static int nist_read_header(AVFormatContext *s)
{
    char buffer[32], coding[32] = "pcm", format[32] = "01";
    int bps = 0, be = 0;
    int32_t header_size = -1;
    AVStream *st;

    st = avformat_new_stream(s, NULL);
    if (!st)
        return AVERROR(ENOMEM);

    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

    ff_get_line(s->pb, buffer, sizeof(buffer));
    ff_get_line(s->pb, buffer, sizeof(buffer));
    sscanf(buffer, "%"SCNd32, &header_size);
    if (header_size <= 0)
        return AVERROR_INVALIDDATA;

    while (!url_feof(s->pb)) {
        ff_get_line(s->pb, buffer, sizeof(buffer));

        if (avio_tell(s->pb) >= header_size)
            return AVERROR_INVALIDDATA;

        if (!memcmp(buffer, "end_head", 8)) {
            if (!st->codec->bits_per_coded_sample)
                st->codec->bits_per_coded_sample = bps << 3;

            if (!av_strcasecmp(coding, "pcm")) {
                st->codec->codec_id = ff_get_pcm_codec_id(st->codec->bits_per_coded_sample,
                                                          0, be, 0xFFFF);
            } else if (!av_strcasecmp(coding, "alaw")) {
                st->codec->codec_id = AV_CODEC_ID_PCM_ALAW;
            } else if (!av_strcasecmp(coding, "ulaw") ||
                       !av_strcasecmp(coding, "mu-law")) {
                st->codec->codec_id = AV_CODEC_ID_PCM_MULAW;
            } else {
                avpriv_request_sample(s, "coding %s", coding);
            }

            avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);

            st->codec->block_align = st->codec->bits_per_coded_sample * st->codec->channels / 8;

            if (avio_tell(s->pb) > header_size)
                return AVERROR_INVALIDDATA;

            avio_skip(s->pb, header_size - avio_tell(s->pb));

            return 0;
        } else if (!memcmp(buffer, "channel_count", 13)) {
            sscanf(buffer, "%*s %*s %"SCNd32, &st->codec->channels);
        } else if (!memcmp(buffer, "sample_byte_format", 18)) {
            sscanf(buffer, "%*s %*s %31s", format);

            if (!av_strcasecmp(format, "01")) {
                be = 0;
            } else if (!av_strcasecmp(format, "10")) {
                be = 1;
            } else if (av_strcasecmp(format, "1")) {
                avpriv_request_sample(s, "sample byte format %s", format);
                return AVERROR_PATCHWELCOME;
            }
        } else if (!memcmp(buffer, "sample_coding", 13)) {
            sscanf(buffer, "%*s %*s %31s", coding);
        } else if (!memcmp(buffer, "sample_count", 12)) {
            sscanf(buffer, "%*s %*s %"SCNd64, &st->duration);
        } else if (!memcmp(buffer, "sample_n_bytes", 14)) {
            sscanf(buffer, "%*s %*s %"SCNd32, &bps);
        } else if (!memcmp(buffer, "sample_rate", 11)) {
            sscanf(buffer, "%*s %*s %"SCNd32, &st->codec->sample_rate);
        } else if (!memcmp(buffer, "sample_sig_bits", 15)) {
            sscanf(buffer, "%*s %*s %"SCNd32, &st->codec->bits_per_coded_sample);
        } else {
            char key[32], value[32];
            if (sscanf(buffer, "%31s %*s %31s", key, value) == 3) {
                av_dict_set(&s->metadata, key, value, AV_DICT_APPEND);
            } else {
                av_log(s, AV_LOG_ERROR, "Failed to parse '%s' as metadata\n", buffer);
            }
        }
    }

    return AVERROR_EOF;
}