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

                x = 0;
                y = 0;
                for(j=0;j<n;j++) {
                    memset(s->block, 0, sizeof(s->block));
                    if (!s->progressive && decode_block(s, s->block, i,
                                     s->dc_index[i], s->ac_index[i],
                                     s->quant_matrixes[ s->quant_index[c] ]) < 0) {
                        av_log(s->avctx, AV_LOG_ERROR, "error y=%d x=%d\n", mb_y, mb_x);
                        return -1;
                    }
                    if (s->progressive && decode_block_progressive(s, s->block, i,
                                     s->dc_index[i], s->ac_index[i],
                                     s->quant_matrixes[ s->quant_index[c] ], ss, se, Ah, Al, &EOBRUN) < 0) {
                        av_log(s->avctx, AV_LOG_ERROR, "error y=%d x=%d\n", mb_y, mb_x);
                        return -1;
                    }
//                    av_log(s->avctx, AV_LOG_DEBUG, "mb: %d %d processed\n", mb_y, mb_x);
                    ptr = data[c] +
                        (((linesize[c] * (v * mb_y + y) * 8) +
                        (h * mb_x + x) * 8) >> s->avctx->lowres);
                    if (s->interlaced && s->bottom_field)
                        ptr += linesize[c] >> 1;
//av_log(NULL, AV_LOG_DEBUG, "%d %d %d %d %d %d %d %d \n", mb_x, mb_y, x, y, c, s->bottom_field, (v * mb_y + y) * 8, (h * mb_x + x) * 8);
                    if(!s->progressive)
                        s->dsp.idct_put(ptr, linesize[c], s->block);
                    else
                        s->dsp.idct_add(ptr, linesize[c], s->block);
                    if (++x == h) {
                        x = 0;
                        y++;
                    }
                }
            }
            /* (< 1350) buggy workaround for Spectralfan.mov, should be fixed */
            if (s->restart_interval && (s->restart_interval < 1350) &&
                !--s->restart_count) {
                align_get_bits(&s->gb);
                skip_bits(&s->gb, 16); /* skip RSTn */
                for (i=0; i<nb_components; i++) /* reset dc */
                    s->last_dc[i] = 1024;
            }
        }
    }
    return 0;
}

int ff_mjpeg_decode_sos(MJpegDecodeContext *s)
{
    int len, nb_components, i, h, v, predictor, point_transform;
    int vmax, hmax, index, id;
    const int block_size= s->lossless ? 1 : 8;
    int ilv, prev_shift;

    /* XXX: verify len field validity */
    len = get_bits(&s->gb, 16);
    nb_components = get_bits(&s->gb, 8);
    if (len != 6+2*nb_components)
    {
        av_log(s->avctx, AV_LOG_ERROR, "decode_sos: invalid len (%d)\n", len);
        return -1;
    }
    vmax = 0;
    hmax = 0;
    for(i=0;i<nb_components;i++) {
        id = get_bits(&s->gb, 8) - 1;
        av_log(s->avctx, AV_LOG_DEBUG, "component: %d\n", id);
        /* find component index */
        for(index=0;index<s->nb_components;index++)
            if (id == s->component_id[index])
                break;
        if (index == s->nb_components)
        {
            av_log(s->avctx, AV_LOG_ERROR, "decode_sos: index(%d) out of components\n", index);
            return -1;
        }

        s->comp_index[i] = index;

        s->nb_blocks[i] = s->h_count[index] * s->v_count[index];
        s->h_scount[i] = s->h_count[index];
        s->v_scount[i] = s->v_count[index];

        s->dc_index[i] = get_bits(&s->gb, 4);
        s->ac_index[i] = get_bits(&s->gb, 4);

        if (s->dc_index[i] <  0 || s->ac_index[i] < 0 ||
            s->dc_index[i] >= 4 || s->ac_index[i] >= 4)
            goto out_of_range;
#if 0 //buggy
        switch(s->start_code)
        {
            case SOF0:
                if (dc_index[i] > 1 || ac_index[i] > 1)
                    goto out_of_range;
                break;
            case SOF1:
            case SOF2:
                if (dc_index[i] > 3 || ac_index[i] > 3)
                    goto out_of_range;
                break;
            case SOF3:
                if (dc_index[i] > 3 || ac_index[i] != 0)
                    goto out_of_range;
                break;
        }
#endif
    }

    predictor= get_bits(&s->gb, 8); /* JPEG Ss / lossless JPEG predictor /JPEG-LS NEAR */
    ilv= get_bits(&s->gb, 8);    /* JPEG Se / JPEG-LS ILV */
    prev_shift = get_bits(&s->gb, 4); /* Ah */
    point_transform= get_bits(&s->gb, 4); /* Al */

    for(i=0;i<nb_components;i++)
        s->last_dc[i] = 1024;

    if (nb_components > 1) {
        /* interleaved stream */
        s->mb_width  = (s->width  + s->h_max * block_size - 1) / (s->h_max * block_size);
        s->mb_height = (s->height + s->v_max * block_size - 1) / (s->v_max * block_size);
    } else if(!s->ls) { /* skip this for JPEG-LS */
        h = s->h_max / s->h_scount[0];
        v = s->v_max / s->v_scount[0];
        s->mb_width  = (s->width  + h * block_size - 1) / (h * block_size);
        s->mb_height = (s->height + v * block_size - 1) / (v * block_size);
        s->nb_blocks[0] = 1;
        s->h_scount[0] = 1;
        s->v_scount[0] = 1;
    }

    if(s->avctx->debug & FF_DEBUG_PICT_INFO)
        av_log(s->avctx, AV_LOG_DEBUG, "%s %s p:%d >>:%d ilv:%d bits:%d %s\n", s->lossless ? "lossless" : "sequencial DCT", s->rgb ? "RGB" : "",
               predictor, point_transform, ilv, s->bits,
               s->pegasus_rct ? "PRCT" : (s->rct ? "RCT" : ""));


    /* mjpeg-b can have padding bytes between sos and image data, skip them */
    for (i = s->mjpb_skiptosod; i > 0; i--)
        skip_bits(&s->gb, 8);

    if(s->lossless){
        if(ENABLE_JPEGLS_DECODER && s->ls){
//            for(){
//            reset_ls_coding_parameters(s, 0);

            ff_jpegls_decode_picture(s, predictor, point_transform, ilv);
        }else{
            if(s->rgb){
                if(ljpeg_decode_rgb_scan(s, predictor, point_transform) < 0)
                    return -1;
            }else{
                if(ljpeg_decode_yuv_scan(s, predictor, point_transform) < 0)
                    return -1;
            }
        }
    }else{
        if(mjpeg_decode_scan(s, nb_components, predictor, ilv, prev_shift, point_transform) < 0)
            return -1;
    }
    emms_c();
    return 0;
 out_of_range:
    av_log(s->avctx, AV_LOG_ERROR, "decode_sos: ac/dc index out of range\n");
    return -1;
}

static int mjpeg_decode_dri(MJpegDecodeContext *s)
{
    if (get_bits(&s->gb, 16) != 4)
        return -1;
    s->restart_interval = get_bits(&s->gb, 16);
    s->restart_count = 0;
    av_log(s->avctx, AV_LOG_DEBUG, "restart interval: %d\n", s->restart_interval);

    return 0;
}

static int mjpeg_decode_app(MJpegDecodeContext *s)
{
    int len, id, i;

    len = get_bits(&s->gb, 16);
    if (len < 5)
        return -1;
    if(8*len + get_bits_count(&s->gb) > s->gb.size_in_bits)
        return -1;

    id = (get_bits(&s->gb, 16) << 16) | get_bits(&s->gb, 16);
    id = be2me_32(id);
    len -= 6;

    if(s->avctx->debug & FF_DEBUG_STARTCODE){
        av_log(s->avctx, AV_LOG_DEBUG, "APPx %8X\n", id);
    }

    /* buggy AVID, it puts EOI only at every 10th frame */
    /* also this fourcc is used by non-avid files too, it holds some
       informations, but it's always present in AVID creates files */
    if (id == ff_get_fourcc("AVI1"))
    {
        /* structure:
            4bytes      AVI1
            1bytes      polarity
            1bytes      always zero
            4bytes      field_size
            4bytes      field_size_less_padding
        */
            s->buggy_avid = 1;
//        if (s->first_picture)
//            printf("mjpeg: workarounding buggy AVID\n");
        i = get_bits(&s->gb, 8);
        if     (i==2) s->bottom_field= 1;
        else if(i==1) s->bottom_field= 0;
#if 0
        skip_bits(&s->gb, 8);
        skip_bits(&s->gb, 32);
        skip_bits(&s->gb, 32);
        len -= 10;
#endif
//        if (s->interlace_polarity)
//            printf("mjpeg: interlace polarity: %d\n", s->interlace_polarity);
        goto out;
    }

//    len -= 2;

    if (id == ff_get_fourcc("JFIF"))
    {
        int t_w, t_h, v1, v2;
        skip_bits(&s->gb, 8); /* the trailing zero-byte */
        v1= get_bits(&s->gb, 8);
        v2= get_bits(&s->gb, 8);
        skip_bits(&s->gb, 8);

        s->avctx->sample_aspect_ratio.num= get_bits(&s->gb, 16);
        s->avctx->sample_aspect_ratio.den= get_bits(&s->gb, 16);

        if (s->avctx->debug & FF_DEBUG_PICT_INFO)
            av_log(s->avctx, AV_LOG_INFO, "mjpeg: JFIF header found (version: %x.%x) SAR=%d/%d\n",
                v1, v2,
                s->avctx->sample_aspect_ratio.num,
                s->avctx->sample_aspect_ratio.den
            );

        t_w = get_bits(&s->gb, 8);
        t_h = get_bits(&s->gb, 8);
        if (t_w && t_h)
        {
            /* skip thumbnail */
            if (len-10-(t_w*t_h*3) > 0)
                len -= t_w*t_h*3;
        }
        len -= 10;
        goto out;
    }

    if (id == ff_get_fourcc("Adob") && (get_bits(&s->gb, 8) == 'e'))
    {
        if (s->avctx->debug & FF_DEBUG_PICT_INFO)
            av_log(s->avctx, AV_LOG_INFO, "mjpeg: Adobe header found\n");
        skip_bits(&s->gb, 16); /* version */
        skip_bits(&s->gb, 16); /* flags0 */
        skip_bits(&s->gb, 16); /* flags1 */
        skip_bits(&s->gb, 8);  /* transform */
        len -= 7;
        goto out;
    }

    if (id == ff_get_fourcc("LJIF")){
        if (s->avctx->debug & FF_DEBUG_PICT_INFO)
            av_log(s->avctx, AV_LOG_INFO, "Pegasus lossless jpeg header found\n");
        skip_bits(&s->gb, 16); /* version ? */
        skip_bits(&s->gb, 16); /* unknwon always 0? */
        skip_bits(&s->gb, 16); /* unknwon always 0? */
        skip_bits(&s->gb, 16); /* unknwon always 0? */
        switch( get_bits(&s->gb, 8)){
        case 1:
            s->rgb= 1;
            s->pegasus_rct=0;
            break;
        case 2:
            s->rgb= 1;
            s->pegasus_rct=1;
            break;
        default:
            av_log(s->avctx, AV_LOG_ERROR, "unknown colorspace\n");
        }
        len -= 9;
        goto out;
    }

    /* Apple MJPEG-A */
    if ((s->start_code == APP1) && (len > (0x28 - 8)))
    {
        id = (get_bits(&s->gb, 16) << 16) | get_bits(&s->gb, 16);
        id = be2me_32(id);
        len -= 4;
        if (id == ff_get_fourcc("mjpg")) /* Apple MJPEG-A */
        {
#if 0
            skip_bits(&s->gb, 32); /* field size */
            skip_bits(&s->gb, 32); /* pad field size */
            skip_bits(&s->gb, 32); /* next off */
            skip_bits(&s->gb, 32); /* quant off */
            skip_bits(&s->gb, 32); /* huff off */
            skip_bits(&s->gb, 32); /* image off */
            skip_bits(&s->gb, 32); /* scan off */
            skip_bits(&s->gb, 32); /* data off */
#endif
            if (s->avctx->debug & FF_DEBUG_PICT_INFO)
                av_log(s->avctx, AV_LOG_INFO, "mjpeg: Apple MJPEG-A header found\n");
        }
    }

out:
    /* slow but needed for extreme adobe jpegs */
    if (len < 0)
        av_log(s->avctx, AV_LOG_ERROR, "mjpeg: error, decode_app parser read over the end\n");
    while(--len > 0)
        skip_bits(&s->gb, 8);

    return 0;
}

static int mjpeg_decode_com(MJpegDecodeContext *s)
{
    int len = get_bits(&s->gb, 16);
    if (len >= 2 && 8*len - 16 + get_bits_count(&s->gb) <= s->gb.size_in_bits) {
        char *cbuf = av_malloc(len - 1);
        if (cbuf) {
            int i;
            for (i = 0; i < len - 2; i++)
                cbuf[i] = get_bits(&s->gb, 8);
            if (i > 0 && cbuf[i-1] == '\n')
                cbuf[i-1] = 0;
            else
                cbuf[i] = 0;

            if(s->avctx->debug & FF_DEBUG_PICT_INFO)
                av_log(s->avctx, AV_LOG_INFO, "mjpeg comment: '%s'\n", cbuf);

            /* buggy avid, it puts EOI only at every 10th frame */
            if (!strcmp(cbuf, "AVID"))
            {
                s->buggy_avid = 1;