int ff_probe_input_buffer(ByteIOContext **pb, AVInputFormat **fmt,
                          const char *filename, void *logctx,
                          unsigned int offset, unsigned int max_probe_size)
{
    AVProbeData pd = { filename ? filename : "", NULL, -offset };
    unsigned char *buf = NULL;
    int probe_size;

    if (!max_probe_size) {
        max_probe_size = PROBE_BUF_MAX;
    } else if (max_probe_size > PROBE_BUF_MAX) {
        max_probe_size = PROBE_BUF_MAX;
    } else if (max_probe_size < PROBE_BUF_MIN) {
        return AVERROR(EINVAL);
    }

    if (offset >= max_probe_size) {
        return AVERROR(EINVAL);
    }

    for(probe_size= PROBE_BUF_MIN; probe_size<=max_probe_size && !*fmt; probe_size<<=1){
        int ret, score = probe_size < max_probe_size ? AVPROBE_SCORE_MAX/4 : 0;
        int buf_offset = (probe_size == PROBE_BUF_MIN) ? 0 : probe_size>>1;

        if (probe_size < offset) {
            continue;
        }

        /* read probe data */
        buf = av_realloc(buf, probe_size + AVPROBE_PADDING_SIZE);
        if ((ret = get_buffer(*pb, buf + buf_offset, probe_size - buf_offset)) < 0) {
            av_free(buf);
            return ret;
        }
        pd.buf_size += ret;
        pd.buf = &buf[offset];

        memset(pd.buf + pd.buf_size, 0, AVPROBE_PADDING_SIZE);

        /* guess file format */
        *fmt = av_probe_input_format2(&pd, 1, &score);
        if(*fmt){
            if(score <= AVPROBE_SCORE_MAX/4){ //this can only be true in the last iteration
                av_log(logctx, AV_LOG_WARNING, "Format detected only with low score of %d, misdetection possible!\n", score);
            }else
                av_log(logctx, AV_LOG_DEBUG, "Probed with size=%d and score=%d\n", probe_size, score);
        }
    }

    av_free(buf);
    if (url_fseek(*pb, 0, SEEK_SET) < 0) {
        url_fclose(*pb);
        if (url_fopen(pb, filename, URL_RDONLY) < 0)
            return AVERROR(EIO);
    }

    return 0;
}