[NUT-devel] Fourcc spec

[Rich Felker]

On Sun, Dec 24, 2006 at 01:21:00PM +0100, Michael Niedermayer wrote:
> > > 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.
> > 
> > Having a list makes no sense unless it's normative for both sides.
> 
> agree though thats a statement and not a argument
> the argument ("proof" by contradction) is that if the muxer can choose any
> fourcc for standard mpeg4 (not buggy near mpeg4 ...) then a demuxer cannot
> support mpeg4 in nut with 100% certainity, theres the very small possibility
> that mpeg4 would be stored with another new and unknown fourcc ...
> 
> 
> btw, one interresting goal of the codec id system should be:
> the system must be generic so that
> 2 users who otherwise cannot communicate can mux and demux a codec X in nut
> with high propability of success, without manual intervention and assuming
> the codec has a de-facto standard fourcc in avi

agree. some thoughts...

- we cannot stop people from inventing their own nonstandard id's for
  their bad implementations of (mostly) standard codecs, regardless of
  what id system we use.

- aside from such malicious parties, people making nut files will
  generally be interested in having their files be playable on as many
  players as possible.

- if we provide a list of officially sanctioned codec id's for
  standard codecs, and require any conformant player to support these
  id's if it supports the codec in question at all, then (1) we can
  officially flame anyone making a player that omits support for the
  standard name, and (2) people intending for their files to be widely
  playable will use the standard name since other names might not be
  supported by settop devices, etc.

- players wanting to provide maximum compatibility will also support
  various broken names for codecs, but this provides no significant
  implementation difficulty in complexity, size, or performance.

it's for these reasons that i want to stick with what oded has been
saying. the only question in my mind is _which_ names should we agree
upon as the standard ones????

rich