st->need_parsing = 2;
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;    unsigned int size, nb_frames;    int i, n;    AVStream *st;    AVIStream *ast;    int xan_video = 0;  /* hack to support Xan A/V */    avi->stream_index= -1;        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;                if(size) avi->movi_end = avi->movi_list + size;                else     avi->movi_end = url_fsize(pb);#ifdef DEBUG                printf("movi end=%Lx\n", avi->movi_end);#endif                goto end_of_header;            }            break;        case MKTAG('d', 'm', 'l', 'h'):	    avi->is_odml = 1;	    url_fskip(pb, size + (size & 1));	    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 */#ifdef DEBUG        print_tag("strh", tag1, -1);#endif            if(tag1 == MKTAG('i', 'a', 'v', 's') || tag1 == 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;                		ast = s->streams[0]->priv_data;		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;		s->streams[0]->priv_data = ast;		url_fskip(pb, 3 * 4);		ast->scale = get_le32(pb);		ast->rate = get_le32(pb);	        stream_index = s->nb_streams - 1;		url_fskip(pb, size - 7*4);                break;            }            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); /* initial frame */            ast->scale = get_le32(pb);            ast->rate = get_le32(pb);            if(ast->scale && ast->rate){            }else if(frame_period){                ast->rate = 1000000;                ast->scale = frame_period;            }else{                ast->rate = 25;                ast->scale = 1;            }            av_set_pts_info(st, 64, ast->scale, ast->rate);                                ast->start= get_le32(pb); /* start */            nb_frames = get_le32(pb);            st->start_time = 0;            st->duration = nb_frames;            get_le32(pb); /* buffer size */            get_le32(pb); /* quality */            ast->sample_size = get_le32(pb); /* sample ssize *///            av_log(NULL, AV_LOG_DEBUG, "%d %d %d %d\n", ast->rate, ast->scale, ast->start, ast->sample_size);            switch(tag1) {	    case MKTAG('v', 'i', 'd', 's'):                codec_type = CODEC_TYPE_VIDEO;                ast->sample_size = 0;                break;            case MKTAG('a', 'u', 'd', 's'):                codec_type = CODEC_TYPE_AUDIO;                break;            case MKTAG('t', 'x', 't', 's'):                //FIXME                 codec_type = CODEC_TYPE_DATA; //CODEC_TYPE_SUB ?  FIXME                break;            case MKTAG('p', 'a', 'd', 's'):                codec_type = CODEC_TYPE_UNKNOWN;                stream_index--;                break;            default:                av_log(s, AV_LOG_ERROR, "unknown stream type %X\n", tag1);                goto fail;            }            url_fskip(pb, size - 12 * 4);            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 */                 if(size > 10*4 && size<(1<<30)){                    st->codec->extradata_size= size - 10*4;                    st->codec->extradata= av_malloc(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_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:                    st->codec->codec_type = CODEC_TYPE_DATA;                    st->codec->codec_id= CODEC_ID_NONE;                    st->codec->codec_tag= 0;                    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;    }    assert(!avi->index_loaded);    avi_load_index(s);    avi->index_loaded = 1;     return 0;}