[PD] GEM : GLSL Mixer - working 2 channel video mixer example

cyrille henry cyrille.henry at la-kitchen.fr
Tue Dec 25 23:56:43 CET 2007

vade a écrit :
> Hm. Interesting. GEM does not have a drop frame system?
i don't fell it would be very usefull.
that would create more problem that what it could solve.

of course, nothing should crash, just slow down the system.

> Im not sure  
> about the scheduler differences between PD and Max/Jitter, but most  
> Jitter events are in a different queue and have a drop frame handling  
> method built in to each object, and when drawing with openGL one  
> should use a 'qmetro', or a queue limited metro -  to avoid such a  
> case. Im speaking a bit out of my realm of expertise but I dont really  
> think a Patcher should be able to do that, if it did indeed lock up  
> your system.

i think gem sheduling is just like using a metro with jitter.
(but no qmetro)


> What is the proper way of handing this in PD/GEM? Sorry for causing a  
> crash. I saw your PD Jitter patch, but frankly I think some drop frame  
> system should be built into GEM to handle this automatically.
> Anyway, what kind of powerbook? It may not have the required hardware  
> support for the shader, which might be why you are only getting 10fps,  
> via software fallback?
> On Dec 25, 2007, at 1:04 PM, Max Neupert wrote:
>> very interesting, but also a good example on how to lock the computer
>> completely with gem - at least my old powerbook. i had to hard reset
>> because complete unresponsiveness. with [frame 10( it runs nicely
>> though. see my last post on how to avoid the lock-up.
>> max
>> Am 24.12.2007 um 21:35 schrieb vade:
>>> Yes, very efficient, and also give you LOTS of flexibility . the
>>> regular GL_BLEND_MODES do not offer that many variations (not many  
>>> are
>>> useful for video). Want to make a GPU powered chroma key - shader.
>>> Want to make feedback but have FSAA on, probably shader :)
>>> etc etc. Want to make 4 way mixer? shader! See where I am going
>>> here? :)
>>> On Dec 24, 2007, at 3:29 PM, Hans-Christoph Steiner wrote:
>>>> Nice, works for me.  Is the idea that shaders are a efficient way of
>>>> mixing video?
>>>> .hc
>>>> On Dec 24, 2007, at 12:04 PM, vade wrote:
>>>>> Hello
>>>>> Here is a 2 channel mixer using overlay blend mode with GLSL. This
>>>>> works, is decently fast and gives me the expected result.
>>>>> If you want more blend modes, feel free to grab them from http://
>>>>> 001.vade.info
>>>>> (or elsewhere, most are trivial to figure out)- the glsl shaders
>>>>> for the mixers use the same subroutine layout in the glsl, so it is
>>>>> trivial to swap. I did not include them out of sheer laziness.
>>>>> Caveats with PD 0.4.03 Extended nightly from Dec 24th (Mac OS X
>>>>> 10.5.1, QT 7.3, Intel):
>>>>> - had to edit the GLSL program to fix multitexture coordinate
>>>>> issue. Only can use the texture dims from the zeroths texture unit.
>>>>> - could not get sampler2DRect working at all - only had a single
>>>>> texel mapped it seemed.
>>>>> - had weird issue where I would sometimes have to close the gemwin
>>>>> (0, destroy) and then re create it to see the textures assigned to
>>>>> texture units.
>>>>> 	this happened most often after closing and re-opening the patch.
>>>>> Please see the included question(s) within the PD patch concerning
>>>>> using framebuffer to grab the output of the rendered shader and
>>>>> send it to yet another shader. Ive included an exposure shader in
>>>>> an attempt to make a chain of GLSL effects. I however could not get
>>>>> gemframebuffer to output any usable texture after using  
>>>>> glslprogram.
>>>>> Thanks, hope this is helpful to those out there
>>>>> FUDDLE DUDDLE !@#!@#!@#()*!@#(*@#
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