[PD] pix_motion_sector

Hans-Christoph Steiner hans at at.or.at
Fri May 14 17:43:44 CEST 2010


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 at iem.at>:
>>> -----BEGIN PGP SIGNED MESSAGE-----
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>>> Jaime Oliver wrote:
>>>> On Thu, May 13, 2010 at 7:40 PM, Mathieu Bouchard <matju at artengine.ca 
>>>> >wrote:
>>>>
>>>>> 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
>>>>
>>>>> _ _ __ ___ _____ ________ _____________ _____________________ ...
>>>>> | Mathieu Bouchard, Montréal, Québec. téléphone: +1.514.383.3801
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
>>>>
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>>
>>
>
>
>
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