mjpeg.c

ffmpeg源码分析

                if(ljpeg_decode_yuv_scan(s, predictor, point_transform) < 0)
                    return -1;
            }
        }
    }else{
        if(mjpeg_decode_scan(s) < 0)
            return -1;
    }
    emms_c();
    return 0;
 out_of_range:
    dprintf("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;
    dprintf("restart interval: %d\n", s->restart_interval);

    return 0;
}

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

    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");
        s->interlace_polarity = get_bits(&s->gb, 8);
#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) {
        uint8_t *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;
                //        if (s->first_picture)
                //            printf("mjpeg: workarounding buggy AVID\n");
            }
            else if(!strcmp(cbuf, "CS=ITU601")){
                s->cs_itu601= 1;
            }

            av_free(cbuf);
        }
    }

    return 0;
}

#if 0
static int valid_marker_list[] =
{
        /* 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f */
/* 0 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 1 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 2 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 3 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 4 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 5 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 6 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 7 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 8 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 9 */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* a */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* b */    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* c */    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
/* d */    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
/* e */    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
/* f */    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,
}
#endif

/* return the 8 bit start code value and update the search
   state. Return -1 if no start code found */
static int find_marker(uint8_t **pbuf_ptr, uint8_t *buf_end)
{
    uint8_t *buf_ptr;
    unsigned int v, v2;
    int val;
#ifdef DEBUG
    int skipped=0;
#endif

    buf_ptr = *pbuf_ptr;
    while (buf_ptr < buf_end) {
        v = *buf_ptr++;
        v2 = *buf_ptr;
        if ((v == 0xff) && (v2 >= 0xc0) && (v2 <= 0xfe) && buf_ptr < buf_end) {
            val = *buf_ptr++;
            goto found;
        }
#ifdef DEBUG
        skipped++;
#endif
    }
    val = -1;
found:
#ifdef DEBUG
    dprintf("find_marker skipped %d bytes\n", skipped);
#endif
    *pbuf_ptr = buf_ptr;
    return val;
}

static int mjpeg_decode_frame(AVCodecContext *avctx,
                              void *data, int *data_size,
                              uint8_t *buf, int buf_size)
{
    MJpegDecodeContext *s = avctx->priv_data;
    uint8_t *buf_end, *buf_ptr;
    int start_code;
    AVFrame *picture = data;

    buf_ptr = buf;
    buf_end = buf + buf_size;
    while (buf_ptr < buf_end) {
        /* find start next marker */
        start_code = find_marker(&buf_ptr, buf_end);
        {
            /* EOF */
            if (start_code < 0) {
                goto the_end;
            } else {
                dprintf("marker=%x avail_size_in_buf=%d\n", start_code, buf_end - buf_ptr);

                if ((buf_end - buf_ptr) > s->buffer_size)
                {
                    av_free(s->buffer);
                    s->buffer_size = buf_end-buf_ptr;
                    s->buffer = av_malloc(s->buffer_size + FF_INPUT_BUFFER_PADDING_SIZE);
                    dprintf("buffer too small, expanding to %d bytes\n",
                        s->buffer_size);
                }

                /* unescape buffer of SOS, use special treatment for JPEG-LS */
                if (start_code == SOS && !s->ls)
                {
                    uint8_t *src = buf_ptr;
                    uint8_t *dst = s->buffer;

                    while (src<buf_end)
                    {
                        uint8_t x = *(src++);

                        *(dst++) = x;
                        if (x == 0xff)
                        {
                            while(src<buf_end && x == 0xff)
                                x = *(src++);

                            if (x >= 0xd0 && x <= 0xd7)
                                *(dst++) = x;
                            else if (x)
                                break;
                        }
                    }
                    init_get_bits(&s->gb, s->buffer, (dst - s->buffer)*8);

                    dprintf("escaping removed %d bytes\n",
                        (buf_end - buf_ptr) - (dst - s->buffer));
                }
                else if(start_code == SOS && s->ls){
                    uint8_t *src = buf_ptr;
                    uint8_t *dst = s->buffer;
                    int bit_count = 0;
                    int t = 0, b = 0;
                    PutBitContext pb;

                    s->cur_scan++;

                    /* find marker */
                    while (src + t < buf_end){
                        uint8_t x = src[t++];
                        if (x == 0xff){
                            while((src + t < buf_end) && x == 0xff)
                                x = src[t++];
                            if (x & 0x80) {
                                t -= 2;
                                break;
                            }
                        }
                    }
                    bit_count = t * 8;

                    init_put_bits(&pb, dst, t);

                    /* unescape bitstream */
                    while(b < t){
                        uint8_t x = src[b++];
                        put_bits(&pb, 8, x);
                        if(x == 0xFF){
                            x = src[b++];
                            put_bits(&pb, 7, x);
                            bit_count--;
                        }
                    }
                    flush_put_bits(&pb);

                    init_get_bits(&s->gb, dst, bit_count);
                }
                else
                    init_get_bits(&s->gb, buf_ptr, (buf_end - buf_ptr)*8);

                s->start_code = start_code;
                if(s->avctx->debug & FF_DEBUG_STARTCODE){
                    av_log(s->avctx, AV_LOG_DEBUG, "startcode: %X\n", start_code);
                }

                /* process markers */
                if (start_code >= 0xd0 && start_code <= 0xd7) {
                    dprintf("restart marker: %d\n", start_code&0x0f);
                    /* APP fields */
                } else if (start_code >= APP0 && start_code <= APP15) {
                    mjpeg_decode_app(s);
                    /* Comment */
                } else if (start_code == COM){
                    mjpeg_decode_com(s);
                }

                switch(start_code) {
                case SOI:
                    s->restart_interval = 0;

                    s->restart_count = 0;
                    /* nothing to do on SOI */
                    break;
                case DQT:
                    mjpeg_decode_dqt(s);
                    break;
                case DHT:
                    if(mjpeg_decode_dht(s) < 0){
                        av_log(s->avctx, AV_LOG_ERROR, "huffman table decode error\n");
                        return -1;
                    }
                    break;
                case SOF0:
                    s->lossless=0;
                    if (mjpeg_decode_sof(s) < 0)
                        return -1;
                    break;
                case SOF3:
                    s->lossless=1;
                    if (mjpeg_decode_sof(s) < 0)
                        return -1;
                    break;
                case SOF48: