[ogg-dev] OggPCM proposal feedback

Erik de Castro Lopo mle+xiph at mega-nerd.com
Fri Nov 11 00:17:53 PST 2005

Arc wrote:

> Ok so we cap it to 64bit, since much more than that doesn't make sense (96bit 
> would be a "long double" C type)

On x86 CPUs, "long double" is 80 bits.

> I really don't like this idea, but I will entertain, formatting it as follows:
> ID  Type  Bits  
> 0   Int   8
> 1   uInt  8
> 2   Int   16
> 3   Int   24
> 4   Int   32
> 5   Float 32
> 6   Float 64
> 7   Extended - Unsupported by any v1.0 software
> This is what I consider a compromise, an additional minor revision can be made 
> to add an additional set of types not covered by this layout while not loosing 
> compatability with these types.
> I added this to the wiki, to look at.  It requires 3 bits to encode, which when 
> combined with the MSB/LSB flag bit, leaves a nibble for extended types or 
> channel association. 

We're talking about a file header here. Even if the header is a kilobyte in
size, it will be completely **dwarfed** by the audio data following. So why 
are you counting single bits like this?

I have suggested something better. A number of people have agreed with my
suggestion. As yet, noone has stepped forward to support your proposal.
Why is that?

> Now - channel association/scheme, or whatever a more appropriate name would be.. 
> this has got to be a lookup table, too.  I'm thinking:
>  0 Mono
>  1 Stereo
>  2 Quadraphonic
>  3 Ambisonic
>  4 Dolby 5.1
>  5 Dolby 6.1 (used in Dolby Digital EX)
>  6 Dolby 7.1
>  7 Extended
> This is 3 bits, leaving one bit free for an extra flag, if needed, for one other 
> bit of configuration which may be needed.  We could also extend this to 4 bits, 
> leaving many of them "Extended" for future minor versions.

Until yesterday, you were not even aware of this issue and now you think you
know enough to design something that implements it? Thats nuts! Your chances
of getting it wrong are close to 100%.

  Erik de Castro Lopo
"Men never do evil so completely and cheerfully as when they do it
from religious conviction."  -- Blaise Pascal, mathematician, 1670

More information about the ogg-dev mailing list