dc = get_bits(&gb, 9); dc = (dc << (32 - 9)) >> (32 - 9);
dc = get_sbits(&gb, 9);
static inline void dv_decode_video_segment(DVVideoContext *s,                                            uint8_t *buf_ptr1,                                            const uint16_t *mb_pos_ptr){    int quant, dc, dct_mode, class1, j;    int mb_index, mb_x, mb_y, v, last_index;    DCTELEM *block, *block1;    int c_offset;    uint8_t *y_ptr;    void (*idct_put)(uint8_t *dest, int line_size, DCTELEM *block);    uint8_t *buf_ptr;    PutBitContext pb, vs_pb;    GetBitContext gb;    BlockInfo mb_data[5 * 6], *mb, *mb1;    DCTELEM sblock[5*6][64] __align8;    uint8_t mb_bit_buffer[80 + 4]; /* allow some slack */    uint8_t vs_bit_buffer[5 * 80 + 4]; /* allow some slack */	        memset(sblock, 0, sizeof(sblock));    /* pass 1 : read DC and AC coefficients in blocks */    buf_ptr = buf_ptr1;    block1 = &sblock[0][0];    mb1 = mb_data;    init_put_bits(&vs_pb, vs_bit_buffer, 5 * 80);    for(mb_index = 0; mb_index < 5; mb_index++, mb1 += 6, block1 += 6 * 64) {        /* skip header */        quant = buf_ptr[3] & 0x0f;        buf_ptr += 4;        init_put_bits(&pb, mb_bit_buffer, 80);        mb = mb1;        block = block1;        for(j = 0;j < 6; j++) {            last_index = block_sizes[j];	    init_get_bits(&gb, buf_ptr, last_index);                        /* get the dc */            dc = get_bits(&gb, 9);            dc = (dc << (32 - 9)) >> (32 - 9);            dct_mode = get_bits1(&gb);            mb->dct_mode = dct_mode;            mb->scan_table = s->dv_zigzag[dct_mode];            class1 = get_bits(&gb, 2);            mb->shift_table = s->dv_idct_shift[class1 == 3][dct_mode]                [quant + dv_quant_offset[class1]];            dc = dc << 2;            /* convert to unsigned because 128 is not added in the               standard IDCT */            dc += 1024;            block[0] = dc;            buf_ptr += last_index >> 3;            mb->pos = 0;            mb->partial_bit_count = 0;#ifdef VLC_DEBUG            printf("MB block: %d, %d ", mb_index, j);#endif            dv_decode_ac(&gb, mb, block);            /* write the remaining bits  in a new buffer only if the               block is finished */            if (mb->pos >= 64)                bit_copy(&pb, &gb);                        block += 64;            mb++;        }                /* pass 2 : we can do it just after */#ifdef VLC_DEBUG        printf("***pass 2 size=%d MB#=%d\n", put_bits_count(&pb), mb_index);#endif        block = block1;        mb = mb1;        init_get_bits(&gb, mb_bit_buffer, put_bits_count(&pb));	flush_put_bits(&pb);        for(j = 0;j < 6; j++, block += 64, mb++) {            if (mb->pos < 64 && get_bits_left(&gb) > 0) {                dv_decode_ac(&gb, mb, block);                /* if still not finished, no need to parse other blocks */                if (mb->pos < 64)                    break;            }        }        /* all blocks are finished, so the extra bytes can be used at           the video segment level */        if (j >= 6)	    bit_copy(&vs_pb, &gb);    }    /* we need a pass other the whole video segment */#ifdef VLC_DEBUG    printf("***pass 3 size=%d\n", put_bits_count(&vs_pb));#endif    block = &sblock[0][0];    mb = mb_data;    init_get_bits(&gb, vs_bit_buffer, put_bits_count(&vs_pb));    flush_put_bits(&vs_pb);    for(mb_index = 0; mb_index < 5; mb_index++) {        for(j = 0;j < 6; j++) {            if (mb->pos < 64) {#ifdef VLC_DEBUG                printf("start %d:%d\n", mb_index, j);#endif                dv_decode_ac(&gb, mb, block);            }	    if (mb->pos >= 64 && mb->pos < 127)		av_log(NULL, AV_LOG_ERROR, "AC EOB marker is absent pos=%d\n", mb->pos);            block += 64;            mb++;        }    }        /* compute idct and place blocks */    block = &sblock[0][0];    mb = mb_data;    for(mb_index = 0; mb_index < 5; mb_index++) {        v = *mb_pos_ptr++;        mb_x = v & 0xff;        mb_y = v >> 8;        y_ptr = s->picture.data[0] + (mb_y * s->picture.linesize[0] * 8) + (mb_x * 8);        if (s->sys->pix_fmt == PIX_FMT_YUV411P)            c_offset = (mb_y * s->picture.linesize[1] * 8) + ((mb_x >> 2) * 8);        else            c_offset = ((mb_y >> 1) * s->picture.linesize[1] * 8) + ((mb_x >> 1) * 8);        for(j = 0;j < 6; j++) {            idct_put = s->idct_put[mb->dct_mode];            if (j < 4) {                if (s->sys->pix_fmt == PIX_FMT_YUV411P && mb_x < (704 / 8)) {                    /* NOTE: at end of line, the macroblock is handled as 420 */                    idct_put(y_ptr + (j * 8), s->picture.linesize[0], block);                } else {                    idct_put(y_ptr + ((j & 1) * 8) + ((j >> 1) * 8 * s->picture.linesize[0]),                             s->picture.linesize[0], block);                }            } else {                if (s->sys->pix_fmt == PIX_FMT_YUV411P && mb_x >= (704 / 8)) {                    uint64_t aligned_pixels[64/8];                    uint8_t *pixels= (uint8_t*)aligned_pixels;		    uint8_t *c_ptr, *c_ptr1, *ptr;                    int y, linesize;                    /* NOTE: at end of line, the macroblock is handled as 420 */                    idct_put(pixels, 8, block);                    linesize = s->picture.linesize[6 - j];                    c_ptr = s->picture.data[6 - j] + c_offset;                    ptr = pixels;                    for(y = 0;y < 8; y++) {                        /* convert to 411P */                        c_ptr1 = c_ptr + 8*linesize;                        c_ptr[0]= ptr[0]; c_ptr1[0]= ptr[4];                        c_ptr[1]= ptr[1]; c_ptr1[1]= ptr[5];                        c_ptr[2]= ptr[2]; c_ptr1[2]= ptr[6];                        c_ptr[3]= ptr[3]; c_ptr1[3]= ptr[7];                        c_ptr += linesize;                        ptr += 8;                    }                } else {                    /* don't ask me why they inverted Cb and Cr ! */                    idct_put(s->picture.data[6 - j] + c_offset,                              s->picture.linesize[6 - j], block);                }            }            block += 64;            mb++;        }    }}