mjpeg.c

                n = nb_blocks[i];
                c = comp_index[i];
                h = h_count[i];
                v = v_count[i];
                x = 0;
                y = 0;
		if (s->restart_interval && !s->restart_count)
		    s->restart_count = s->restart_interval;
                for(j=0;j<n;j++) {
                    memset(s->block, 0, sizeof(s->block));
                    if (decode_block(s, s->block, i, 
                                     dc_index[i], ac_index[i], 
                                     s->quant_index[c]) < 0) {
                        dprintf("error y=%d x=%d\n", mb_y, mb_x);
                        ret = -1;
                        goto the_end;
                    }
//		    dprintf("mb: %d %d processed\n", mb_y, mb_x);
                    ptr = s->current_picture[c] + 
                        (s->linesize[c] * (v * mb_y + y) * 8) + 
                        (h * mb_x + x) * 8;
                    if (s->interlaced && s->bottom_field)
                        ptr += s->linesize[c] >> 1;
                    ff_idct_put(ptr, s->linesize[c], s->block);
                    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 */
                for (j=0; j<nb_components; j++) /* reset dc */
                    s->last_dc[j] = 1024;
            }
        }
    }
    ret = 0;
 the_end:
    emms_c();
    return ret;
 out_of_range:
    dprintf("decode_sos: ac/dc index out of range\n");
    return -1;
}

static int mjpeg_decode_dri(MJpegDecodeContext *s,
                             UINT8 *buf, int buf_size)
{
    init_get_bits(&s->gb, buf, buf_size);

    if (get_bits(&s->gb, 16) != 4)
	return -1;
    s->restart_interval = get_bits(&s->gb, 16);
    dprintf("restart interval: %d\n", s->restart_interval);

    return 0;
}

#define FOURCC(a,b,c,d) ((a << 24) | (b << 16) | (c << 8) | d)
static int mjpeg_decode_app(MJpegDecodeContext *s,
                             UINT8 *buf, int buf_size, int start_code)
{
    int len, id;

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

    /* XXX: verify len field validity */
    len = get_bits(&s->gb, 16);
    if (len < 5)
	return -1;

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

    /* buggy AVID, it puts EOI only at every 10th frame */
    /* also this fourcc is used by non-avid files too, it means
       interleaving, but it's always present in AVID files */
    if (id == FOURCC('A','V','I','1'))
    {
	/* 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->interleaved_rows = 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->interleaved_rows)
	    printf("mjpeg: interleaved rows: %d\n", s->interleaved_rows);
	goto out;
    }
    
    len -= 2;
    
    if (id == FOURCC('J','F','I','F'))
    {
	skip_bits(&s->gb, 8); /* the trailing zero-byte */
	printf("mjpeg: JFIF header found (version: %x.%x)\n",
	    get_bits(&s->gb, 8), get_bits(&s->gb, 8));
	if (get_bits(&s->gb, 8) == 0)
	{
	    s->avctx->aspect_ratio_info = FF_ASPECT_EXTENDED;
	    s->avctx->aspected_width = get_bits(&s->gb, 16);
	    s->avctx->aspected_height = get_bits(&s->gb, 16);
	}
	else
	{
	    skip_bits(&s->gb, 16);
	    skip_bits(&s->gb, 16);
	}
	skip_bits(&s->gb, 8);
	skip_bits(&s->gb, 8);
	goto out;
    }
    
    /* Apple MJPEG-A */
    if ((start_code == APP1) && (len > (0x28 - 8)))
    {
	id = (get_bits(&s->gb, 16) << 16) | get_bits(&s->gb, 16);
	len -= 4;
        if (id == FOURCC('m','j','p','g')) /* 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->first_picture)
		printf("mjpeg: Apple MJPEG-A header found\n");
	}
    }

out:
    /* should check for further values.. */
    SKIP_REMAINING(&s->gb, len);

    return 0;
}
#undef FOURCC

static int mjpeg_decode_com(MJpegDecodeContext *s,
                             UINT8 *buf, int buf_size)
{
    int len, i;
    UINT8 *cbuf;

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

    /* XXX: verify len field validity */
    len = get_bits(&s->gb, 16)-2;
    cbuf = av_malloc(len+1);

    for (i = 0; i < len; i++)
	cbuf[i] = get_bits(&s->gb, 8);
    if (cbuf[i-1] == '\n')
	cbuf[i-1] = 0;
    else
	cbuf[i] = 0;

    printf("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");
    }
    
    av_free(cbuf);

    return 0;
}

/* return the 8 bit start code value and update the search
   state. Return -1 if no start code found */
static int find_marker(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;
retry:
    if (state) {
        /* get marker */
    found:
        if (buf_ptr < buf_end) {
            val = *buf_ptr++;
            state = 0;
            if ((val >= RST0) && (val <= RST7))
                goto retry;
        } else {
            val = -1;
        }
    } else {
        while (buf_ptr < buf_end) {
            v = *buf_ptr++;
            if (v == 0xff) {
                state = 1;
                goto found;
            }
        }
        val = -1;
    }
    *pbuf_ptr = buf_ptr;
    *header_state = state;
    return val;
}

static int mjpeg_decode_frame(AVCodecContext *avctx, 
                              void *data, int *data_size,
                              UINT8 *buf, int buf_size)
{
    MJpegDecodeContext *s = avctx->priv_data;
    UINT8 *buf_end, *buf_ptr, *buf_start;
    int len, code, input_size, i;
    AVPicture *picture = data;
    unsigned int start_code;

    *data_size = 0;

    /* no supplementary picture */
    if (buf_size == 0)
        return 0;

    buf_ptr = buf;
    buf_end = buf + buf_size;
    while (buf_ptr < buf_end) {
        buf_start = buf_ptr;
        /* find start next marker */
        code = find_marker(&buf_ptr, buf_end, &s->header_state);
        /* copy to buffer */
        len = buf_ptr - buf_start;
        if (len + (s->buf_ptr - s->buffer) > s->buffer_size) {
            /* data too big : flush */
            s->buf_ptr = s->buffer;
            if (code > 0)
                s->start_code = code;
        } else {
            memcpy(s->buf_ptr, buf_start, len);
            s->buf_ptr += len;
            if (code < 0) {
                /* nothing to do: wait next marker */
            } else if (code == 0 || code == 0xff) {
                /* if we got FF 00, we copy FF to the stream to unescape FF 00 */
                /* valid marker code is between 00 and ff - alex */
                s->buf_ptr--;
            } else {
                /* prepare data for next start code */
                input_size = s->buf_ptr - s->buffer;
                start_code = s->start_code;
                s->buf_ptr = s->buffer;
                s->start_code = code;
                dprintf("marker=%x\n", start_code);
                switch(start_code) {
                case SOI:
		    s->restart_interval = 0;
                    /* nothing to do on SOI */
                    break;
                case DQT:
                    mjpeg_decode_dqt(s, s->buffer, input_size);
                    break;
                case DHT:
                    mjpeg_decode_dht(s, s->buffer, input_size);
                    break;
                case SOF0:
                    mjpeg_decode_sof0(s, s->buffer, input_size);
                    break;
                case SOS:
                    mjpeg_decode_sos(s, s->buffer, input_size);
                    if (s->start_code == EOI || s->buggy_avid || s->restart_interval) {
                        int l;
                        if (s->interlaced) {
                            s->bottom_field ^= 1;
                            /* if not bottom field, do not output image yet */
                            if (s->bottom_field)
                                goto not_the_end;
                        }
                        for(i=0;i<3;i++) {
                            picture->data[i] = s->current_picture[i];
                            l = s->linesize[i];
                            if (s->interlaced)
                                l >>= 1;
                            picture->linesize[i] = l;
                        }
                        *data_size = sizeof(AVPicture);
                        avctx->height = s->height;
                        if (s->interlaced)
                            avctx->height *= 2;
                        avctx->width = s->width;
                        /* XXX: not complete test ! */
                        switch((s->h_count[0] << 4) | s->v_count[0]) {
                        case 0x11:
                            avctx->pix_fmt = PIX_FMT_YUV444P;
                            break;
                        case 0x21:
                            avctx->pix_fmt = PIX_FMT_YUV422P;
                            break;
                        default:
                        case 0x22:
                            avctx->pix_fmt = PIX_FMT_YUV420P;
                            break;
                        }
                        /* dummy quality */
                        /* XXX: infer it with matrix */
                    	avctx->quality = 3; 
                        goto the_end;
                    }
                    break;
		case DRI:
		    mjpeg_decode_dri(s, s->buffer, input_size);
		    break;
		case SOF1:
		case SOF2:
		case SOF3:
		case SOF5:
		case SOF6:
		case SOF7:
		case SOF9:
		case SOF10:
		case SOF11:
		case SOF13:
		case SOF14:
		case SOF15:
		case JPG:
		    printf("mjpeg: unsupported coding type (%x)\n", start_code);
		    return -1;
                }
#if 1
		if (start_code >= 0xd0 && start_code <= 0xd7) {
		    dprintf("restart marker: %d\n", start_code&0x0f);
		} else if (s->first_picture) {
		    /* APP fields */
		    if (start_code >= 0xe0 && start_code <= 0xef)
			mjpeg_decode_app(s, s->buffer, input_size, start_code);
		    /* Comment */
		    else if (start_code == COM)
			mjpeg_decode_com(s, s->buffer, input_size);
		}
#endif
            }
        }
 not_the_end:
	;
    }
 the_end:
    return buf_ptr - buf;
}

static int mjpeg_decode_end(AVCodecContext *avctx)
{
    MJpegDecodeContext *s = avctx->priv_data;
    int i, j;

    for(i=0;i<MAX_COMPONENTS;i++)
        av_free(s->current_picture[i]);
    for(i=0;i<2;i++) {
        for(j=0;j<4;j++)
            free_vlc(&s->vlcs[i][j]);
    }
    return 0;
}

AVCodec mjpeg_decoder = {
    "mjpeg",
    CODEC_TYPE_VIDEO,
    CODEC_ID_MJPEG,
    sizeof(MJpegDecodeContext),
    mjpeg_decode_init,
    NULL,
    mjpeg_decode_end,
    mjpeg_decode_frame,
    0,
    NULL
};