/*
  * Chinese AVS video (AVS1-P2, JiZhun profile) decoder.
  * Copyright (c) 2006  Stefan Gehrer <stefan.gehrer@gmx.de>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * @file

  * Chinese AVS video (AVS1-P2, JiZhun profile) decoder
  * @author Stefan Gehrer <stefan.gehrer@gmx.de>
  */
 
 #include "avcodec.h"

 #include "get_bits.h"

 #include "golomb.h"
 #include "cavs.h"
 
 static const uint8_t mv_scan[4] = {
     MV_FWD_X0,MV_FWD_X1,
     MV_FWD_X2,MV_FWD_X3
 };
 
 static const uint8_t cbp_tab[64][2] = {
   {63, 0},{15,15},{31,63},{47,31},{ 0,16},{14,32},{13,47},{11,13},
   { 7,14},{ 5,11},{10,12},{ 8, 5},{12,10},{61, 7},{ 4,48},{55, 3},
   { 1, 2},{ 2, 8},{59, 4},{ 3, 1},{62,61},{ 9,55},{ 6,59},{29,62},
   {45,29},{51,27},{23,23},{39,19},{27,30},{46,28},{53, 9},{30, 6},
   {43,60},{37,21},{60,44},{16,26},{21,51},{28,35},{19,18},{35,20},
   {42,24},{26,53},{44,17},{32,37},{58,39},{24,45},{20,58},{17,43},
   {18,42},{48,46},{22,36},{33,33},{25,34},{49,40},{40,52},{36,49},
   {34,50},{50,56},{52,25},{54,22},{41,54},{56,57},{38,41},{57,38}
 };
 
 /*****************************************************************************
  *
  * motion vector prediction
  *
  ****************************************************************************/
 
 static inline void store_mvs(AVSContext *h) {

     h->col_mv[h->mbidx*4 + 0] = h->mv[MV_FWD_X0];
     h->col_mv[h->mbidx*4 + 1] = h->mv[MV_FWD_X1];
     h->col_mv[h->mbidx*4 + 2] = h->mv[MV_FWD_X2];
     h->col_mv[h->mbidx*4 + 3] = h->mv[MV_FWD_X3];

 }
 

 static inline void mv_pred_direct(AVSContext *h, cavs_vector *pmv_fw,
                                   cavs_vector *col_mv) {
     cavs_vector *pmv_bw = pmv_fw + MV_BWD_OFFS;

     int den = h->direct_den[col_mv->ref];
     int m = col_mv->x >> 31;
 
     pmv_fw->dist = h->dist[1];
     pmv_bw->dist = h->dist[0];
     pmv_fw->ref = 1;
     pmv_bw->ref = 0;
     /* scale the co-located motion vector according to its temporal span */
     pmv_fw->x = (((den+(den*col_mv->x*pmv_fw->dist^m)-m-1)>>14)^m)-m;
     pmv_bw->x = m-(((den+(den*col_mv->x*pmv_bw->dist^m)-m-1)>>14)^m);
     m = col_mv->y >> 31;
     pmv_fw->y = (((den+(den*col_mv->y*pmv_fw->dist^m)-m-1)>>14)^m)-m;
     pmv_bw->y = m-(((den+(den*col_mv->y*pmv_bw->dist^m)-m-1)>>14)^m);
 }
 

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

     cavs_vector *dst = src + MV_BWD_OFFS;

 
     /* backward mv is the scaled and negated forward mv */
     dst->x = -((src->x * h->sym_factor + 256) >> 9);
     dst->y = -((src->y * h->sym_factor + 256) >> 9);
     dst->ref = 0;
     dst->dist = h->dist[0];
     set_mvs(dst, size);
 }
 
 /*****************************************************************************
  *
  * residual data decoding
  *
  ****************************************************************************/
 
 /** kth-order exponential golomb code */
 static inline int get_ue_code(GetBitContext *gb, int order) {
     if(order) {
         int ret = get_ue_golomb(gb) << order;
         return ret + get_bits(gb,order);
     }
     return get_ue_golomb(gb);
 }
 
 /**
  * decode coefficients from one 8x8 block, dequantize, inverse transform
  *  and add them to sample block
  * @param r pointer to 2D VLC table
  * @param esc_golomb_order escape codes are k-golomb with this order k
  * @param qp quantizer
  * @param dst location of sample block
  * @param stride line stride in frame buffer
  */
 static int decode_residual_block(AVSContext *h, GetBitContext *gb,

                                  const struct dec_2dvlc *r, int esc_golomb_order,

                                  int qp, uint8_t *dst, int stride) {

     int i, esc_code, level, mask;
     unsigned int level_code, run;

     DCTELEM level_buf[65];
     uint8_t run_buf[65];

     DCTELEM *block = h->block;
 
     for(i=0;i<65;i++) {
         level_code = get_ue_code(gb,r->golomb_order);
         if(level_code >= ESCAPE_CODE) {
             run = ((level_code - ESCAPE_CODE) >> 1) + 1;

             if(run > 64)
                 return -1;

             esc_code = get_ue_code(gb,esc_golomb_order);
             level = esc_code + (run > r->max_run ? 1 : r->level_add[run]);
             while(level > r->inc_limit)
                 r++;
             mask = -(level_code & 1);
             level = (level^mask) - mask;
         } else {
             level = r->rltab[level_code][0];
             if(!level) //end of block signal
                 break;
             run   = r->rltab[level_code][1];
             r += r->rltab[level_code][2];
         }
         level_buf[i] = level;
         run_buf[i] = run;
     }
     if(dequant(h,level_buf, run_buf, block, ff_cavs_dequant_mul[qp],
                ff_cavs_dequant_shift[qp], i))
         return -1;

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

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

     return 0;
 }
 
 
 static inline void decode_residual_chroma(AVSContext *h) {
     if(h->cbp & (1<<4))
         decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,
                               ff_cavs_chroma_qp[h->qp],h->cu,h->c_stride);
     if(h->cbp & (1<<5))
         decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,
                               ff_cavs_chroma_qp[h->qp],h->cv,h->c_stride);
 }
 
 static inline int decode_residual_inter(AVSContext *h) {
     int block;
 
     /* get coded block pattern */
     int cbp= get_ue_golomb(&h->s.gb);

     if(cbp > 63U){

         av_log(h->s.avctx, AV_LOG_ERROR, "illegal inter cbp\n");
         return -1;
     }
     h->cbp = cbp_tab[cbp][1];
 
     /* get quantizer */
     if(h->cbp && !h->qp_fixed)
         h->qp = (h->qp + get_se_golomb(&h->s.gb)) & 63;
     for(block=0;block<4;block++)
         if(h->cbp & (1<<block))
             decode_residual_block(h,&h->s.gb,ff_cavs_inter_dec,0,h->qp,
                                   h->cy + h->luma_scan[block], h->l_stride);
     decode_residual_chroma(h);
 
     return 0;
 }
 
 /*****************************************************************************
  *
  * macroblock level
  *
  ****************************************************************************/
 
 static int decode_mb_i(AVSContext *h, int cbp_code) {
     GetBitContext *gb = &h->s.gb;

     unsigned pred_mode_uv;
     int block;

     uint8_t top[18];
     uint8_t *left = NULL;
     uint8_t *d;
 

     ff_cavs_init_mb(h);

 
     /* get intra prediction modes from stream */
     for(block=0;block<4;block++) {
         int nA,nB,predpred;
         int pos = ff_cavs_scan3x3[block];
 
         nA = h->pred_mode_Y[pos-1];
         nB = h->pred_mode_Y[pos-3];
         predpred = FFMIN(nA,nB);
         if(predpred == NOT_AVAIL) // if either is not available
             predpred = INTRA_L_LP;
         if(!get_bits1(gb)){
             int rem_mode= get_bits(gb, 2);
             predpred = rem_mode + (rem_mode >= predpred);
         }
         h->pred_mode_Y[pos] = predpred;
     }
     pred_mode_uv = get_ue_golomb(gb);
     if(pred_mode_uv > 6) {
         av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra chroma pred mode\n");
         return -1;
     }

     ff_cavs_modify_mb_i(h, &pred_mode_uv);

 
     /* get coded block pattern */

     if(h->pic_type == AV_PICTURE_TYPE_I)

         cbp_code = get_ue_golomb(gb);

     if(cbp_code > 63U){

         av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra cbp\n");
         return -1;
     }
     h->cbp = cbp_tab[cbp_code][0];
     if(h->cbp && !h->qp_fixed)
         h->qp = (h->qp + get_se_golomb(gb)) & 63; //qp_delta
 
     /* luma intra prediction interleaved with residual decode/transform/add */
     for(block=0;block<4;block++) {
         d = h->cy + h->luma_scan[block];

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

         h->intra_pred_l[h->pred_mode_Y[ff_cavs_scan3x3[block]]]
             (d, top, left, h->l_stride);
         if(h->cbp & (1<<block))
             decode_residual_block(h,gb,ff_cavs_intra_dec,1,h->qp,d,h->l_stride);
     }
 
     /* chroma intra prediction */

     ff_cavs_load_intra_pred_chroma(h);

     h->intra_pred_c[pred_mode_uv](h->cu, &h->top_border_u[h->mbx*10],
                                   h->left_border_u, h->c_stride);
     h->intra_pred_c[pred_mode_uv](h->cv, &h->top_border_v[h->mbx*10],
                                   h->left_border_v, h->c_stride);
 
     decode_residual_chroma(h);
     ff_cavs_filter(h,I_8X8);
     set_mv_intra(h);
     return 0;
 }
 

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

     GetBitContext *gb = &h->s.gb;
     int ref[4];
 

     ff_cavs_init_mb(h);

     switch(mb_type) {
     case P_SKIP:
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_PSKIP,  BLK_16X16, 0);
         break;
     case P_16X16:
         ref[0] = h->ref_flag ? 0 : get_bits1(gb);
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16,ref[0]);
         break;
     case P_16X8:
         ref[0] = h->ref_flag ? 0 : get_bits1(gb);
         ref[2] = h->ref_flag ? 0 : get_bits1(gb);
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,    BLK_16X8, ref[0]);
         ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT,   BLK_16X8, ref[2]);
         break;
     case P_8X16:
         ref[0] = h->ref_flag ? 0 : get_bits1(gb);
         ref[1] = h->ref_flag ? 0 : get_bits1(gb);
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT,   BLK_8X16, ref[0]);
         ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_TOPRIGHT,BLK_8X16, ref[1]);
         break;
     case P_8X8:
         ref[0] = h->ref_flag ? 0 : get_bits1(gb);
         ref[1] = h->ref_flag ? 0 : get_bits1(gb);
         ref[2] = h->ref_flag ? 0 : get_bits1(gb);
         ref[3] = h->ref_flag ? 0 : get_bits1(gb);
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_MEDIAN,   BLK_8X8, ref[0]);
         ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_MEDIAN,   BLK_8X8, ref[1]);
         ff_cavs_mv(h, MV_FWD_X2, MV_FWD_X1, MV_PRED_MEDIAN,   BLK_8X8, ref[2]);
         ff_cavs_mv(h, MV_FWD_X3, MV_FWD_X0, MV_PRED_MEDIAN,   BLK_8X8, ref[3]);
     }
     ff_cavs_inter(h, mb_type);
     set_intra_mode_default(h);
     store_mvs(h);
     if(mb_type != P_SKIP)
         decode_residual_inter(h);
     ff_cavs_filter(h,mb_type);

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

 }
 

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

     int block;

     enum cavs_sub_mb sub_type[4];

     int flags;
 

     ff_cavs_init_mb(h);

 
     /* reset all MVs */
     h->mv[MV_FWD_X0] = ff_cavs_dir_mv;
     set_mvs(&h->mv[MV_FWD_X0], BLK_16X16);
     h->mv[MV_BWD_X0] = ff_cavs_dir_mv;
     set_mvs(&h->mv[MV_BWD_X0], BLK_16X16);
     switch(mb_type) {
     case B_SKIP:
     case B_DIRECT:

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

             /* intra MB at co-location, do in-plane prediction */
             ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_BSKIP, BLK_16X16, 1);
             ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_BSKIP, BLK_16X16, 0);
         } else
             /* direct prediction from co-located P MB, block-wise */
             for(block=0;block<4;block++)
                 mv_pred_direct(h,&h->mv[mv_scan[block]],

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

         break;
     case B_FWD_16X16:
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);
         break;
     case B_SYM_16X16:
         ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);
         mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X16);
         break;
     case B_BWD_16X16:
         ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_MEDIAN, BLK_16X16, 0);
         break;
     case B_8X8:
         for(block=0;block<4;block++)
             sub_type[block] = get_bits(&h->s.gb,2);
         for(block=0;block<4;block++) {
             switch(sub_type[block]) {
             case B_SUB_DIRECT:

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

                     /* intra MB at co-location, do in-plane prediction */
                     ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                             MV_PRED_BSKIP, BLK_8X8, 1);
                     ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,
                             mv_scan[block]-3+MV_BWD_OFFS,
                             MV_PRED_BSKIP, BLK_8X8, 0);
                 } else
                     mv_pred_direct(h,&h->mv[mv_scan[block]],

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

                 break;
             case B_SUB_FWD:
                 ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                         MV_PRED_MEDIAN, BLK_8X8, 1);
                 break;
             case B_SUB_SYM:
                 ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                         MV_PRED_MEDIAN, BLK_8X8, 1);
                 mv_pred_sym(h, &h->mv[mv_scan[block]], BLK_8X8);
                 break;
             }
         }
         for(block=0;block<4;block++) {
             if(sub_type[block] == B_SUB_BWD)
                 ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,
                         mv_scan[block]+MV_BWD_OFFS-3,
                         MV_PRED_MEDIAN, BLK_8X8, 0);
         }
         break;
     default:
         assert((mb_type > B_SYM_16X16) && (mb_type < B_8X8));
         flags = ff_cavs_partition_flags[mb_type];
         if(mb_type & 1) { /* 16x8 macroblock types */
             if(flags & FWD0)
                 ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,  BLK_16X8, 1);
             if(flags & SYM0)
                 mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X8);
             if(flags & FWD1)
                 ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT, BLK_16X8, 1);
             if(flags & SYM1)
                 mv_pred_sym(h, &h->mv[MV_FWD_X2], BLK_16X8);
             if(flags & BWD0)
                 ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_TOP,  BLK_16X8, 0);
             if(flags & BWD1)
                 ff_cavs_mv(h, MV_BWD_X2, MV_BWD_A1, MV_PRED_LEFT, BLK_16X8, 0);
         } else {          /* 8x16 macroblock types */
             if(flags & FWD0)
                 ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT, BLK_8X16, 1);
             if(flags & SYM0)
                 mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_8X16);
             if(flags & FWD1)
                 ff_cavs_mv(h,MV_FWD_X1,MV_FWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,1);
             if(flags & SYM1)
                 mv_pred_sym(h, &h->mv[MV_FWD_X1], BLK_8X16);
             if(flags & BWD0)
                 ff_cavs_mv(h, MV_BWD_X0, MV_BWD_B3, MV_PRED_LEFT, BLK_8X16, 0);
             if(flags & BWD1)
                 ff_cavs_mv(h,MV_BWD_X1,MV_BWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,0);
         }
     }
     ff_cavs_inter(h, mb_type);
     set_intra_mode_default(h);
     if(mb_type != B_SKIP)
         decode_residual_inter(h);
     ff_cavs_filter(h,mb_type);
 }
 
 /*****************************************************************************
  *
  * slice level
  *
  ****************************************************************************/
 
 static inline int decode_slice_header(AVSContext *h, GetBitContext *gb) {
     if(h->stc > 0xAF)
         av_log(h->s.avctx, AV_LOG_ERROR, "unexpected start code 0x%02x\n", h->stc);
     h->mby = h->stc;

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

 
     /* mark top macroblocks as unavailable */
     h->flags &= ~(B_AVAIL|C_AVAIL);

     if((h->mby == 0) && (!h->qp_fixed)){
         h->qp_fixed = get_bits1(gb);
         h->qp = get_bits(gb,6);
     }
     /* inter frame or second slice can have weighting params */

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

         if(get_bits1(gb)) { //slice_weighting_flag
             av_log(h->s.avctx, AV_LOG_ERROR,
                    "weighted prediction not yet supported\n");
         }
     return 0;
 }
 

 static inline int check_for_slice(AVSContext *h) {

     GetBitContext *gb = &h->s.gb;
     int align;

 
     if(h->mbx)

         return 0;

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

     /* check for stuffing byte */
     if(!align && (show_bits(gb,8) == 0x80))

         align = 8;

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

         skip_bits_long(gb,24+align);

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

         if (h->stc >= h->mb_height)
             return 0;

         decode_slice_header(h,gb);

         return 1;

     }

     return 0;

 }
 
 /*****************************************************************************
  *
  * frame level
  *
  ****************************************************************************/
 
 static int decode_pic(AVSContext *h) {
     MpegEncContext *s = &h->s;

     int skip_count = -1;

     enum cavs_mb mb_type;

 
     if (!s->context_initialized) {
         s->avctx->idct_algo = FF_IDCT_CAVS;
         if (MPV_common_init(s) < 0)
             return -1;
         ff_init_scantable(s->dsp.idct_permutation,&h->scantable,ff_zigzag_direct);
     }

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

     if(h->stc == PIC_PB_START_CODE) {

         h->pic_type = get_bits(&s->gb,2) + AV_PICTURE_TYPE_I;
         if(h->pic_type > AV_PICTURE_TYPE_B) {

             av_log(s->avctx, AV_LOG_ERROR, "illegal picture type\n");
             return -1;
         }
         /* make sure we have the reference frames we need */
         if(!h->DPB[0].data[0] ||

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

             return -1;
     } else {

         h->pic_type = AV_PICTURE_TYPE_I;

         if(get_bits1(&s->gb))

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

         /* old sample clips were all progressive and no low_delay,
            bump stream revision if detected otherwise */
         if((s->low_delay) || !(show_bits(&s->gb,9) & 1))
             h->stream_revision = 1;
         /* similarly test top_field_first and repeat_first_field */
         else if(show_bits(&s->gb,11) & 3)
             h->stream_revision = 1;
         if(h->stream_revision > 0)
             skip_bits(&s->gb,1); //marker_bit

     }
     /* release last B frame */
     if(h->picture.data[0])
         s->avctx->release_buffer(s->avctx, (AVFrame *)&h->picture);
 
     s->avctx->get_buffer(s->avctx, (AVFrame *)&h->picture);
     ff_cavs_init_pic(h);
     h->picture.poc = get_bits(&s->gb,8)*2;
 
     /* get temporal distances and MV scaling factors */

     if(h->pic_type != AV_PICTURE_TYPE_B) {

         h->dist[0] = (h->picture.poc - h->DPB[0].poc  + 512) % 512;
     } else {
         h->dist[0] = (h->DPB[0].poc  - h->picture.poc + 512) % 512;
     }
     h->dist[1] = (h->picture.poc - h->DPB[1].poc  + 512) % 512;
     h->scale_den[0] = h->dist[0] ? 512/h->dist[0] : 0;
     h->scale_den[1] = h->dist[1] ? 512/h->dist[1] : 0;

     if(h->pic_type == AV_PICTURE_TYPE_B) {

         h->sym_factor = h->dist[0]*h->scale_den[1];
     } else {
         h->direct_den[0] = h->dist[0] ? 16384/h->dist[0] : 0;
         h->direct_den[1] = h->dist[1] ? 16384/h->dist[1] : 0;
     }
 
     if(s->low_delay)
         get_ue_golomb(&s->gb); //bbv_check_times
     h->progressive             = get_bits1(&s->gb);

     h->pic_structure = 1;
     if(!h->progressive)
         h->pic_structure = get_bits1(&s->gb);
     if(!h->pic_structure && h->stc == PIC_PB_START_CODE)

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

     skip_bits1(&s->gb);        //top_field_first
     skip_bits1(&s->gb);        //repeat_first_field
     h->qp_fixed                = get_bits1(&s->gb);
     h->qp                      = get_bits(&s->gb,6);

     if(h->pic_type == AV_PICTURE_TYPE_I) {

         if(!h->progressive && !h->pic_structure)
             skip_bits1(&s->gb);//what is this?
         skip_bits(&s->gb,4);   //reserved bits
     } else {

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

             h->ref_flag        = get_bits1(&s->gb);
         skip_bits(&s->gb,4);   //reserved bits
         h->skip_mode_flag      = get_bits1(&s->gb);
     }
     h->loop_filter_disable     = get_bits1(&s->gb);
     if(!h->loop_filter_disable && get_bits1(&s->gb)) {
         h->alpha_offset        = get_se_golomb(&s->gb);
         h->beta_offset         = get_se_golomb(&s->gb);
     } else {
         h->alpha_offset = h->beta_offset  = 0;
     }

     if(h->pic_type == AV_PICTURE_TYPE_I) {

         do {

             check_for_slice(h);

             decode_mb_i(h, 0);

         } while(ff_cavs_next_mb(h));

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

         do {

             if(check_for_slice(h))
                 skip_count = -1;
             if(h->skip_mode_flag && (skip_count < 0))

                 skip_count = get_ue_golomb(&s->gb);

             if(h->skip_mode_flag && skip_count--) {
                 decode_mb_p(h,P_SKIP);
             } else {
                 mb_type = get_ue_golomb(&s->gb) + P_SKIP + h->skip_mode_flag;
                 if(mb_type > P_8X8)
                     decode_mb_i(h, mb_type - P_8X8 - 1);
                 else
                     decode_mb_p(h,mb_type);
             }

         } while(ff_cavs_next_mb(h));

     } else { /* AV_PICTURE_TYPE_B */

         do {

             if(check_for_slice(h))
                 skip_count = -1;
             if(h->skip_mode_flag && (skip_count < 0))

                 skip_count = get_ue_golomb(&s->gb);

             if(h->skip_mode_flag && skip_count--) {
                 decode_mb_b(h,B_SKIP);
             } else {
                 mb_type = get_ue_golomb(&s->gb) + B_SKIP + h->skip_mode_flag;
                 if(mb_type > B_8X8)
                     decode_mb_i(h, mb_type - B_8X8 - 1);
                 else
                     decode_mb_b(h,mb_type);
             }

         } while(ff_cavs_next_mb(h));

     }

     if(h->pic_type != AV_PICTURE_TYPE_B) {

         if(h->DPB[1].data[0])
             s->avctx->release_buffer(s->avctx, (AVFrame *)&h->DPB[1]);

         h->DPB[1] = h->DPB[0];
         h->DPB[0] = h->picture;

         memset(&h->picture,0,sizeof(Picture));
     }
     return 0;
 }
 
 /*****************************************************************************
  *
  * headers and interface
  *
  ****************************************************************************/
 
 static int decode_seq_header(AVSContext *h) {
     MpegEncContext *s = &h->s;
     int frame_rate_code;
 
     h->profile =         get_bits(&s->gb,8);
     h->level =           get_bits(&s->gb,8);
     skip_bits1(&s->gb); //progressive sequence
     s->width =           get_bits(&s->gb,14);
     s->height =          get_bits(&s->gb,14);
     skip_bits(&s->gb,2); //chroma format
     skip_bits(&s->gb,3); //sample_precision
     h->aspect_ratio =    get_bits(&s->gb,4);
     frame_rate_code =    get_bits(&s->gb,4);
     skip_bits(&s->gb,18);//bit_rate_lower
     skip_bits1(&s->gb);  //marker_bit
     skip_bits(&s->gb,12);//bit_rate_upper
     s->low_delay =       get_bits1(&s->gb);
     h->mb_width  = (s->width  + 15) >> 4;
     h->mb_height = (s->height + 15) >> 4;
     h->s.avctx->time_base.den = ff_frame_rate_tab[frame_rate_code].num;
     h->s.avctx->time_base.num = ff_frame_rate_tab[frame_rate_code].den;
     h->s.avctx->width  = s->width;
     h->s.avctx->height = s->height;
     if(!h->top_qp)
         ff_cavs_init_top_lines(h);
     return 0;
 }
 
 static void cavs_flush(AVCodecContext * avctx) {
     AVSContext *h = avctx->priv_data;
     h->got_keyframe = 0;
 }
 
 static int cavs_decode_frame(AVCodecContext * avctx,void *data, int *data_size,

                              AVPacket *avpkt) {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;

     AVSContext *h = avctx->priv_data;
     MpegEncContext *s = &h->s;
     int input_size;
     const uint8_t *buf_end;
     const uint8_t *buf_ptr;
     AVFrame *picture = data;

     uint32_t stc = -1;

 
     s->avctx = avctx;
 
     if (buf_size == 0) {
         if(!s->low_delay && h->DPB[0].data[0]) {
             *data_size = sizeof(AVPicture);
             *picture = *(AVFrame *) &h->DPB[0];
         }
         return 0;
     }
 
     buf_ptr = buf;
     buf_end = buf + buf_size;
     for(;;) {
         buf_ptr = ff_find_start_code(buf_ptr,buf_end, &stc);

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

             return FFMAX(0, buf_ptr - buf - s->parse_context.last_index);
         input_size = (buf_end - buf_ptr)*8;
         switch(stc) {
         case CAVS_START_CODE:
             init_get_bits(&s->gb, buf_ptr, input_size);
             decode_seq_header(h);
             break;
         case PIC_I_START_CODE:
             if(!h->got_keyframe) {
                 if(h->DPB[0].data[0])
                     avctx->release_buffer(avctx, (AVFrame *)&h->DPB[0]);
                 if(h->DPB[1].data[0])
                     avctx->release_buffer(avctx, (AVFrame *)&h->DPB[1]);
                 h->got_keyframe = 1;
             }
         case PIC_PB_START_CODE:
             *data_size = 0;
             if(!h->got_keyframe)
                 break;
             init_get_bits(&s->gb, buf_ptr, input_size);
             h->stc = stc;
             if(decode_pic(h))
                 break;
             *data_size = sizeof(AVPicture);

             if(h->pic_type != AV_PICTURE_TYPE_B) {

                 if(h->DPB[1].data[0]) {
                     *picture = *(AVFrame *) &h->DPB[1];
                 } else {
                     *data_size = 0;
                 }
             } else
                 *picture = *(AVFrame *) &h->picture;
             break;
         case EXT_START_CODE:
             //mpeg_decode_extension(avctx,buf_ptr, input_size);
             break;
         case USER_START_CODE:
             //mpeg_decode_user_data(avctx,buf_ptr, input_size);
             break;
         default:

             if (stc <= SLICE_MAX_START_CODE) {

                 init_get_bits(&s->gb, buf_ptr, input_size);
                 decode_slice_header(h, &s->gb);
             }
             break;
         }
     }
 }
 

 AVCodec ff_cavs_decoder = {

     "cavs",

     AVMEDIA_TYPE_VIDEO,

     CODEC_ID_CAVS,
     sizeof(AVSContext),
     ff_cavs_init,
     NULL,
     ff_cavs_end,
     cavs_decode_frame,
     CODEC_CAP_DR1 | CODEC_CAP_DELAY,
     .flush= cavs_flush,

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

 };