[NUT-devel] Fourcc spec

[Oded Shimon]

On Sat, Dec 23, 2006 at 09:13:59PM +0000, M?ns Rullg?rd wrote:
> Oded Shimon <ods15 at ods15.dyndns.org> writes:
> 
> > On Sat, Dec 23, 2006 at 03:09:24PM +0200, Oded Shimon wrote:
> >> On Sat, Dec 23, 2006 at 01:56:29PM +0100, Michael Niedermayer wrote:
> >> > if the lists are not normative that i bet every commercial company will
> >> > use their own fourcc divx, 3ivx, ...
> >> > why?
> >> > 1. the company can better claim that its their own supperior technology
> >> > 2. they dont need to bother to implement the standard correctly, its enough
> >> >    if their decoder matches their encoder, this is what has happened with
> >> >    codecs in avi and as its less work = less money it will happen again.
> >> >    It didnt happen with mpeg-ps/ts just because there are too many hw
> >> >    decoders around which cant be updated that easily all IMHO
> >> > 
> >> > if my hypothesis turns out to be true then 3. would loose the 
> >> > "single fourcc per codec" and ""Sane" codec names" as in practice the
> >> > majority of videos would not use the recommanded fourccs
> >> > 
> >> > so that brings us to option 4 which would require a player to only support
> >> > a codec if the one and only standard fourcc where used, if a unknown fourcc
> >> > is used demuxing it would be a violation of the spec ...
> >> > 
> >> > if that would prevent the issue iam not sure though ...
> >> 
> >> The list IS normative for demuxers, not for muxers. This was already in my 
> >> original proposal, I forgot to re-mention it here.
> >
> > To spell it out again:
> >
> > A muxer SHOULD use the fourcc from the codec list
> > A demuxer MUST support the fourcc from the codec list if it supports the 
> > codec at all
> >
> > Which means demuxers can have additional fourcc's to the ones in the 
> > official list, and a muxer can do whatever it wants. But obviously, both 
> > are better off using the official list.
> 
> This makes no sense at all, but I think you already knew my opinion...

Actually, no, I'm confused by your reply...
I was slightly off - the demuxer is better off using as many fourcc's as 
it wants, but it MUST include also the official list. The muxer, in most 
cases, is better off using only fourcc's from the official list, so it has 
garuntee of demuxers supporting it. I fail to see how this does not make 
sense. I don't know if you noticed, but I'm going through this entire 
thing only because of you, I personally do not care. So please, present 
your arguments.

In the case of a company _intentionally_ not using an official fourcc, 
then I don't really care, because if they are doing it intentionally they 
will always do it regardless of what we ask. (Even if we say MPEG-4 ASP 
MUST have this fourcc, they can claim their codec is something 
else/superior and has another fourcc)

- ods15