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

[liushuyu at aosc.io]

On 2020-09-03 14:17, Carl Eugen Hoyos wrote:
> 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.
> 
Will do. Should I also keep the else clause here?

>> +    } else {
>> +        avpriv_request_sample(s, "version %d", version);
>> +        return AVERROR_PATCHWELCOME;
>> +    }

> Carl Eugen
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Thanks for your review again!

Thanks,
Zixing