Re: license question

Hi,

I'll try to answer this, since I'm quite used to these questions by now.

> We produce a closed-source software based on Directshow, in which we
> (among many other things) decode video coming from external devices
> (cameras) for further image processing. As far as I can understand, if
> we use XViD to decode MPEG-4, but we dynamically build a directshow
> graph so that it selects "a" MPEG-4 decoder filter (which just happens
> to be XViD if this is the one installed), then this is considered as
> just using XViD and not as integration. In this case, we don't have to
> GPL our product.  If on the other hand we explicitely use the XViD
> filter in the graph, we have produced a derived product and we have to
> use GPL. Is this correct?

Usually, our policy is that if your software built in a way such that 
it can use any MPEG-4 decoder, i.e. it doesn't rely on XviD being 
installed or not, then it's not derivative works. If it fails to run
without XviD, or if the functionality is very limited, then it's 
derivative works. 

> Supposing that my analysis above is correct and we don't GPL our
> product, I have another question about distribution. 

In fact, all questions of "derivative works or not" are only about 
distribution. "At home" or "in the lab" you can create combinations
of XviD and anything else in any way you like. The question if this 
is derivative works or not only enters when you want to distribute 
publically, to a customer or something else. 

> We have an installable software, but also an out-of-the-box solution for
> the professional market, which consists of a PC with pre-installed OS
> and all necessary software. Suppose that we want to deliver the XViD
> filter pre-installed too. Would this be a problem? [...] 

Wow, this is a toughie... usually, our policy is that it isn't permitted
to create something that to the user looks like a single application 
out of XviD and a proprietary program, like an application that 
automatically installs XviD when it installs itself. 

Now, distribution by delivering a full PC, that case we really didn't
have, yet. I would rather tend to say, let's ignore the medium and say 
that if the program does not explicitely depend on XviD described above,
installing both an a PC and then delivering it to a customer is permitted
whereas if your program wouldn't work anymore after XviD had been removed, 
then it is not. 

But IANAL, either. What do you others on the list think? 


> PS: a small technical question as the cherry on the cake ;-) Do you have
> an idea of the DEcoding performance (fps depending on the resolution) of
> the codec? We're decoding multiple streams concurrently and so
> performance is quite an issue for us. Thanks!

You can't give absolute numbers on that, it depends very much on the 
material and other factors. Simply download it and try yourself. As you 
noted, usage is not limited. 
In relative terms, XviD is quite fast, faster than DivX, almost on 
par with FFmpeg by now, and HDX4 definitely is fastest. 
On my weak 1GHz C3 HTPC on Linux, I can decode a typical 640x272 at 60fps, 
including video display, or 100fps without display. 

gruel