[PD] need a workaround for detecting movement in Mac OS

[chris clepper]

I used pix_movement and blob for basic motion detection for years.  I gated
the video signal so it would only output every half second or second because
it is usually counter-productive to have 25 or 30 updates a second for this
task.

As to your problem, it might come from how your device/driver reports (or
doesn't report) new frames.  Try setting the GEM framerate to the advertised
frame rate of your device and see if that helps.  Note, that lots of webcams
claim 30fps, but only deliver 15fps or less.

On Tue, Apr 5, 2011 at 7:53 AM, Matteo Sisti Sette <
matteosistisette at gmail.com> wrote:

> Hi,
>
> Bug 3191771 renders the combination pix_video+pix_movement useless in Mac
> OS unless you can lower gem's framerate to ensure it is lower than the
> camera's framerate (which is not always an option), or unless one finds some
> other workaround.
>
> The problem is that whenever a new frame from the camera is not available,
> pix_movement computes the new input frame as a black frame, and hence the
> resulting difference is almost all-white.
>
> Note that the problem is NOT that pix_movement computes the difference
> between two identical frames yelding a black frame as a result. It's worse:
> when the new frame is not available, it seems it considers it as an
> all-black frame, so the output is the difference between a real frame and a
> black frame. That causes white flickering, not black flickering.
>
>
> Does anybody use pix_movement and pix_video on Mac OS? How do you work
> around this issue?
>
> Ideally I would like to find a simple and easy-to-understand solution,
> because I am teaching a Pd course and I'd like to give the students (most of
> whom use Mac) a workaround they can understand.
>
> Thank you in advance
> m.
>
> _______________________________________________
> Pd-list at iem.at mailing list
> UNSUBSCRIBE and account-management ->
> http://lists.puredata.info/listinfo/pd-list
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.puredata.info/pipermail/pd-list/attachments/20110405/da046cc3/attachment.htm>