mjpegdec.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

        av_log(s->avctx, AV_LOG_DEBUG, "decode_sof0: error, len(%d) mismatch\n", len);
    }

    /* totally blank picture as progressive JPEG will only add details to it */
    if(s->progressive){
        memset(s->picture.data[0], 0, s->picture.linesize[0] * s->height);
        memset(s->picture.data[1], 0, s->picture.linesize[1] * s->height >> (s->v_max - s->v_count[1]));
        memset(s->picture.data[2], 0, s->picture.linesize[2] * s->height >> (s->v_max - s->v_count[2]));
    }
    return 0;
}

static inline int mjpeg_decode_dc(MJpegDecodeContext *s, int dc_index)
{
    int code;
    code = get_vlc2(&s->gb, s->vlcs[0][dc_index].table, 9, 2);
    if (code < 0)
    {
        av_log(s->avctx, AV_LOG_WARNING, "mjpeg_decode_dc: bad vlc: %d:%d (%p)\n", 0, dc_index,
               &s->vlcs[0][dc_index]);
        return 0xffff;
    }

    if(code)
        return get_xbits(&s->gb, code);
    else
        return 0;
}

/* decode block and dequantize */
static int decode_block(MJpegDecodeContext *s, DCTELEM *block,
                        int component, int dc_index, int ac_index, int16_t *quant_matrix)
{
    int code, i, j, level, val;

    /* DC coef */
    val = mjpeg_decode_dc(s, dc_index);
    if (val == 0xffff) {
        av_log(s->avctx, AV_LOG_ERROR, "error dc\n");
        return -1;
    }
    val = val * quant_matrix[0] + s->last_dc[component];
    s->last_dc[component] = val;
    block[0] = val;
    /* AC coefs */
    i = 0;
    {OPEN_READER(re, &s->gb)
    for(;;) {
        UPDATE_CACHE(re, &s->gb);
        GET_VLC(code, re, &s->gb, s->vlcs[1][ac_index].table, 9, 2)

        /* EOB */
        if (code == 0x10)
            break;
        i += ((unsigned)code) >> 4;
        if(code != 0x100){
            code &= 0xf;
            if(code > MIN_CACHE_BITS - 16){
                UPDATE_CACHE(re, &s->gb)
            }
            {
                int cache=GET_CACHE(re,&s->gb);
                int sign=(~cache)>>31;
                level = (NEG_USR32(sign ^ cache,code) ^ sign) - sign;
            }

            LAST_SKIP_BITS(re, &s->gb, code)

            if (i >= 63) {
                if(i == 63){
                    j = s->scantable.permutated[63];
                    block[j] = level * quant_matrix[j];
                    break;
                }
                av_log(s->avctx, AV_LOG_ERROR, "error count: %d\n", i);
                return -1;
            }
            j = s->scantable.permutated[i];
            block[j] = level * quant_matrix[j];
        }
    }
    CLOSE_READER(re, &s->gb)}

    return 0;
}

/* decode block and dequantize - progressive JPEG version */
static int decode_block_progressive(MJpegDecodeContext *s, DCTELEM *block,
                        int component, int dc_index, int ac_index, int16_t *quant_matrix,
                        int ss, int se, int Ah, int Al, int *EOBRUN)
{
    int code, i, j, level, val, run;

    /* DC coef */
    if(!ss){
        val = mjpeg_decode_dc(s, dc_index);
        if (val == 0xffff) {
            av_log(s->avctx, AV_LOG_ERROR, "error dc\n");
            return -1;
        }
        val = (val * quant_matrix[0] << Al) + s->last_dc[component];
    }else
        val = 0;
    s->last_dc[component] = val;
    block[0] = val;
    if(!se) return 0;
    /* AC coefs */
    if(*EOBRUN){
        (*EOBRUN)--;
        return 0;
    }
    {OPEN_READER(re, &s->gb)
    for(i=ss;;i++) {
        UPDATE_CACHE(re, &s->gb);
        GET_VLC(code, re, &s->gb, s->vlcs[1][ac_index].table, 9, 2)
        /* Progressive JPEG use AC coeffs from zero and this decoder sets offset 16 by default */
        code -= 16;
        if(code & 0xF) {
            i += ((unsigned) code) >> 4;
            code &= 0xf;
            if(code > MIN_CACHE_BITS - 16){
                UPDATE_CACHE(re, &s->gb)
            }
            {
                int cache=GET_CACHE(re,&s->gb);
                int sign=(~cache)>>31;
                level = (NEG_USR32(sign ^ cache,code) ^ sign) - sign;
            }

            LAST_SKIP_BITS(re, &s->gb, code)

            if (i >= se) {
                if(i == se){
                    j = s->scantable.permutated[se];
                    block[j] = level * quant_matrix[j] << Al;
                    break;
                }
                av_log(s->avctx, AV_LOG_ERROR, "error count: %d\n", i);
                return -1;
            }
            j = s->scantable.permutated[i];
            block[j] = level * quant_matrix[j] << Al;
        }else{
            run = ((unsigned) code) >> 4;
            if(run == 0xF){// ZRL - skip 15 coefficients
                i += 15;
            }else{
                val = run;
                run = (1 << run);
                UPDATE_CACHE(re, &s->gb);
                run += (GET_CACHE(re, &s->gb) >> (32 - val)) & (run - 1);
                if(val)
                    LAST_SKIP_BITS(re, &s->gb, val);
                *EOBRUN = run - 1;
                break;
            }
        }
    }
    CLOSE_READER(re, &s->gb)}

    return 0;
}

static int ljpeg_decode_rgb_scan(MJpegDecodeContext *s, int predictor, int point_transform){
    int i, mb_x, mb_y;
    uint16_t buffer[32768][4];
    int left[3], top[3], topleft[3];
    const int linesize= s->linesize[0];
    const int mask= (1<<s->bits)-1;

    if((unsigned)s->mb_width > 32768) //dynamic alloc
        return -1;

    for(i=0; i<3; i++){
        buffer[0][i]= 1 << (s->bits + point_transform - 1);
    }
    for(mb_y = 0; mb_y < s->mb_height; mb_y++) {
        const int modified_predictor= mb_y ? predictor : 1;
        uint8_t *ptr = s->picture.data[0] + (linesize * mb_y);

        if (s->interlaced && s->bottom_field)
            ptr += linesize >> 1;

        for(i=0; i<3; i++){
            top[i]= left[i]= topleft[i]= buffer[0][i];
        }
        for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
            if (s->restart_interval && !s->restart_count)
                s->restart_count = s->restart_interval;

            for(i=0;i<3;i++) {
                int pred;

                topleft[i]= top[i];
                top[i]= buffer[mb_x][i];

                PREDICT(pred, topleft[i], top[i], left[i], modified_predictor);

                left[i]=
                buffer[mb_x][i]= mask & (pred + (mjpeg_decode_dc(s, s->dc_index[i]) << point_transform));
            }

            if (s->restart_interval && !--s->restart_count) {
                align_get_bits(&s->gb);
                skip_bits(&s->gb, 16); /* skip RSTn */
            }
        }

        if(s->rct){
            for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
                ptr[4*mb_x+1] = buffer[mb_x][0] - ((buffer[mb_x][1] + buffer[mb_x][2] - 0x200)>>2);
                ptr[4*mb_x+0] = buffer[mb_x][1] + ptr[4*mb_x+1];
                ptr[4*mb_x+2] = buffer[mb_x][2] + ptr[4*mb_x+1];
            }
        }else if(s->pegasus_rct){
            for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
                ptr[4*mb_x+1] = buffer[mb_x][0] - ((buffer[mb_x][1] + buffer[mb_x][2])>>2);
                ptr[4*mb_x+0] = buffer[mb_x][1] + ptr[4*mb_x+1];
                ptr[4*mb_x+2] = buffer[mb_x][2] + ptr[4*mb_x+1];
            }
        }else{
            for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
                ptr[4*mb_x+0] = buffer[mb_x][0];
                ptr[4*mb_x+1] = buffer[mb_x][1];
                ptr[4*mb_x+2] = buffer[mb_x][2];
            }
        }
    }
    return 0;
}

static int ljpeg_decode_yuv_scan(MJpegDecodeContext *s, int predictor, int point_transform){
    int i, mb_x, mb_y;
    const int nb_components=3;

    for(mb_y = 0; mb_y < s->mb_height; mb_y++) {
        for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
            if (s->restart_interval && !s->restart_count)
                s->restart_count = s->restart_interval;

            if(mb_x==0 || mb_y==0 || s->interlaced){
                for(i=0;i<nb_components;i++) {
                    uint8_t *ptr;
                    int n, h, v, x, y, c, j, linesize;
                    n = s->nb_blocks[i];
                    c = s->comp_index[i];
                    h = s->h_scount[i];
                    v = s->v_scount[i];
                    x = 0;
                    y = 0;
                    linesize= s->linesize[c];

                    for(j=0; j<n; j++) {
                        int pred;

                        ptr = s->picture.data[c] + (linesize * (v * mb_y + y)) + (h * mb_x + x); //FIXME optimize this crap
                        if(y==0 && mb_y==0){
                            if(x==0 && mb_x==0){
                                pred= 128 << point_transform;
                            }else{
                                pred= ptr[-1];
                            }
                        }else{
                            if(x==0 && mb_x==0){
                                pred= ptr[-linesize];
                            }else{
                                PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);
                            }
                        }

                        if (s->interlaced && s->bottom_field)
                            ptr += linesize >> 1;
                        *ptr= pred + (mjpeg_decode_dc(s, s->dc_index[i]) << point_transform);

                        if (++x == h) {
                            x = 0;
                            y++;
                        }
                    }
                }
            }else{
                for(i=0;i<nb_components;i++) {
                    uint8_t *ptr;
                    int n, h, v, x, y, c, j, linesize;
                    n = s->nb_blocks[i];
                    c = s->comp_index[i];
                    h = s->h_scount[i];
                    v = s->v_scount[i];
                    x = 0;
                    y = 0;
                    linesize= s->linesize[c];

                    for(j=0; j<n; j++) {
                        int pred;

                        ptr = s->picture.data[c] + (linesize * (v * mb_y + y)) + (h * mb_x + x); //FIXME optimize this crap
                        PREDICT(pred, ptr[-linesize-1], ptr[-linesize], ptr[-1], predictor);
                        *ptr= pred + (mjpeg_decode_dc(s, s->dc_index[i]) << point_transform);
                        if (++x == h) {
                            x = 0;
                            y++;
                        }
                    }
                }
            }
            if (s->restart_interval && !--s->restart_count) {
                align_get_bits(&s->gb);
                skip_bits(&s->gb, 16); /* skip RSTn */
            }
        }
    }
    return 0;
}

static int mjpeg_decode_scan(MJpegDecodeContext *s, int nb_components, int ss, int se, int Ah, int Al){
    int i, mb_x, mb_y;
    int EOBRUN = 0;
    uint8_t* data[MAX_COMPONENTS];
    int linesize[MAX_COMPONENTS];

    if(Ah) return 0; /* TODO decode refinement planes too */

    for(i=0; i < nb_components; i++) {
        int c = s->comp_index[i];
        data[c] = s->picture.data[c];
        linesize[c]=s->linesize[c];
        if(s->avctx->codec->id==CODEC_ID_AMV) {
            //picture should be flipped upside-down for this codec
            data[c] += (linesize[c] * (s->v_scount[i] * 8 * s->mb_height - 1));
            linesize[c] *= -1;
        }
    }

    for(mb_y = 0; mb_y < s->mb_height; mb_y++) {
        for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
            if (s->restart_interval && !s->restart_count)
                s->restart_count = s->restart_interval;

            for(i=0;i<nb_components;i++) {
                uint8_t *ptr;
                int n, h, v, x, y, c, j;
                n = s->nb_blocks[i];
                c = s->comp_index[i];
                h = s->h_scount[i];
                v = s->v_scount[i];