get_le32(pb);
ast->start= get_le32(pb);
static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap){    AVIContext *avi = s->priv_data;    ByteIOContext *pb = &s->pb;    uint32_t tag, tag1, handler;    int codec_type, stream_index, frame_period, bit_rate, scale, rate;    unsigned int size, nb_frames;    int i, n;    AVStream *st;    AVIStream *ast;    int xan_video = 0;  /* hack to support Xan A/V */    av_set_pts_info(s, 64, 1, AV_TIME_BASE);    if (get_riff(avi, pb) < 0)        return -1;    /* first list tag */    stream_index = -1;    codec_type = -1;    frame_period = 0;    for(;;) {        if (url_feof(pb))            goto fail;        tag = get_le32(pb);        size = get_le32(pb);#ifdef DEBUG        print_tag("tag", tag, size);#endif        switch(tag) {        case MKTAG('L', 'I', 'S', 'T'):            /* ignored, except when start of video packets */            tag1 = get_le32(pb);#ifdef DEBUG            print_tag("list", tag1, 0);#endif            if (tag1 == MKTAG('m', 'o', 'v', 'i')) {                avi->movi_list = url_ftell(pb) - 4;                avi->movi_end = avi->movi_list + size;#ifdef DEBUG                printf("movi end=%Lx\n", avi->movi_end);#endif                goto end_of_header;            }            break;        case MKTAG('a', 'v', 'i', 'h'):	    /* avi header */            /* using frame_period is bad idea */            frame_period = get_le32(pb);            bit_rate = get_le32(pb) * 8;	    url_fskip(pb, 4 * 4);            n = get_le32(pb);            for(i=0;i<n;i++) {                AVIStream *ast;                st = av_new_stream(s, i);                if (!st)                    goto fail;                ast = av_mallocz(sizeof(AVIStream));                if (!ast)                    goto fail;                st->priv_data = ast;	    }            url_fskip(pb, size - 7 * 4);            break;        case MKTAG('s', 't', 'r', 'h'):            /* stream header */            stream_index++;            tag1 = get_le32(pb);            handler = get_le32(pb); /* codec tag */            switch(tag1) {            case MKTAG('i', 'a', 'v', 's'):	    case MKTAG('i', 'v', 'a', 's'):                /* 	         * After some consideration -- I don't think we 	         * have to support anything but DV in a type1 AVIs.	         */	        if (s->nb_streams != 1)		    goto fail;	        		if (handler != MKTAG('d', 'v', 's', 'd') &&	            handler != MKTAG('d', 'v', 'h', 'd') &&		    handler != MKTAG('d', 'v', 's', 'l'))	           goto fail;                		av_freep(&s->streams[0]->codec.extradata);		av_freep(&s->streams[0]);		s->nb_streams = 0;	        avi->dv_demux = dv_init_demux(s);		if (!avi->dv_demux)		    goto fail;	        stream_index = s->nb_streams - 1;		url_fskip(pb, size - 8);		break;	    case MKTAG('v', 'i', 'd', 's'):                codec_type = CODEC_TYPE_VIDEO;                if (stream_index >= s->nb_streams) {                    url_fskip(pb, size - 8);                    break;                }                 st = s->streams[stream_index];                ast = st->priv_data;                st->codec.stream_codec_tag= handler;                                get_le32(pb); /* flags */                get_le16(pb); /* priority */                get_le16(pb); /* language */                get_le32(pb); /* XXX: initial frame ? */                scale = get_le32(pb); /* scale */                rate = get_le32(pb); /* rate */                if(scale && rate){                }else if(frame_period){                    rate = 1000000;                    scale = frame_period;                }else{                    rate = 25;                    scale = 1;                }                ast->rate = rate;                ast->scale = scale;                st->codec.frame_rate = rate;                st->codec.frame_rate_base = scale;                get_le32(pb); /* start */                nb_frames = get_le32(pb);                st->start_time = 0;                st->duration = (double)nb_frames *                     st->codec.frame_rate_base * AV_TIME_BASE /                     st->codec.frame_rate;		url_fskip(pb, size - 9 * 4);                break;            case MKTAG('a', 'u', 'd', 's'):                {                    unsigned int length;                    codec_type = CODEC_TYPE_AUDIO;                    if (stream_index >= s->nb_streams) {                        url_fskip(pb, size - 8);                        break;                    }                     st = s->streams[stream_index];                    ast = st->priv_data;                                        get_le32(pb); /* flags */                    get_le16(pb); /* priority */                    get_le16(pb); /* language */                    get_le32(pb); /* initial frame */                    ast->scale = get_le32(pb); /* scale */                    ast->rate = get_le32(pb);                    get_le32(pb); /* start */                    length = get_le32(pb); /* length, in samples or bytes */                    get_le32(pb); /* buffer size */                    get_le32(pb); /* quality */                    ast->sample_size = get_le32(pb); /* sample ssize */                    st->start_time = 0;                    if (ast->rate != 0)                        st->duration = (int64_t)length * AV_TIME_BASE / ast->rate;                    url_fskip(pb, size - 12 * 4);                }                break;            default:                goto fail;            }            break;        case MKTAG('s', 't', 'r', 'f'):            /* stream header */            if (stream_index >= s->nb_streams || avi->dv_demux) {                url_fskip(pb, size);            } else {                st = s->streams[stream_index];                switch(codec_type) {                case CODEC_TYPE_VIDEO:                    get_le32(pb); /* size */                    st->codec.width = get_le32(pb);                    st->codec.height = get_le32(pb);                    get_le16(pb); /* panes */                    st->codec.bits_per_sample= get_le16(pb); /* depth */                    tag1 = get_le32(pb);                    get_le32(pb); /* ImageSize */                    get_le32(pb); /* XPelsPerMeter */                    get_le32(pb); /* YPelsPerMeter */                    get_le32(pb); /* ClrUsed */                    get_le32(pb); /* ClrImportant */                    st->codec.extradata_size= size - 10*4;                    st->codec.extradata= av_malloc(st->codec.extradata_size);                    get_buffer(pb, st->codec.extradata, st->codec.extradata_size);                                        if(st->codec.extradata_size & 1) //FIXME check if the encoder really did this correctly                        get_byte(pb);                    /* Extract palette from extradata if bpp <= 8 */                    /* This code assumes that extradata contains only palette */                    /* This is true for all paletted codecs implemented in ffmpeg */                    if (st->codec.extradata_size && (st->codec.bits_per_sample <= 8)) {                        st->codec.palctrl = av_mallocz(sizeof(AVPaletteControl));#ifdef WORDS_BIGENDIAN                        for (i = 0; i < FFMIN(st->codec.extradata_size, AVPALETTE_SIZE)/4; i++)                            st->codec.palctrl->palette[i] = bswap_32(((uint32_t*)st->codec.extradata)[i]);#else                        memcpy(st->codec.palctrl->palette, st->codec.extradata,                               FFMIN(st->codec.extradata_size, AVPALETTE_SIZE));#endif                        st->codec.palctrl->palette_changed = 1;                    }#ifdef DEBUG                    print_tag("video", tag1, 0);#endif                    st->codec.codec_type = CODEC_TYPE_VIDEO;                    st->codec.codec_tag = tag1;                    st->codec.codec_id = codec_get_id(codec_bmp_tags, tag1);                    if (st->codec.codec_id == CODEC_ID_XAN_WC4)                        xan_video = 1;//                    url_fskip(pb, size - 5 * 4);                    break;                case CODEC_TYPE_AUDIO:                    get_wav_header(pb, &st->codec, size);                    if (size%2) /* 2-aligned (fix for Stargate SG-1 - 3x18 - Shades of Grey.avi) */                        url_fskip(pb, 1);                    /* special case time: To support Xan DPCM, hardcode                     * the format if Xxan is the video codec */                    st->need_parsing = 1;                    /* force parsing as several audio frames can be in                       one packet */                    if (xan_video)                        st->codec.codec_id = CODEC_ID_XAN_DPCM;                    break;                default:                    url_fskip(pb, size);                    break;                }            }            break;        default:            /* skip tag */            size += (size & 1);            url_fskip(pb, size);            break;        }    } end_of_header:    /* check stream number */    if (stream_index != s->nb_streams - 1) {    fail:        for(i=0;i<s->nb_streams;i++) {            av_freep(&s->streams[i]->codec.extradata);            av_freep(&s->streams[i]);        }        return -1;    }    return 0;}