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

[Vilson Vieira]

How to set high priority for audio Pd instance and lower priority to the
other instance?

All the best.

2011/11/14 Ricardo Fabbri <rfabbri at gmail.com>

> 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 <http://www.lems.brown.edu/%7Erfabbri>
> >> labmacambira.sf.net
> >>
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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 <http://www.lems.brown.edu/%7Erfabbri>
> labmacambira.sf.net
>
>
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-- 
Vilson Vieira

vilson at void.cc

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