h, MV_FWD_X3, MV_FWD_X0, MV_PRED_MEDIAN,   BLK_8X8, ref[3]);

  294.     }

  295.     ff_cavs_inter(h, mb_type);

  296.     set_intra_mode_default(h);

  297.     store_mvs(h);

  298.     if(mb_type != P_SKIP)

  299.         decode_residual_inter(h);

  300.     ff_cavs_filter(h,mb_type);

  301.     h->col_type_base[h->mbidx] = mb_type;

  302. }

  303. 

  304. static void decode_mb_b(AVSContext *h, enum cavs_mb mb_type) {

  305.     int block;

  306.     enum cavs_sub_mb sub_type[4];

  307.     int flags;

  308. 

  309.     ff_cavs_init_mb(h);

  310. 

  311.     /* reset all MVs */

  312.     h->mv[MV_FWD_X0] = ff_cavs_dir_mv;

  313.     set_mvs(&h->mv[MV_FWD_X0], BLK_16X16);

  314.     h->mv[MV_BWD_X0] = ff_cavs_dir_mv;

  315.     set_mvs(&h->mv[MV_BWD_X0], BLK_16X16);

  316.     switch(mb_type) {

  317.     case B_SKIP:

  318.     case B_DIRECT:

  319.         if(!h->col_type_base[h->mbidx]) {

  320.             /* intra MB at co-location, do in-plane prediction */

  321.             ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_BSKIP, BLK_16X16, 1);

  322.             ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_BSKIP, BLK_16X16, 0);

  323.         } else

  324.             /* direct prediction from co-located P MB, block-wise */

  325.             for(block=0;block<4;block++)

  326.                 mv_pred_direct(h,&h->mv[mv_scan[block]],

  327.                                  &h->col_mv[h->mbidx*4 + block]);

  328.         break;

  329.     case B_FWD_16X16:

  330.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);

  331.         break;

  332.     case B_SYM_16X16:

  333.         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);

  334.         mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X16);

  335.         break;

  336.     case B_BWD_16X16:

  337.         ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_MEDIAN, BLK_16X16, 0);

  338.         break;

  339.     case B_8X8:

  340.         for(block=0;block<4;block++)

  341.             sub_type[block] = get_bits(&h->s.gb,2);

  342.         for(block=0;block<4;block++) {

  343.             switch(sub_type[block]) {

  344.             case B_SUB_DIRECT:

  345.                 if(!h->col_type_base[h->mbidx]) {

  346.                     /* intra MB at co-location, do in-plane prediction */

  347.                     ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,

  348.                             MV_PRED_BSKIP, BLK_8X8, 1);

  349.                     ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,

  350.                             mv_scan[block]-3+MV_BWD_OFFS,

  351.                             MV_PRED_BSKIP, BLK_8X8, 0);

  352.                 } else

  353.                     mv_pred_direct(h,&h->mv[mv_scan[block]],

  354.                                    &h->col_mv[h->mbidx*4 + block]);

  355.                 break;

  356.             case B_SUB_FWD:

  357.                 ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,

  358.                         MV_PRED_MEDIAN, BLK_8X8, 1);

  359.                 break;

  360.             case B_SUB_SYM:

  361.                 ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,

  362.                         MV_PRED_MEDIAN, BLK_8X8, 1);

  363.                 mv_pred_sym(h, &h->mv[mv_scan[block]], BLK_8X8);

  364.                 break;

  365.             }

  366.         }

  367.         for(block=0;block<4;block++) {

  368.             if(sub_type[block] == B_SUB_BWD)

  369.                 ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,

  370.                         mv_scan[block]+MV_BWD_OFFS-3,

  371.                         MV_PRED_MEDIAN, BLK_8X8, 0);

  372.         }

  373.         break;

  374.     default:

  375.         assert((mb_type > B_SYM_16X16) && (mb_type < B_8X8));

  376.         flags = ff_cavs_partition_flags[mb_type];

  377.         if(mb_type & 1) { /* 16x8 macroblock types */

  378.             if(flags & FWD0)

  379.                 ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,  BLK_16X8, 1);

  380.             if(flags & SYM0)

  381.                 mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X8);

  382.             if(flags & FWD1)

  383.                 ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT, BLK_16X8, 1);

  384.             if(flags & SYM1)

  385.                 mv_pred_sym(h, &h->mv[MV_FWD_X2], BLK_16X8);

  386.             if(flags & BWD0)

  387.                 ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_TOP,  BLK_16X8, 0);

  388.             if(flags & BWD1)

  389.                 ff_cavs_mv(h, MV_BWD_X2, MV_BWD_A1, MV_PRED_LEFT, BLK_16X8, 0);

  390.         } else {          /* 8x16 macroblock types */

  391.             if(flags & FWD0)

  392.                 ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT, BLK_8X16, 1);

  393.             if(flags & SYM0)

  394.                 mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_8X16);

  395.             if(flags & FWD1)

  396.                 ff_cavs_mv(h,MV_FWD_X1,MV_FWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,1);

  397.             if(flags & SYM1)

  398.                 mv_pred_sym(h, &h->mv[MV_FWD_X1], BLK_8X16);

  399.             if(flags & BWD0)

  400.                 ff_cavs_mv(h, MV_BWD_X0, MV_BWD_B3, MV_PRED_LEFT, BLK_8X16, 0);

  401.             if(flags & BWD1)

  402.                 ff_cavs_mv(h,MV_BWD_X1,MV_BWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,0);

  403.         }

  404.     }

  405.     ff_cavs_inter(h, mb_type);

  406.     set_intra_mode_default(h);

  407.     if(mb_type != B_SKIP)

  408.         decode_residual_inter(h);

  409.     ff_cavs_filter(h,mb_type);

  410. }

  411. 

  412. /*****************************************************************************

  413.  *

  414.  * slice level

  415.  *

  416.  ****************************************************************************/

  417. 

  418. static inline int decode_slice_header(AVSContext *h, GetBitContext *gb) {

  419.     if(h->stc > 0xAF)

  420.         av_log(h->s.avctx, AV_LOG_ERROR, "unexpected start code 0x%02x\n", h->stc);

  421. 

  422.     if (h->stc >= h->mb_height)

  423.         return -1;

  424. 

  425.     h->mby = h->stc;

  426.     h->mbidx = h->mby*h->mb_width;

  427. 

  428.     /* mark top macroblocks as unavailable */

  429.     h->flags &= ~(B_AVAIL|C_AVAIL);

  430.     if((h->mby == 0) && (!h->qp_fixed)){

  431.         h->qp_fixed = get_bits1(gb);

  432.         h->qp = get_bits(gb,6);

  433.     }

  434.     /* inter frame or second slice can have weighting params */

  435.     if((h->pic_type != AV_PICTURE_TYPE_I) || (!h->pic_structure && h->mby >= h->mb_width/2))

  436.         if(get_bits1(gb)) { //slice_weighting_flag

  437.             av_log(h->s.avctx, AV_LOG_ERROR,

  438.                    "weighted prediction not yet supported\n");

  439.         }

  440.     return 0;

  441. }

  442. 

  443. static inline int check_for_slice(AVSContext *h) {

  444.     GetBitContext *gb = &h->s.gb;

  445.     int align;

  446. 

  447.     if(h->mbx)

  448.         return 0;

  449.     align = (-get_bits_count(gb)) & 7;

  450.     /* check for stuffing byte */

  451.     if(!align && (show_bits(gb,8) == 0x80))

  452.         align = 8;

  453.     if((show_bits_long(gb,24+align) & 0xFFFFFF) == 0x000001) {

  454.         skip_bits_long(gb,24+align);

  455.         h->stc = get_bits(gb,8);

  456.         if (h->stc >= h->mb_height)

  457.             return 0;

  458.         decode_slice_header(h,gb);

  459.         return 1;

  460.     }

  461.     return 0;

  462. }

  463. 

  464. /*****************************************************************************

  465.  *

  466.  * frame level

  467.  *

  468.  ****************************************************************************/

  469. 

  470. static int decode_pic(AVSContext *h) {

  471.     MpegEncContext *s = &h->s;

  472.     int skip_count = -1;

  473.     enum cavs_mb mb_type;

  474. 

  475.     if (!s->context_initialized) {

  476.         s->avctx->idct_algo = FF_IDCT_CAVS;

  477.         if (ff_MPV_common_init(s) < 0)

  478.             return -1;

  479.         ff_init_scantable(s->dsp.idct_permutation,&h->scantable,ff_zigzag_direct);

  480.     }

  481.     skip_bits(&s->gb,16);//bbv_dwlay

  482.     if(h->stc == PIC_PB_START_CODE) {

  483.         h->pic_type = get_bits(&s->gb,2) + AV_PICTURE_TYPE_I;

  484.         if(h->pic_type > AV_PICTURE_TYPE_B) {

  485.             av_log(s->avctx, AV_LOG_ERROR, "illegal picture type\n");

  486.             return -1;

  487.         }

  488.         /* make sure we have the reference frames we need */

  489.         if(!h->DPB[0].f.data[0] ||

  490.           (!h->DPB[1].f.data[0] && h->pic_type == AV_PICTURE_TYPE_B))

  491.             return -1;

  492.     } else {

  493.         h->pic_type = AV_PICTURE_TYPE_I;

  494.         if(get_bits1(&s->gb))

  495.             skip_bits(&s->gb,24);//time_code

  496.         /* old sample clips were all progressive and no low_delay,

  497.            bump stream revision if detected otherwise */

  498.         if (s->low_delay || !(show_bits(&s->gb,9) & 1))

  499.             h->stream_revision = 1;

  500.         /* similarly test top_field_first and repeat_first_field */

  501.         else if(show_bits(&s->gb,11) & 3)

  502.             h->stream_revision = 1;

  503.         if(h->stream_revision > 0)

  504.             skip_bits(&s->gb,1); //marker_bit

  505.     }

  506.     /* release last B frame */

  507.     if(h->picture.f.data[0])

  508.         s->avctx->release_buffer(s->avctx, &h->picture.f);

  509. 

  510.     s->avctx->get_buffer(s->avctx, &h->picture.f);

  511.     ff_cavs_init_pic(h);

  512.     h->picture.poc = get_bits(&s->gb,8)*2;

  513. 

  514.     /* get temporal distances and MV scaling factors */

  515.     if(h->pic_type != AV_PICTURE_TYPE_B) {

  516.         h->dist[0] = (h->picture.poc - h->DPB[0].poc  + 512) % 512;

  517.     } else {

  518.         h->dist[0] = (h->DPB[0].poc  - h->picture.poc + 512) % 512;

  519.     }

  520.     h->dist[1] = (h->picture.poc - h->DPB[1].poc  + 512) % 512;

  521.     h->scale_den[0] = h->dist[0] ? 512/h->dist[0] : 0;

  522.     h->scale_den[1] = h->dist[1] ? 512/h->dist[1] : 0;

  523.     if(h->pic_type == AV_PICTURE_TYPE_B) {

  524.         h->sym_factor = h->dist[0]*h->scale_den[1];

  525.     } else {

  526.         h->direct_den[0] = h->dist[0] ? 16384/h->dist[0] : 0;

  527.         h->direct_den[1] = h->dist[1] ? 16384/h->dist[1] : 0;

  528.     }

  529. 

  530.     if(s->low_delay)

  531.         get_ue_golomb(&s->gb); //bbv_check_times

  532.     h->progressive             = get_bits1(&s->gb);

  533.     h->pic_structure = 1;

  534.     if(!h->progressive)

  535.         h->pic_structure = get_bits1(&s->gb);

  536.     if(!h->pic_structure && h->stc == PIC_PB_START_CODE)

  537.         skip_bits1(&s->gb);     //advanced_pred_mode_disable

  538.     skip_bits1(&s->gb);        //top_field_first

  539.     skip_bits1(&s->gb);        //repeat_first_field

  540.     h->qp_fixed                = get_bits1(&s->gb);

  541.     h->qp                      = get_bits(&s->gb,6);

  542.     if(h->pic_type == AV_PICTURE_TYPE_I) {

  543.         if(!h->progressive && !h->pic_structure)

  544.             skip_bits1(&s->gb);//what is this?

  545.         skip_bits(&s->gb,4);   //reserved bits

  546.     } else {

  547.         if(!(h->pic_type == AV_PICTURE_TYPE_B && h->pic_structure == 1))

  548.             h->ref_flag        = get_bits1(&s->gb);

  549.         skip_bits(&s->gb,4);   //reserved bits

  550.         h->skip_mode_flag      = get_bits1(&s->gb);

  551.     }

  552.     h->loop_filter_disable     = get_bits1(&s->gb);

  553.     if(!h->loop_filter_disable && get_bits1(&s->gb)) {

  554.         h->alpha_offset        = get_se_golomb(&s->gb);

  555.         h->beta_offset         = get_se_golomb(&s->gb);

  556.     } else {

  557.         h->alpha_offset = h->beta_offset  = 0;

  558.     }

  559.     if(h->pic_type == AV_PICTURE_TYPE_I) {

  560.         do {

  561.             check_for_slice(h);

  562.             decode_mb_i(h, 0);

  563.         } while(ff_cavs_next_mb(h));

  564.     } else if(h->pic_type == AV_PICTURE_TYPE_P) {

  565.         do {

  566.             if(check_for_slice(h))

  567.                 skip_count = -1;

  568.             if(h->skip_mode_flag && (skip_count < 0))

  569.                 skip_count = get_ue_golomb(&s->gb);

  570.             if(h->skip_mode_flag && skip_count--) {

  571.                 decode_mb_p(h,P_SKIP);

  572.             } else {

  573.                 mb_type = get_ue_golomb(&s->gb) + P_SKIP + h->skip_mode_flag;

  574.                 if(mb_type > P_8X8)

  575.                     decode_mb_i(h, mb_type - P_8X8 - 1);

  576.                 else

  577.                     decode_mb_p(h,mb_type);

  578.             }

  579.         } while(ff_cavs_next_mb(h));

  580.     } else { /* AV_PICTURE_TYPE_B */

  581.         do {

  582.             if(check_for_slice(h))

  583.                 skip_count = -1;

  584.             if(h->skip_mode_flag && (skip_count < 0))

  585.                 skip_count = get_ue_golomb(&s->gb);

  586.             if(h->skip_mode_flag && skip_count--) {

  587.                 decode_mb_b(h,B_SKIP);

  588.             } else {

  589.                 mb_type = get_ue_golomb(&s->gb) + B_SKIP + h->skip_mode_flag;

  590.                 if(mb_type > B_8X8)

  591.                     decode_mb_i(h, mb_type - B_8X8 - 1);

  592.                 else

  593.                     decode_mb_b(h,mb_type);

  594.             }

  595.         } while(ff_cavs_next_mb(h));

  596.     }

  597.     if(h->pic_type != AV_PICTURE_TYPE_B) {

  598.         if(h->DPB[1].f.data[0])

  599.             s->avctx->release_buffer(s->avctx, &h->DPB[1].f);

  600.         h->DPB[1] = h->DPB[0];

  601.         h->DPB[0] = h->picture;

  602.         memset(&h->picture,0,sizeof(Picture));

  603.     }

  604.     return 0;

  605. }

  606. 

  607. /*****************************************************************************

  608.  *

  609.  * headers and interface

  610.  *

  611.  ****************************************************************************/

  612. 

  613. static int decode_seq_header(AVSContext *h) {

  614.     MpegEncContext *s = &h->s;

  615.     int frame_rate_code;

  616.     int width, height;

  617. 

  618.     h->profile =         get_bits(&s->gb,8);

  619.     h->level =           get_bits(&s->gb,8);

  620.     skip_bits1(&s->gb); //progressive sequence

  621.        width =           get_bits(&s->gb,14);

  622.        height =          get_bits(&s->gb,14);

  623.     if ((s->width || s->height) && (s->width != width || s->height != height)) {

  624.         av_log_missing_feature(s, "Width/height changing in CAVS is", 0);

  625.         return -1;

  626.     }

  627.     s->width  = width;

  628.     s->height = height;

  629.     skip_bits(&s->gb,2); //chroma format

  630.     skip_bits(&s->gb,3); //sample_precision

  631.     h->aspect_ratio =    get_bits(&s->gb,4);

  632.     frame_rate_code =    get_bits(&s->gb,4);

  633.     skip_bits(&s->gb,18);//bit_rate_lower

  634.     skip_bits1(&s->gb);  //marker_bit

  635.     skip_bits(&s->gb,12);//bit_rate_upper

  636.     s->low_delay =       get_bits1(&s->gb);

  637.     h->mb_width  = (s->width  + 15) >> 4;

  638.     h->mb_height = (s->height + 15) >> 4;

  639.     h->s.avctx->time_base.den = avpriv_frame_rate_tab[frame_rate_code].num;

  640.     h->s.avctx->time_base.num = avpriv_frame_rate_tab[frame_rate_code].den;

  641.     h->s.avctx->width  = s->width;

  642.     h->s.avctx->height = s->height;

  643.     if(!h->top_qp)

  644.         ff_cavs_init_top_lines(h);

  645.     return 0;

  646. }

  647. 

  648. static void cavs_flush(AVCodecContext * avctx) {

  649.     AVSContext *h = avctx->priv_data;

  650.     h->got_keyframe = 0;

  651. }

  652. 

  653. static int cavs_decode_frame(AVCodecContext * avctx,void *data, int *data_size,

  654.                              AVPacket *avpkt) {

  655.     const uint8_t *buf = avpkt->data;

  656.     int buf_size = avpkt->size;

  657.     AVSContext *h = avctx->priv_data;

  658.     MpegEncContext *s = &h->s;

  659.     int input_size;

  660.     const uint8_t *buf_end;

  661.     const uint8_t *buf_ptr;

  662.     AVFrame *picture = data;

  663.     uint32_t stc = -1;

  664. 

  665.     s->avctx = avctx;

  666. 

  667.     if (buf_size == 0) {

  668.         if (!s->low_delay && h->DPB[0].f.data[0]) {

  669.             *data_size = sizeof(AVPicture);

  670.             *picture = h->DPB[0].f;

  671.             memset(&h->DPB[0], 0, sizeof(h->DPB[0]));

  672.         }

  673.         return 0;

  674.     }

  675. 

  676.     buf_ptr = buf;

  677.     buf_end = buf + buf_size;

  678.     for(;;) {

  679.         buf_ptr = avpriv_mpv_find_start_code(buf_ptr,buf_end, &stc);

  680.         if((stc & 0xFFFFFE00) || buf_ptr == buf_end)

  681.             return FFMAX(0, buf_ptr - buf - s->parse_context.last_index);

  682.         input_size = (buf_end - buf_ptr)*8;

  683.         switch(stc) {

  684.         case CAVS_START_CODE:

  685.             init_get_bits(&s->gb, buf_ptr, input_size);

  686.             decode_seq_header(h);

  687.             break;

  688.         case PIC_I_START_CODE:

  689.             if(!h->got_keyframe) {

  690.                 if(h->DPB[0].f.data[0])

  691.                     avctx->release_buffer(avctx, &h->DPB[0].f);

  692.                 if(h->DPB[1].f.data[0])

  693.                     avctx->release_buffer(avctx, &h->DPB[1].f);

  694.                 h->got_keyframe = 1;

  695.             }

  696.         case PIC_PB_START_CODE:

  697.             *data_size = 0;

  698.             if(!h->got_keyframe)

  699.                 break;

  700.             if(!h->top_qp)

  701.                 break;

  702.             init_get_bits(&s->gb, buf_ptr, input_size);

  703.             h->stc = stc;

  704.             if(decode_pic(h))

  705.                 break;

  706.             *data_size = sizeof(AVPicture);

  707.             if(h->pic_type != AV_PICTURE_TYPE_B) {

  708.                 if(h->DPB[1].f.data[0]) {

  709.                     *picture = h->DPB[1].f;

  710.                 } else {

  711.                     *data_size = 0;

  712.                 }

  713.             } else

  714.                 *picture = h->picture.f;

  715.             break;

  716.         case EXT_START_CODE:

  717.             //mpeg_decode_extension(avctx,buf_ptr, input_size);

  718.             break;

  719.         case USER_START_CODE:

  720.             //mpeg_decode_user_data(avctx,buf_ptr, input_size);

  721.             break;

  722.         default:

  723.             if (stc <= SLICE_MAX_START_CODE) {

  724.                 init_get_bits(&s->gb, buf_ptr, input_size);

  725.                 decode_slice_header(h, &s->gb);

  726.             }

  727.             break;

  728.         }

  729.     }

  730. }

  731. 

  732. AVCodec ff_cavs_decoder = {

  733.     .name           = "cavs",

  734.     .type           = AVMEDIA_TYPE_VIDEO,

  735.     .id             = CODEC_ID_CAVS,

  736.     .priv_data_size = sizeof(AVSContext),

  737.     .init           = ff_cavs_init,

  738.     .close          = ff_cavs_end,

  739.     .decode         = cavs_decode_frame,

  740.     .capabilities   = CODEC_CAP_DR1 | CODEC_CAP_DELAY,

  741.     .flush          = cavs_flush,

  742.     .long_name      = NULL_IF_CONFIG_SMALL("Chinese AVS video (AVS1-P2, JiZhun profile)"),

  743. };