[gst-devel] Hello and my 1st question

Thomas Vander Stichele thomas at urgent.rug.ac.be
Thu Apr 25 02:55:08 CEST 2002

Hi Kentarou,

> Some days ago, Thomas Vander Stichle invited me to GStreamer development,
> and today I saw an impact news on GStreamer web page. Fantastic! Great!
> (oh my poor English...)

I'm glad you like it ! Wim Taymans (wtay) coded them pretty quickly, and 
they work perfectly.  We're currently thinking about how to go about for 
the other plugins.

> Okay, let me talk about my future plan. First of all, we, EffecTV developers,
> do not change its core architecture to GStreamer. Please, please wait until
> my talk is finished. We want to keep EffecTV as an "easy to use/launch" application,
> because we consider our product as an "toy application" (of course, ahem, we
> believe that EffecTV is a great-novel-fantastic-and-so-on toy:).
> For this sake, we would like to keep it simple and monolithic-like application.

I have given this some thought since I would expect you want to keep it 
like this.

I think it would be fairly easy to build, from your current source tree, 
both your simple monolithic app, AND a shared library that can be used by 
anyone, from the same code base.

Basically, all that is required is some autoconf/automake things, and an 
extraction of the actual filter algorithms.  These get put in a different
source code file, each algorithm in it's function.

This function can then be called from your ...Draw function, but it can 
also be put in the shared lib.  I think this is the easiest way to do this 
and from this we can both win.  It requires relatively little work and 
would also help your project in providing better code abstraction.  It's 
just my current idea, of course you are welcome to reject it ;)
In any case, I will try to do what I just said for one plugin to see if 
it's easy to do, workable, and efficient enough for both effecTV and 

> On the other hand, I am planning to start new branch, say "EffecTV+",
> as the next generation of EffecTV. EffecTV+ is based on GStreamer.
> It is more flexible, and for experienced user who need more powerful effect.
> It is provided as a set of GStreamer plugin.

That is a good idea as well, so this might be the better option - I'm just 
not sure at this moment ;) The easiest way would be for you to code up a 
good shared library with an easy API - which we can work out together - 
together with just one plugin in GStreamer depending on the lib, in such a 
way that the plugin can be extended just by upgrading the EffecTV+ 
library.  This is probably something we can work out together.

> And now, my 1st question.
> Does the effect plugin can receive multiple video streams? I want to create
> A/B roll effect. As you know, one of the most important effect VJs requires
> is A/B roll for scene changing. According to my survey, there are few effort
> to create novel A/B roll effect.

Not at this point, but it is really easy to do so.  GStreamer elements 
can have as many source or sink pads as you want.  For an example of this 
in the audio domain, look at adder, which mixes zero, one, two or more 
audio incoming streams.  The harder bits are probably working out how to 
deal with varying incoming buffer sizes (as I had to work out with adder), 
but adder has a pretty easy and efficient algorithm for that.

In any case, feel free to post questions to the list.  I am not a video 
person, but I'm excited that you want to work with us, because your 
effects are really good ;)



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