mpeg12.c

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        else
            quant_matrix = s->chroma_inter_matrix;

        /* special case for the first coef. no need to add a second vlc table */
        UPDATE_CACHE(re, &s->gb);
        v= SHOW_UBITS(re, &s->gb, 2);
        if (v & 2) {
            LAST_SKIP_BITS(re, &s->gb, 2);
            level= (3*qscale*quant_matrix[0])>>5;
            if(v&1)
                level= -level;
            block[0] = level;
            mismatch ^= level;
            i++;
        }

        /* 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);
            
            if(level == 127){
                break;
            } else if(level != 0) {
                i += run;
                j = scantable[i];
                level= ((level*2+1)*qscale*quant_matrix[j])>>5;
                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);

                i += run;
                j = scantable[i];
                if(level<0){
                    level= ((-level*2+1)*qscale*quant_matrix[j])>>5;
                    level= -level;
                }else{
                    level= ((level*2+1)*qscale*quant_matrix[j])>>5;
                }
            }
            if (i > 63){
                fprintf(stderr, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
            
            mismatch ^= level;
            block[j] = level;
        }
        CLOSE_READER(re, &s->gb);
    }
    block[63] ^= (mismatch & 1);
    
    s->block_last_index[n] = i;
    return 0;
}

static inline int mpeg2_decode_block_intra(MpegEncContext *s, 
                               DCTELEM *block, 
                               int n)
{
    int level, dc, diff, i, j, run;
    int component;
    RLTable *rl;
    UINT8 * const scantable= s->intra_scantable.permutated;
    const UINT16 *quant_matrix;
    const int qscale= s->qscale;
    int mismatch;

    /* DC coef */
    if (n < 4){
        quant_matrix = s->intra_matrix;
        component = 0; 
    }else{
        quant_matrix = s->chroma_intra_matrix;
        component = n - 3;
    }
    diff = decode_dc(s, 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);
    dprintf("dc=%d\n", block[0]);
    mismatch = block[0] ^ 1;
    i = 0;
    if (s->intra_vlc_format)
        rl = &rl_mpeg2;
    else
        rl = &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);
            
            if(level == 127){
                break;
            } else if(level != 0) {
                i += run;
                j = scantable[i];
                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);
                i += run;
                j = scantable[i];
                if(level<0){
                    level= (-level*qscale*quant_matrix[j])>>4;
                    level= -level;
                }else{
                    level= (level*qscale*quant_matrix[j])>>4;
                }
            }
            if (i > 63){
                fprintf(stderr, "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
            
            mismatch^= level;
            block[j] = level;
        }
        CLOSE_READER(re, &s->gb);
    }
    block[63]^= mismatch&1;
    
    s->block_last_index[n] = i;
    return 0;
}

/* compressed picture size */
#define PICTURE_BUFFER_SIZE 100000

typedef struct Mpeg1Context {
    MpegEncContext mpeg_enc_ctx;
    UINT32 header_state;
    int start_code; /* current start code */
    UINT8 buffer[PICTURE_BUFFER_SIZE]; 
    UINT8 *buf_ptr;
    int buffer_size;
    int mpeg_enc_ctx_allocated; /* true if decoding context allocated */
    int repeat_field; /* true if we must repeat the field */
} Mpeg1Context;

static int mpeg_decode_init(AVCodecContext *avctx)
{
    Mpeg1Context *s = avctx->priv_data;
    
    s->mpeg_enc_ctx.flags= avctx->flags;
    common_init(&s->mpeg_enc_ctx);
    init_vlcs(&s->mpeg_enc_ctx);

    s->header_state = 0xff;
    s->mpeg_enc_ctx_allocated = 0;
    s->buffer_size = PICTURE_BUFFER_SIZE;
    s->start_code = -1;
    s->buf_ptr = s->buffer;
    s->mpeg_enc_ctx.picture_number = 0;
    s->repeat_field = 0;
    s->mpeg_enc_ctx.codec_id= avctx->codec->id;
    avctx->mbskip_table= s->mpeg_enc_ctx.mbskip_table;
    return 0;
}

/* return the 8 bit start code value and update the search
   state. Return -1 if no start code found */
static int find_start_code(UINT8 **pbuf_ptr, UINT8 *buf_end, 
                           UINT32 *header_state)
{
    UINT8 *buf_ptr;
    unsigned int state, v;
    int val;

    state = *header_state;
    buf_ptr = *pbuf_ptr;
    while (buf_ptr < buf_end) {
        v = *buf_ptr++;
        if (state == 0x000001) {
            state = ((state << 8) | v) & 0xffffff;
            val = state;
            goto found;
        }
        state = ((state << 8) | v) & 0xffffff;
    }
    val = -1;
 found:
    *pbuf_ptr = buf_ptr;
    *header_state = state;
    return val;
}

static int mpeg1_decode_picture(AVCodecContext *avctx, 
                                UINT8 *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ref, f_code;

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

    ref = get_bits(&s->gb, 10); /* temporal ref */
    s->pict_type = get_bits(&s->gb, 3);
    dprintf("pict_type=%d number=%d\n", s->pict_type, s->picture_number);

    avctx->pict_type= s->pict_type;
    avctx->key_frame= s->pict_type == I_TYPE;

    skip_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)
            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)
            return -1;
        s->mpeg_f_code[1][0] = f_code;
        s->mpeg_f_code[1][1] = f_code;
    }
    s->y_dc_scale = 8;
    s->c_dc_scale = 8;
    s->first_slice = 1;
    return 0;
}

static void mpeg_decode_sequence_extension(MpegEncContext *s)
{
    int horiz_size_ext, vert_size_ext;
    int bit_rate_ext, vbv_buf_ext, low_delay;
    int frame_rate_ext_n, frame_rate_ext_d;

    skip_bits(&s->gb, 8); /* profil and level */
    s->progressive_sequence = get_bits1(&s->gb); /* progressive_sequence */
    skip_bits(&s->gb, 2); /* chroma_format */
    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 = ((s->bit_rate / 400) | (bit_rate_ext << 12)) * 400;
    skip_bits1(&s->gb); /* marker */
    vbv_buf_ext = get_bits(&s->gb, 8);
    low_delay = get_bits1(&s->gb);
    frame_rate_ext_n = get_bits(&s->gb, 2);
    frame_rate_ext_d = get_bits(&s->gb, 5);
    if (frame_rate_ext_d >= 1)
        s->frame_rate = (s->frame_rate * frame_rate_ext_n) / frame_rate_ext_d;
    dprintf("sequence extension\n");
    s->mpeg2 = 1;
    s->avctx->sub_id = 2; /* indicates mpeg2 found */
}

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

    dprintf("matrix extension\n");

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

static void mpeg_decode_picture_coding_extension(MpegEncContext *s)
{
    s->full_pel[0] = s->full_pel[1] = 0;
    s->mpeg_f_code[0][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[0][1] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][0] = get_bits(&s->gb, 4);
    s->mpeg_f_code[1][1] = get_bits(&s->gb, 4);
    s->intra_dc_precision = get_bits(&s->gb, 2);
    s->picture_structure = get_bits(&s->gb, 2);
    s->top_field_first = get_bits1(&s->gb);
    s->frame_pred_frame_dct = get_bits1(&s->gb);
    s->concealment_motion_vectors = get_bits1(&s->gb);
    s->q_scale_type = get_bits1(&s->gb);
    s->intra_vlc_format = get_bits1(&s->gb);
    s->alternate_scan = get_bits1(&s->gb);
    s->repeat_first_field = get_bits1(&s->gb);
    s->chroma_420_type = get_bits1(&s->gb);
    s->progressive_frame = get_bits1(&s->gb);
    
    if(s->alternate_scan){
        ff_init_scantable(s, &s->inter_scantable  , ff_alternate_vertical_scan);
        ff_init_scantable(s, &s->intra_scantable  , ff_alternate_vertical_scan);
        ff_init_scantable(s, &s->intra_h_scantable, ff_alternate_vertical_scan);
        ff_init_scantable(s, &s->intra_v_scantable, ff_alternate_vertical_scan);
    }else{
        ff_init_scantable(s, &s->inter_scantable  , ff_zigzag_direct);
        ff_init_scantable(s, &s->intra_scantable  , ff_zigzag_direct);
        ff_init_scantable(s, &s->intra_h_scantable, ff_alternate_horizontal_scan);
        ff_init_scantable(s, &s->intra_v_scantable, ff_alternate_vertical_scan);
    }
    
    /* composite display not parsed */
    dprintf("intra_dc_precision=%d\n", s->intra_dc_precision);
    dprintf("picture_structure=%d\n", s->picture_structure);
    dprintf("top field first=%d\n", s->top_field_first);
    dprintf("repeat first field=%d\n", s->repeat_first_field);
    dprintf("conceal=%d\n", s->concealment_motion_vectors);
    dprintf("intra_vlc_format=%d\n", s->intra_vlc_format);
    dprintf("alternate_scan=%d\n", s->alternate_scan);
    dprintf("frame_pred_frame_dct=%d\n", s->frame_pred_frame_dct);
    dprintf("progressive_frame=%d\n", s->progressive_frame);
}

static void mpeg_decode_extension(AVCodecContext *avctx, 
                                  UINT8 *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ext_type;

    init_get_bits(&s->gb, buf, buf_size);
    
    ext_type = get_bits(&s->gb, 4);
    switch(ext_type) {
    case 0x1:
        /* sequence ext */
        mpeg_decode_sequence_extension(s);
        break;
    case 0x3:
        /* quant matrix extension */
        mpeg_decode_quant_matrix_extension(s);
        break;
    case 0x8:
        /* picture extension */
        mpeg_decode_picture_coding_extension(s);
        break;
    }
}

#define DECODE_SLICE_FATAL_ERROR -2
#define DECODE_SLICE_ERROR -1
#define DECODE_SLICE_OK 0
#define DECODE_SLICE_EOP 1

/**
 * decodes a slice.
 * @return DECODE_SLICE_FATAL_ERROR if a non recoverable error occured<br>
 *         DECODE_SLICE_ERROR if the slice is damaged<br>
 *         DECODE_SLICE_OK if this slice is ok<br>
 *         DECODE_SLICE_EOP if the end of the picture is reached
 */
static int mpeg_decode_slice(AVCodecContext *avctx, 
                              AVPicture *pict,
                              int start_code,
                              UINT8 *buf, int buf_size)
{
    Mpeg1Context *s1 = avctx->priv_data;
    MpegEncContext *s = &s1->mpeg_enc_ctx;
    int ret;

    start_code = (start_code - 1) & 0xff;
    if (start_code >= s->mb_height){