[PD-dev] sound + video : real time issues

[Ricardo Fabbri]

Thanks for the replies.

problems solved by using 2 Pd instances, one for video, the other for
audio, communicating via OSC on the same machine (or even different
machines). The machine also had to have a better CPU as doing this on a
slower dualcore laptop only fixed the audio, while the video got very slow.

best,

On Monday, November 14, 2011, Hans-Christoph Steiner <hans at at.or.at> wrote:
>
> I think generally, for gem + audio patches, people run two instances of
Pd, one for Gem and the other for the audio.  The audio instance has
realtime priority, and the Gem one does not.
>
> .hc
>
> On Nov 13, 2011, at 10:17 PM, Ricardo Fabbri wrote:
>
>> Hi,
>>
>> I am building instalations/instruments which control sounds
>> through the webcam, using a color detector that I submitted to this
>> list a couple of days ago. Things work well, and I am just facing real
>> time/delay issues now.
>> When I try to generate sound with any pix
>> processing, I am getting jumps in the sound (like on/off sounds at
>> about 5-20Hz). Turning off any pix processing, the sound is then back
>> to normal, even if I show the raw video from the camera on a gemwin.
>> By pix processing I mean anything with even only 1 pass through the
>> image on the CPU. I am using a ps3eye camera, which makes things
>> better as it has a high framerate, but I still get interruptions in
>> the sound.
>>
>> Why is this lag in the sound? The image with the output of the pix
>> processing doesn't seem to be moving any slower with or without sound.
>>
>> What are your experiences in trying to get gem pix processing, video,
>> and DSP to work in real time? My application is interactive, so that I
>> really need the sound to be as smooth as possible. Here are some
>> factors I will investigate, let me know if they make any sense to you:
>>
>> - It could be just too much data, even a single pass on each pixel
>> could be causing delays/jumps. I could downsample the image prior to
>> any pix processing
>> - The kernel is too slow in processing the video stream; I tried '-rt'
>> with no success
>> - Perhaps there is a problem in Pd sound scheduling vs pix processing
>> - Perhaps its just the CPU. In fact, I used OSC to do the video on one
>> machine, send the parameters to a second machine which then processes
>> the audio there. This effectively solved the problem. Question is, is
>> this due to CPU or to another factor?
>>
>> I would really appreciate hearing ideas from you, as I am new to this.
>> Best,
>> Ricardo Fabbri
>> --
>> Linux registered user #175401
>> www.lems.brown.edu/~rfabbri
>> labmacambira.sf.net
>>
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>
>
>
>
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>
> Computer science is no more related to the computer than astronomy is
related to the telescope.      -Edsger Dykstra
>
>
>

-- 

Ricardo Fabbri
--
Linux registered user #175401
www.lems.brown.edu/~rfabbri
labmacambira.sf.net
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