[asterisk-users] FXO Cards - T38

[Steve Underwood]

Rob Hillis wrote:
> T.38 is for all intents and purposes a codec.  It's purpose is to 
> re-encode a fax transmission as a data stream to be re-assembled at 
> the other end as if it were a fax call.  Seems to me to be pretty 
> close to the definition of a codec to me.
T.38 is not a simple re-encoder. It cannot work on a single stream, 
independent of the related stream going in the opposite direction. This 
is not what most people think of as a codec, and it doesn't fit into the 
way codecs are handled in most platforms. This includes Asterisk, where 
the two directions of codec processing are independent pipes.
> Your original comment was that you cannot use T.38 and G.729 in 
> Asterisk at the same time.  On a technical level, this is /not/ true, 
> especially if the T.38 implementation does not rely on SpanDSP. 
> (whether or not such an implementation exists is another question)  
> Breaking license conditions is a separate issue altogether.
I was talking about the T.38 support which has been added to Asterisk 
add-ons.
> You also appear to have answered another one of your questions on this 
> forum to someone else ("why on earth would you want to remove SpanDSP 
> as a dependency?") by telling us that you can't run G.729 at the same 
> time as T.38.
Again, this was with reference to the code which has been added to 
Asterisk add-ons.
> I'm also curious as to why you assert that using G.729 in Asterisk 
> (/not/ ABE) at the same time as a T.38 implementation that relies on 
> SpanDSP since these are two completely separate plugins that are 
> installed and acquired separately.  That's almost like asserting that 
> you can't run any commercial X application if you've installed my XYZ 
> web browser on the same machine.  Just because they use a common 
> software base (X in this instance) /doesn't/ mean that you're 
> violating the GPL by running non commercial software on the same machine.
Try reading the GPL and the FSF's interpretation of it. If things are 
running in the same address space as my code, they need to be GPL 
compatible, or I am likely to take action. We have tackled this issue in 
other ways, taking non-GPL code outside the address space of GPL code. 
This can work well for things like G.729, as the compute in the codec is 
so great it swamps the process to process communications overhead. It 
creates a greater problem for things like ucLinux platforms (e.g. 
Blackfin), as everything on the entire machine is in the same address 
space.
>
> A more meaningful interpretation of the GPL would be that you either 
> can or can't run a T.38 implementation with Asterisk /full stop/.  
> Either the license is compatible, or it isn't.  Trying to force any 
> other interpretation on people will end up with you being dismissed as 
> an extremist.
An extremist is someone who thinks they can do as they please, without 
regard to the legitimate rights of others. In this case it appears to be 
an accurate description of you.

I write code. I let people use it. I set reasonable, and widely 
established rules for its use. I expect people to stick to them. I never 
ask anyone to use my stuff. If you don't like my rules, Attractel 
provides an alternative T.38 implementation, which is fully licence 
compatible with Asterisk ABE and proprietary codecs.

Regards,
Steve