[FFmpeg-devel] [PATCH v3] avformat: add mca demuxer

[Carl Eugen Hoyos]

Am Do., 3. Sept. 2020 um 01:17 Uhr schrieb <liushuyu at aosc.io>:

> +static int probe(const AVProbeData *p)
> +{
> +    if (AV_RL32(p->buf) == MKTAG('M', 'A', 'D', 'P') &&
> +        AV_RL16(p->buf + 4) <= 0xff)
> +        return AVPROBE_SCORE_MAX / 3 * 2;
> +    return 0;
> +}

> +    if (version <= 4) {
> +        // version <= 4 needs to use the file size to calculate the offsets
> +        if (file_size < 0) {
> +            return AVERROR(EIO);
> +        }
> +        if (file_size - data_size > UINT32_MAX)
> +            return AVERROR_INVALIDDATA;
> +        m->data_start = file_size - data_size;
> +        if (version <= 3) {
> +            nb_metadata = 0;
> +            // header_size is not available or incorrect in older versions
> +            header_size = m->data_start;
> +        }
> +    } else if (version == 5) {
> +        // read data_start location from the header
> +        if (0x30 * par->channels + 0x4 > header_size)
> +            return AVERROR_INVALIDDATA;
> +        data_offset = header_size - 0x30 * par->channels - 0x4;
> +        if ((ret_size = avio_seek(s->pb, data_offset, SEEK_SET)) < 0)
> +            return ret_size;
> +        m->data_start = avio_rl32(s->pb);
> +        // check if the metadata is reasonable
> +        if (file_size > 0 && (int64_t)m->data_start + data_size > file_size) {
> +            // the header is broken beyond repair
> +            if ((int64_t)header_size + data_size > file_size) {
> +                av_log(s, AV_LOG_ERROR,
> +                       "MCA metadata corrupted, unable to determine the data offset.\n");
> +                return AVERROR_INVALIDDATA;
> +            }
> +            // recover the data_start information from the data size
> +            av_log(s, AV_LOG_WARNING,
> +                   "Incorrect header size found in metadata, "
> +                   "header size approximated from the data size\n");
> +            if (file_size - data_offset > UINT32_MAX)
> +                return AVERROR_INVALIDDATA;
> +            m->data_start = file_size - data_size;
> +        }
> +    } else {
> +        avpriv_request_sample(s, "version %d", version);
> +        return AVERROR_PATCHWELCOME;
> +    }

It seems to me that you are much stricter checking the version
when reading the header information than when probing the file
but if there is a difference, the probing should be stricter.

Please check in the probe function if version <= 5.

Carl Eugen