[PD] PS3eye macam pix_video duplicate frames

[chris clepper]

The Quicktime model for devices like cameras does not work well with GEM.
Quicktime is designed to control all of the rates for audio and video (and
final display) internally using clocks that are not accessible from the
API.  Since Pd/GEM has its own rendering engine and clock, efforts must be
made to try to reconcile the QT model with GEM.  Because video capture is a
real time process there is no way to know which frame you are on (it's
basically a one frame movie), so 'gimmieTheNextFrame() doesn't work, and
the work around is to guess if you have a new full frame or not.  I think
the technical term for this process is a 'hack'.

If the device driver is being a bit of a bitch, I highly suggest using
another device.  In particular professional video devices (DV cams,
anything made by AJA or BlackMagic) work pretty well.  At least those are
the devices I wrote the code for...

On Thu, May 3, 2012 at 10:46 PM, William Brent <william.brent at gmail.com>wrote:

> Hi list,
>
> I've been banging my head against a wall trying to understand why I'm
> getting duplicate frames from the PS3seye camera using the
> macam-cvs-build-2009-09-25 driver.  This is using Gem 0.93.3 with Pd
> vanilla 0.42-6 on a Macbook Pro 2.53 Ghz i5, OS 10.6.8.
>
> No matter what frame rate I set in the macam driver dialog via GEM, I
> get at least 2 duplicate frames.  The attached patch is the simplest
> case with single buffer mode for the gemwin.  When I bang the gemhead
> to see the next frame, I get duplicates using the PS3eye.  When I use
> the built in camera, no duplicates.  Can anyone with a similar setup
> confirm this?
>
> Thanks for any and all insight,
> William
>
>
> --
> William Brent
> www.williambrent.com
>
> “Great minds flock together”
> Conflations: conversational idiom for the 21st century
>
> www.conflations.com
>
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