I'll update the helpfile for [pix_motion_sector] to include a subpatch that does the same thing with [pix_crop], [pix_movement], and [pix_dump]. I think I might also change the source and try taking the distance between current/previous frames using all RGB info instead of a greyscale approximation. The speed issue aside, that may be a significant difference from [pix_movement] worth investigating.
On Fri, May 14, 2010 at 8:43 AM, Hans-Christoph Steiner hans@at.or.at wrote:
I'd love to see an example implementation of this as a patch, if anyone is up for it. A lot of students ask me for this kind of video tracking. It would be good to add to the video tracking examples.
.hc
On May 14, 2010, at 10:11 AM, Jack wrote:
Le vendredi 14 mai 2010 à 06:49 -0700, William Brent a écrit :
I implemented Miller's phase vocoder from the documentation in C and was amazed to see that the CPU load was exactly the same. So much for improving efficiency... But I have seen a big difference for traversing tables and lists. The process of summing the elements in a large table is much faster in an extern than with an [until] loop.
In the case of [pix_motion_sector], what's the easiest way to duplicate the functionality of reporting % of pixels changed in the region? Is there an obvious way to count up the number of pixels that crossed [pix_movement]'s threshold in the cropped region?
[pix_dump] ? Maybe a faster method ? ++
Jack
2010/5/14 IOhannes m zmölnig zmoelnig@iem.at:
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Jaime Oliver wrote:
On Thu, May 13, 2010 at 7:40 PM, Mathieu Bouchard matju@artengine.cawrote:
On Thu, 13 May 2010, William Brent wrote:
Yes - it's exactly that: an adaptation of pix_movement that lets you > > specify an area to analyze. That way you can use several instances > to > create multiple regions for triggering different events. I haven't > looked > at this in two years! I'll take a look at the helpfile and see > what's > missing/unclear. > what's the difference between that, and using [pix_crop] and [pix_movement] with [pix_separator] ?
Please correct me if I'm wrong, Doesn't having these as externals instead of abstractions, make it significantly faster/efficient? particularly if you have many of them?
no not necessarily. the overhead for message communication between objects is usually quite small, compared to the pixel operations.
you would only need [pix_crop]->[pix_movement] without the [pix_separator] (since the crop will have to allocate a new image anyhow), thus no need for the extra copying of data.
the only speedup you could expect from pix_motion_sector (i haven't looked at the code), is that you wouldn't have to copy the data for cropping at all, but only use the pixels in the ROI.
as for williams argument, that you need less objects, i would suggest looking into abstractions :-) it's definitely less lines of code (at a minimum 10 lines of Pd code) and still only a single object...
mfgasdr IOhannes
best,
J
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