split decoder-specific parts into their own file

Originally committed as revision 9533 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 702 insertions, 0 deletions

diff --git a/libavcodec/cavsdec.c b/libavcodec/cavsdec.c
new file mode 100644
index 0000000000..77041e7feb
--- /dev/null
+++ b/libavcodec/cavsdec.c
@@ -0,0 +1,702 @@
+/*
+ * 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 cavs.c
+ * Chinese AVS video (AVS1-P2, JiZhun profile) decoder
+ * @author Stefan Gehrer <stefan.gehrer@gmx.de>
+ */
+
+#include "avcodec.h"
+#include "bitstream.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->mby*h->mb_width + h->mbx)*4 + 0] = h->mv[MV_FWD_X0];
+    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 1] = h->mv[MV_FWD_X1];
+    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 2] = h->mv[MV_FWD_X2];
+    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 3] = h->mv[MV_FWD_X3];
+}
+
+static inline void mv_pred_direct(AVSContext *h, vector_t *pmv_fw,
+                                  vector_t *col_mv) {
+    vector_t *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, vector_t *src, enum block_t size) {
+    vector_t *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 dec_2dvlc_t *r, int esc_golomb_order,
+                                 int qp, uint8_t *dst, int stride) {
+    int i, level_code, esc_code, level, run, mask;
+    DCTELEM level_buf[64];
+    uint8_t run_buf[64];
+    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);
+    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;
+
+    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;
+    }
+    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];
+        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 */
+    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 mb_t mb_type) {
+    GetBitContext *gb = &h->s.gb;
+    int ref[4];
+
+    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 = mb_type;
+}
+
+static void decode_mb_b(AVSContext *h, enum mb_t mb_type) {
+    int block;
+    enum sub_mb_t sub_type[4];
+    int flags;
+
+    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)) {
+            /* 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->mby*h->mb_width+h->mbx)*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)) {
+                    /* 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->mby*h->mb_width + h->mbx)*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;
+    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 void check_for_slice(AVSContext *h) {
+    GetBitContext *gb = &h->s.gb;
+    int align;
+    align = (-get_bits_count(gb)) & 7;
+    if((show_bits_long(gb,24+align) & 0xFFFFFF) == 0x000001) {
+        get_bits_long(gb,24+align);
+        h->stc = get_bits(gb,8);
+        decode_slice_header(h,gb);
+    }
+}
+
+/*****************************************************************************
+ *
+ * frame level
+ *
+ ****************************************************************************/
+
+static int decode_pic(AVSContext *h) {
+    MpegEncContext *s = &h->s;
+    int skip_count;
+    enum mb_t 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);
+    }
+    get_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))
+            get_bits(&s->gb,16);//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);
+    if(h->progressive)
+        h->pic_structure = 1;
+    else if(!(h->pic_structure = get_bits1(&s->gb) && (h->stc == PIC_PB_START_CODE)) )
+        get_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;
+    }
+    check_for_slice(h);
+    if(h->pic_type == FF_I_TYPE) {
+        do {
+            decode_mb_i(h, 0);
+        } while(next_mb(h));
+    } else if(h->pic_type == FF_P_TYPE) {
+        do {
+            if(h->skip_mode_flag) {
+                skip_count = get_ue_golomb(&s->gb);
+                while(skip_count--) {
+                    decode_mb_p(h,P_SKIP);
+                    if(!next_mb(h))
+                        goto done;
+                }
+                mb_type = get_ue_golomb(&s->gb) + P_16X16;
+            } else
+                mb_type = get_ue_golomb(&s->gb) + P_SKIP;
+            if(mb_type > P_8X8) {
+                decode_mb_i(h, mb_type - P_8X8 - 1);
+            } else
+                decode_mb_p(h,mb_type);
+        } while(next_mb(h));
+    } else { /* FF_B_TYPE */
+        do {
+            if(h->skip_mode_flag) {
+                skip_count = get_ue_golomb(&s->gb);
+                while(skip_count--) {
+                    decode_mb_b(h,B_SKIP);
+                    if(!next_mb(h))
+                        goto done;
+                }
+                mb_type = get_ue_golomb(&s->gb) + B_DIRECT;
+            } else
+                mb_type = get_ue_golomb(&s->gb) + B_SKIP;
+            if(mb_type > B_8X8) {
+                decode_mb_i(h, mb_type - B_8X8 - 1);
+            } else
+                decode_mb_b(h,mb_type);
+        } while(next_mb(h));
+    }
+ done:
+    if(h->pic_type != FF_B_TYPE) {
+        if(h->DPB[1].data[0])
+            s->avctx->release_buffer(s->avctx, (AVFrame *)&h->DPB[1]);
+        memcpy(&h->DPB[1], &h->DPB[0], sizeof(Picture));
+        memcpy(&h->DPB[0], &h->picture, sizeof(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,
+                             uint8_t * buf, int buf_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;
+
+    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_MIN_START_CODE &&
+                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,
+};