mpeg12.c

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    }else{
        quant_matrix = s->chroma_intra_matrix;
        component = (n&1) + 1;
    }
    diff = decode_dc(&s->gb, component);
    if (diff >= 0xffff)
        return -1;
    dc = s->last_dc[component];
    dc += diff;
    s->last_dc[component] = dc;
    block[0] = dc << (3 - s->intra_dc_precision);
    if (s->intra_vlc_format)
        rl = &ff_rl_mpeg2;
    else
        rl = &ff_rl_mpeg1;

    {
        OPEN_READER(re, &s->gb);
        /* now quantify & encode AC coefs */
        for(;;) {
            UPDATE_CACHE(re, &s->gb);
            GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);

            if(level == 127){
                break;
            } else if(level != 0) {
                scantable += run;
                j = *scantable;
                level= (level*qscale*quant_matrix[j])>>4;
                level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                LAST_SKIP_BITS(re, &s->gb, 1);
            } else {
                /* escape */
                run = SHOW_UBITS(re, &s->gb, 6)+1; LAST_SKIP_BITS(re, &s->gb, 6);
                UPDATE_CACHE(re, &s->gb);
                level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);
                scantable += run;
                j = *scantable;
                if(level<0){
                    level= (-level*qscale*quant_matrix[j])>>4;
                    level= -level;
                }else{
                    level= (level*qscale*quant_matrix[j])>>4;
                }
            }

            block[j] = level;
        }
        CLOSE_READER(re, &s->gb);
    }

    s->block_last_index[n] = scantable - s->intra_scantable.permutated;
    return 0;
}

typedef struct Mpeg1Context {
    MpegEncContext mpeg_enc_ctx;
    int mpeg_enc_ctx_allocated; /* true if decoding context allocated */
    int repeat_field; /* true if we must repeat the field */
    AVPanScan pan_scan; /** some temporary storage for the panscan */
    int slice_count;
    int swap_uv;//indicate VCR2
    int save_aspect_info;
    int save_width, save_height;
    AVRational frame_rate_ext;       ///< MPEG-2 specific framerate modificator

} Mpeg1Context;

static int mpeg_decode_init(AVCodecContext *avctx)
{
    Mpeg1Context *s = avctx->priv_data;
    MpegEncContext *s2 = &s->mpeg_enc_ctx;
    int i;

    //we need some parmutation to store
    //matrixes, until MPV_common_init()
    //set the real permutatuon
    for(i=0;i<64;i++)
       s2->dsp.idct_permutation[i]=i;

    MPV_decode_defaults(s2);

    s->mpeg_enc_ctx.avctx= avctx;
    s->mpeg_enc_ctx.flags= avctx->flags;
    s->mpeg_enc_ctx.flags2= avctx->flags2;
    ff_mpeg12_common_init(&s->mpeg_enc_ctx);
    init_vlcs();

    s->mpeg_enc_ctx_allocated = 0;
    s->mpeg_enc_ctx.picture_number = 0;
    s->repeat_field = 0;
    s->mpeg_enc_ctx.codec_id= avctx->codec->id;
    return 0;
}

static void quant_matrix_rebuild(uint16_t *matrix, const uint8_t *old_perm,
                                     const uint8_t *new_perm){
    uint16_t temp_matrix[64];
    int i;

    memcpy(temp_matrix,matrix,64*sizeof(uint16_t));

    for(i=0;i<64;i++){
        matrix[new_perm[i]] = temp_matrix[old_perm[i]];
    }
}

//Call this function when we know all parameters
//it may be called in different places for mpeg1 and mpeg2
static int mpeg_decode_postinit(AVCodecContext *avctx){
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    uint8_t old_permutation[64];

    if (
        (s1->mpeg_enc_ctx_allocated == 0)||
        avctx->coded_width  != s->width ||
        avctx->coded_height != s->height||
        s1->save_width != s->width ||
        s1->save_height != s->height ||
        s1->save_aspect_info != s->aspect_ratio_info||
        0)
    {

        if (s1->mpeg_enc_ctx_allocated) {
            ParseContext pc= s->parse_context;
            s->parse_context.buffer=0;
            MPV_common_end(s);
            s->parse_context= pc;
        }

        if( (s->width == 0 )||(s->height == 0))
            return -2;

        avcodec_set_dimensions(avctx, s->width, s->height);
        avctx->bit_rate = s->bit_rate;
        s1->save_aspect_info = s->aspect_ratio_info;
        s1->save_width = s->width;
        s1->save_height = s->height;

     //low_delay may be forced, in this case we will have B frames
     //that behave like P frames
        avctx->has_b_frames = !(s->low_delay);

        if(avctx->sub_id==1){//s->codec_id==avctx->codec_id==CODEC_ID
            //mpeg1 fps
            avctx->time_base.den= ff_frame_rate_tab[s->frame_rate_index].num;
            avctx->time_base.num= ff_frame_rate_tab[s->frame_rate_index].den;
            //mpeg1 aspect
            avctx->sample_aspect_ratio= av_d2q(
                    1.0/ff_mpeg1_aspect[s->aspect_ratio_info], 255);

        }else{//mpeg2
        //mpeg2 fps
            av_reduce(
                &s->avctx->time_base.den,
                &s->avctx->time_base.num,
                ff_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num,
                ff_frame_rate_tab[s->frame_rate_index].den * s1->frame_rate_ext.den,
                1<<30);
        //mpeg2 aspect
            if(s->aspect_ratio_info > 1){
                if( (s1->pan_scan.width == 0 )||(s1->pan_scan.height == 0) ){
                    s->avctx->sample_aspect_ratio=
                        av_div_q(
                         ff_mpeg2_aspect[s->aspect_ratio_info],
                         (AVRational){s->width, s->height}
                         );
                }else{
                    s->avctx->sample_aspect_ratio=
                        av_div_q(
                         ff_mpeg2_aspect[s->aspect_ratio_info],
                         (AVRational){s1->pan_scan.width, s1->pan_scan.height}
                        );
                }
            }else{
                s->avctx->sample_aspect_ratio=
                    ff_mpeg2_aspect[s->aspect_ratio_info];
            }
        }//mpeg2

        if(avctx->xvmc_acceleration){
            avctx->pix_fmt = avctx->get_format(avctx,pixfmt_xvmc_mpg2_420);
        }else{
            if(s->chroma_format <  2){
                avctx->pix_fmt = avctx->get_format(avctx,pixfmt_yuv_420);
            }else
            if(s->chroma_format == 2){
                avctx->pix_fmt = avctx->get_format(avctx,pixfmt_yuv_422);
            }else
            if(s->chroma_format >  2){
                avctx->pix_fmt = avctx->get_format(avctx,pixfmt_yuv_444);
            }
        }
        //until then pix_fmt may be changed right after codec init
        if( avctx->pix_fmt == PIX_FMT_XVMC_MPEG2_IDCT )
            if( avctx->idct_algo == FF_IDCT_AUTO )
                avctx->idct_algo = FF_IDCT_SIMPLE;

        //quantization matrixes may need reordering
        //if dct permutation is changed
        memcpy(old_permutation,s->dsp.idct_permutation,64*sizeof(uint8_t));

        if (MPV_common_init(s) < 0)
            return -2;

        quant_matrix_rebuild(s->intra_matrix,       old_permutation,s->dsp.idct_permutation);
        quant_matrix_rebuild(s->inter_matrix,       old_permutation,s->dsp.idct_permutation);
        quant_matrix_rebuild(s->chroma_intra_matrix,old_permutation,s->dsp.idct_permutation);
        quant_matrix_rebuild(s->chroma_inter_matrix,old_permutation,s->dsp.idct_permutation);

        s1->mpeg_enc_ctx_allocated = 1;
    }
    return 0;
}

static int mpeg1_decode_picture(AVCodecContext *avctx,
                                const uint8_t *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ref, f_code, vbv_delay;

    if(mpeg_decode_postinit(s->avctx) < 0)
       return -2;

    init_get_bits(&s->gb, buf, buf_size*8);

    ref = get_bits(&s->gb, 10); /* temporal ref */
    s->pict_type = get_bits(&s->gb, 3);
    if(s->pict_type == 0 || s->pict_type > 3)
        return -1;

    vbv_delay= get_bits(&s->gb, 16);
    if (s->pict_type == P_TYPE || s->pict_type == B_TYPE) {
        s->full_pel[0] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && avctx->error_resilience >= FF_ER_COMPLIANT)
            return -1;
        s->mpeg_f_code[0][0] = f_code;
        s->mpeg_f_code[0][1] = f_code;
    }
    if (s->pict_type == B_TYPE) {
        s->full_pel[1] = get_bits1(&s->gb);
        f_code = get_bits(&s->gb, 3);
        if (f_code == 0 && avctx->error_resilience >= FF_ER_COMPLIANT)
            return -1;
        s->mpeg_f_code[1][0] = f_code;
        s->mpeg_f_code[1][1] = f_code;
    }
    s->current_picture.pict_type= s->pict_type;
    s->current_picture.key_frame= s->pict_type == I_TYPE;

    if(avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(avctx, AV_LOG_DEBUG, "vbv_delay %d, ref %d type:%d\n", vbv_delay, ref, s->pict_type);

    s->y_dc_scale = 8;
    s->c_dc_scale = 8;
    s->first_slice = 1;
    return 0;
}

static void mpeg_decode_sequence_extension(Mpeg1Context *s1)
{
    MpegEncContext *s= &s1->mpeg_enc_ctx;
    int horiz_size_ext, vert_size_ext;
    int bit_rate_ext;

    skip_bits(&s->gb, 1); /* profil and level esc*/
    s->avctx->profile= get_bits(&s->gb, 3);
    s->avctx->level= get_bits(&s->gb, 4);
    s->progressive_sequence = get_bits1(&s->gb); /* progressive_sequence */
    s->chroma_format = get_bits(&s->gb, 2); /* chroma_format 1=420, 2=422, 3=444 */
    horiz_size_ext = get_bits(&s->gb, 2);
    vert_size_ext = get_bits(&s->gb, 2);
    s->width |= (horiz_size_ext << 12);
    s->height |= (vert_size_ext << 12);
    bit_rate_ext = get_bits(&s->gb, 12);  /* XXX: handle it */
    s->bit_rate += (bit_rate_ext << 18) * 400;
    skip_bits1(&s->gb); /* marker */
    s->avctx->rc_buffer_size += get_bits(&s->gb, 8)*1024*16<<10;

    s->low_delay = get_bits1(&s->gb);
    if(s->flags & CODEC_FLAG_LOW_DELAY) s->low_delay=1;

    s1->frame_rate_ext.num = get_bits(&s->gb, 2)+1;
    s1->frame_rate_ext.den = get_bits(&s->gb, 5)+1;

    dprintf(s->avctx, "sequence extension\n");
    s->codec_id= s->avctx->codec_id= CODEC_ID_MPEG2VIDEO;
    s->avctx->sub_id = 2; /* indicates mpeg2 found */

    if(s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "profile: %d, level: %d vbv buffer: %d, bitrate:%d\n",
               s->avctx->profile, s->avctx->level, s->avctx->rc_buffer_size, s->bit_rate);

}

static void mpeg_decode_sequence_display_extension(Mpeg1Context *s1)
{
    MpegEncContext *s= &s1->mpeg_enc_ctx;
    int color_description, w, h;

    skip_bits(&s->gb, 3); /* video format */
    color_description= get_bits1(&s->gb);
    if(color_description){
        skip_bits(&s->gb, 8); /* color primaries */
        skip_bits(&s->gb, 8); /* transfer_characteristics */
        skip_bits(&s->gb, 8); /* matrix_coefficients */
    }
    w= get_bits(&s->gb, 14);
    skip_bits(&s->gb, 1); //marker
    h= get_bits(&s->gb, 14);
    skip_bits(&s->gb, 1); //marker

    s1->pan_scan.width= 16*w;
    s1->pan_scan.height=16*h;

    if(s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "sde w:%d, h:%d\n", w, h);
}

static void mpeg_decode_picture_display_extension(Mpeg1Context *s1)
{
    MpegEncContext *s= &s1->mpeg_enc_ctx;
    int i,nofco;

    nofco = 1;
    if(s->progressive_sequence){
        if(s->repeat_first_field){
            nofco++;
            if(s->top_field_first)
                nofco++;
        }
    }else{
        if(s->picture_structure == PICT_FRAME){
            nofco++;
            if(s->repeat_first_field)
                nofco++;
        }
    }
    for(i=0; i<nofco; i++){
        s1->pan_scan.position[i][0]= get_sbits(&s->gb, 16);
        skip_bits(&s->gb, 1); //marker
        s1->pan_scan.position[i][1]= get_sbits(&s->gb, 16);
        skip_bits(&s->gb, 1); //marker
    }

    if(s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "pde (%d,%d) (%d,%d) (%d,%d)\n",
            s1->pan_scan.position[0][0], s1->pan_scan.position[0][1],
            s1->pan_scan.position[1][0], s1->pan_scan.position[1][1],
            s1->pan_scan.position[2][0], s1->pan_scan.position[2][1]
        );
}

static void mpeg_decode_quant_matrix_extension(MpegEncContext *s)
{
    int i, v, j;

    dprintf(s->avctx, "matrix extension\n");

    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->intra_matrix[j] = v;
            s->chroma_intra_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {
            v = get_bits(&s->gb, 8);
            j= s->dsp.idct_permutation[ ff_zigzag_direct[i] ];
            s->inter_matrix[j] = v;
            s->chroma_inter_matrix[j] = v;
        }
    }
    if (get_bits1(&s->gb)) {
        for(i=0;i<64;i++) {