[vlc-devel] [PATCH] stream_filter: add ADF stream filter (Fixes #17501)

[Francois Cartegnie]

Le 25/10/2016 à 17:31, Filip Roséen a écrit :
> Hi Francois,
> 
> On 2016-10-25 17:18, Francois Cartegnie wrote:
> 
>> Le 25/10/2016 à 06:56, Tristan Matthews a écrit :
>>> +    /* Probe for XOR'd ID3 tag. */
>>> +    if( memcmp( peek, "\x6B\x66\x11", 3 ) )
>>> +        return VLC_EGENERIC;
>>
>> Being before any demuxer and packetizer,
>> expect high rate of false positives.
> 
>  - Why would this cause a *"high rate of false positives"?
> 
> It is equivalent to a *demuxer* probing for the same data, and as far
> as I could see when I looked up the *magic-bytes* used, there is no
> *file-format* that is publically documented that uses that marker.

Probing a single sequence is *weak*.
and data has no alignment guarantee.

Hence the demuxers priorities and the packetizer based demuxers and
multiple frames probing for most audio codecs. (and libav has even more
intensive probing)

Putting this as stream filter gives it higher priority than any demuxer.

Will break any non aligned, sync code based, if the stream starts with
"\x6B\x66\x11" (raw video, raw audio, ts, ps...), where demux with low
score would not.

Francois