[vorbis-dev] Re: Ogg Spec, etc.

[Tor-Einar Jarnbjo]

Torsdag, 10 oktober 2002, skrev du:

>Actually, people have implemented perfectly valid Vorbis encoders and
>decoders before the specification was even published. I wouldn't 
go so far
>as to call other people on this list dirty liars, but I suspect 
that the
>spec that's published is good enough for them, and they're simply
>dealing with different issues than you are, and will not run into 
the same
>errors that you'll find in the spec.

The specification errors I reported 3-4 weeks ago include:

1. reading a wrong number of bits from the vorbis stream
2. accessing vector elements outside the actual vector size
3. calculation of data

Based on this, I still claim that it is not (or at least it was not 
until four weeks ago) possible to implement a working decoder or 
encoder based on the specification. The errors I've found and reported,
which are not yet corrected are all as far as I can see calculation 
mismatches, and will not make the decoder loose sync in the bitstream 
or segfault (as the two first errors certainly would do), but will 
just make the decoder introduce distortion in the decoded PCM data.

<p>If people have been able to implement other decoders than libvorbis,
they must certainly be based on either knowledge about the file 
format, which is not available in written form, or on the libvorbis 
source code. The first possibility is not available to me and I was 
hoping to be able to implement the decoder I am working on from scratch,
without having to use the libvorbis source code as a base.

>If you're having that problem, I'm sorry, but it looks like the only
>solution is to just keep working on it. When you find things that don't
>work, send them to Monty, and he'll do his best to make corrections 
when
>they're necessary and he has the time. We want to make the spec 
the best
>it can possibly be, and your help is certainly appreciated.

I've addressed several things and asked quite a few questions the 
last month on this list, and based on the response I've gotten until 
now, it certainly did not seem as if my help was appreciated :-/

<p>Tor

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