int av_probe_input_buffer(AVIOContext *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 ret = 0, 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 = FFMIN(probe_size<<1, FFMAX(max_probe_size, probe_size+1))) {

        int score = probe_size < max_probe_size ? AVPROBE_SCORE_RETRY : 0;

        int buf_offset = (probe_size == PROBE_BUF_MIN) ? 0 : probe_size>>1;

        void *buftmp;



        if (probe_size < offset) {

            continue;

        }



        /* read probe data */

        buftmp = av_realloc(buf, probe_size + AVPROBE_PADDING_SIZE);

        if(!buftmp){

            av_free(buf);

            return AVERROR(ENOMEM);

        }

        buf=buftmp;

        if ((ret = avio_read(pb, buf + buf_offset, probe_size - buf_offset)) < 0) {

            /* fail if error was not end of file, otherwise, lower score */

            if (ret != AVERROR_EOF) {

                av_free(buf);

                return ret;

            }

            score = 0;

            ret = 0;            /* error was end of file, nothing read */

        }

        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_RETRY){ //this can only be true in the last iteration

                av_log(logctx, AV_LOG_WARNING, "Format %s detected only with low score of %d, misdetection possible!\n", (*fmt)->name, score);

            }else

                av_log(logctx, AV_LOG_DEBUG, "Format %s probed with size=%d and score=%d\n", (*fmt)->name, probe_size, score);

        }

    }



    if (!*fmt) {

        av_free(buf);

        return AVERROR_INVALIDDATA;

    }



    /* rewind. reuse probe buffer to avoid seeking */

    if ((ret = ffio_rewind_with_probe_data(pb, buf, pd.buf_size)) < 0)

        av_free(buf);



    return ret;

}
