static int wav_read_header(AVFormatContext *s)

{

    int64_t size, av_uninit(data_size);

    int64_t sample_count = 0;

    int rf64;

    uint32_t tag;

    AVIOContext *pb      = s->pb;

    AVStream *st         = NULL;

    WAVDemuxContext *wav = s->priv_data;

    int ret, got_fmt = 0;

    int64_t next_tag_ofs, data_ofs = -1;



    wav->unaligned = avio_tell(s->pb) & 1;



    wav->smv_data_ofs = -1;



    /* check RIFF header */

    tag = avio_rl32(pb);



    rf64 = tag == MKTAG('R', 'F', '6', '4');

    wav->rifx = tag == MKTAG('R', 'I', 'F', 'X');

    if (!rf64 && !wav->rifx && tag != MKTAG('R', 'I', 'F', 'F'))

        return AVERROR_INVALIDDATA;

    avio_rl32(pb); /* file size */

    tag = avio_rl32(pb);

    if (tag != MKTAG('W', 'A', 'V', 'E'))

        return AVERROR_INVALIDDATA;



    if (rf64) {

        if (avio_rl32(pb) != MKTAG('d', 's', '6', '4'))

            return AVERROR_INVALIDDATA;

        size = avio_rl32(pb);

        if (size < 24)

            return AVERROR_INVALIDDATA;

        avio_rl64(pb); /* RIFF size */



        data_size    = avio_rl64(pb);

        sample_count = avio_rl64(pb);



        if (data_size < 0 || sample_count < 0) {

            av_log(s, AV_LOG_ERROR, "negative data_size and/or sample_count in "

                   "ds64: data_size = %"PRId64", sample_count = %"PRId64"\n",

                   data_size, sample_count);

            return AVERROR_INVALIDDATA;

        }

        avio_skip(pb, size - 24); /* skip rest of ds64 chunk */



    }



    for (;;) {

        AVStream *vst;

        size         = next_tag(pb, &tag, wav->rifx);

        next_tag_ofs = avio_tell(pb) + size;



        if (avio_feof(pb))

            break;



        switch (tag) {

        case MKTAG('f', 'm', 't', ' '):

            /* only parse the first 'fmt ' tag found */

            if (!got_fmt && (ret = wav_parse_fmt_tag(s, size, &st)) < 0) {

                return ret;

            } else if (got_fmt)

                av_log(s, AV_LOG_WARNING, "found more than one 'fmt ' tag\n");



            got_fmt = 1;

            break;

        case MKTAG('d', 'a', 't', 'a'):

            if (!got_fmt) {

                av_log(s, AV_LOG_ERROR,

                       "found no 'fmt ' tag before the 'data' tag\n");

                return AVERROR_INVALIDDATA;

            }



            if (rf64) {

                next_tag_ofs = wav->data_end = avio_tell(pb) + data_size;

            } else {

                data_size    = size;

                next_tag_ofs = wav->data_end = size ? next_tag_ofs : INT64_MAX;

            }



            data_ofs = avio_tell(pb);



            /* don't look for footer metadata if we can't seek or if we don't

             * know where the data tag ends

             */

            if (!pb->seekable || (!rf64 && !size))

                goto break_loop;

            break;

        case MKTAG('f', 'a', 'c', 't'):

            if (!sample_count)

                sample_count = (!wav->rifx ? avio_rl32(pb) : avio_rb32(pb));

            break;

        case MKTAG('b', 'e', 'x', 't'):

            if ((ret = wav_parse_bext_tag(s, size)) < 0)

                return ret;

            break;

        case MKTAG('S','M','V','0'):

            if (!got_fmt) {

                av_log(s, AV_LOG_ERROR, "found no 'fmt ' tag before the 'SMV0' tag\n");

                return AVERROR_INVALIDDATA;

            }

            // SMV file, a wav file with video appended.

            if (size != MKTAG('0','2','0','0')) {

                av_log(s, AV_LOG_ERROR, "Unknown SMV version found\n");

                goto break_loop;

            }

            av_log(s, AV_LOG_DEBUG, "Found SMV data\n");

            wav->smv_given_first = 0;

            vst = avformat_new_stream(s, NULL);

            if (!vst)

                return AVERROR(ENOMEM);

            avio_r8(pb);

            vst->id = 1;

            vst->codec->codec_type = AVMEDIA_TYPE_VIDEO;

            vst->codec->codec_id = AV_CODEC_ID_SMVJPEG;

            vst->codec->width  = avio_rl24(pb);

            vst->codec->height = avio_rl24(pb);

            if (ff_alloc_extradata(vst->codec, 4)) {

                av_log(s, AV_LOG_ERROR, "Could not allocate extradata.\n");

                return AVERROR(ENOMEM);

            }

            size = avio_rl24(pb);

            wav->smv_data_ofs = avio_tell(pb) + (size - 5) * 3;

            avio_rl24(pb);

            wav->smv_block_size = avio_rl24(pb);

            avpriv_set_pts_info(vst, 32, 1, avio_rl24(pb));

            vst->duration = avio_rl24(pb);

            avio_rl24(pb);

            avio_rl24(pb);

            wav->smv_frames_per_jpeg = avio_rl24(pb);

            if (wav->smv_frames_per_jpeg > 65536) {

                av_log(s, AV_LOG_ERROR, "too many frames per jpeg\n");

                return AVERROR_INVALIDDATA;

            }

            AV_WL32(vst->codec->extradata, wav->smv_frames_per_jpeg);

            wav->smv_cur_pt = 0;

            goto break_loop;

        case MKTAG('L', 'I', 'S', 'T'):

            if (size < 4) {

                av_log(s, AV_LOG_ERROR, "too short LIST tag\n");

                return AVERROR_INVALIDDATA;

            }

            switch (avio_rl32(pb)) {

            case MKTAG('I', 'N', 'F', 'O'):

                ff_read_riff_info(s, size - 4);

            }

            break;

        }



        /* seek to next tag unless we know that we'll run into EOF */

        if ((avio_size(pb) > 0 && next_tag_ofs >= avio_size(pb)) ||

            wav_seek_tag(wav, pb, next_tag_ofs, SEEK_SET) < 0) {

            break;

        }

    }



break_loop:

    if (data_ofs < 0) {

        av_log(s, AV_LOG_ERROR, "no 'data' tag found\n");

        return AVERROR_INVALIDDATA;

    }



    avio_seek(pb, data_ofs, SEEK_SET);



    if (   data_size > 0 && sample_count && st->codec->channels

        && data_size / sample_count / st->codec->channels > 8) {

        av_log(s, AV_LOG_WARNING, "ignoring wrong sample_count %"PRId64"\n", sample_count);

        sample_count = 0;

    }



    if (!sample_count || av_get_exact_bits_per_sample(st->codec->codec_id) > 0)

        if (   st->codec->channels

            && data_size

            && av_get_bits_per_sample(st->codec->codec_id)

            && wav->data_end <= avio_size(pb))

            sample_count = (data_size << 3)

                                  /

                (st->codec->channels * (uint64_t)av_get_bits_per_sample(st->codec->codec_id));



    if (sample_count)

        st->duration = sample_count;



    ff_metadata_conv_ctx(s, NULL, wav_metadata_conv);

    ff_metadata_conv_ctx(s, NULL, ff_riff_info_conv);



    return 0;

}
