PeerStreamer

/*

 * 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 libavcodec/cavsdec.c

 * 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, level_code, esc_code, level, run, mask;

    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;

            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->s.dsp.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 > 63){

        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;

    int block, pred_mode_uv;

    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 == FF_I_TYPE)

        cbp_code = get_ue_golomb(gb);

    if(cbp_code > 63){

        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 != FF_I_TYPE) || (!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))

        get_bits(gb,8);

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

        skip_bits_long(gb,24+align);

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

        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) + FF_I_TYPE;

        if(h->pic_type > FF_B_TYPE) {

            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 == FF_B_TYPE))

            return -1;

    } else {

        h->pic_type = FF_I_TYPE;

        if(get_bits1(&s->gb))

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

    }

    /* 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 != FF_B_TYPE) {

        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 == FF_B_TYPE) {

        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 == FF_I_TYPE) {

        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 == FF_B_TYPE && 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 == FF_I_TYPE) {

        do {

            check_for_slice(h);

            decode_mb_i(h, 0);

        } while(ff_cavs_next_mb(h));

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

        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 { /* FF_B_TYPE */

        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 != FF_B_TYPE) {

        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)

            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 != FF_B_TYPE) {

                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 cavs_decoder = {

    "cavs",

    CODEC_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)"),

};