[FFmpeg-devel] [PATCH]Auto-detection for concat demuxer

[Alexander Strasser]

Hi,

Nicolas George wrote:
> Le sextidi 16 pluviôse, an CCXXI, Michael Niedermayer a écrit :
> > we could have 2 demuxers
> > foobar and foobar-autoprobe
> > first would never autoprobe and second would enable safe mode
> 
> Yes, that would work, that is an interesting idea.
> 
> But is it worth it? It is quite hackish (and possibly brittle: it can hinder
> future evolutions of the probing system, or be broken by unrelated changes),
> and may prove confusing for the users (why are there two demuxers for the
> same format, why do they behave slightly differently?), for a benefit that
> appears to me very small.
> 
> If I had been less lazy and implemented file signature, filename checking
> and probing right from the start, this discussion would not have happened.
> 
> Also, I think that the current syntax, without the signature line, is too
> ambiguous: a completely unrelated file can easily look like a concat script.
> Also, maintaining the guessing-probing function for syntax extensions would
> require work, again for a benefit that I fail to see.
> 
> Last point, that I failed to notice until now: Carl's proposal only
> recognize when the "file" keyword is at the beginning of the line and
> followed by a space, while the demuxer accepts leading spaces and/or a tab
> afterwards. That is easy to fix, of course, but I believe it illustrates how
> this kind of probing is a maintenance burden.
> 
> I really think that having a fixed signature line and probing based only on
> it is the cleanest way.

  I have no strong opinion on this but I tend to agree with Nicolas.
IMHO as creative as all the solutions are to this point, don't they
have to little benefit and very probably potential (future) issues we
didn't think of yet?

  Also maybe I am missing something, but wouldn't it be easily possible
for people that do have older concat files to add the signature to those
existing files and have them properly auto-probed? (Assuming they do not
need to access unsafe locations.)

  Alexander