[PD] #store and getting pixel data from a movie file

ALAN BROOKER alan.brooker2010 at gmail.com
Fri Aug 26 00:27:56 CEST 2011


Hey Mathieu,

Thanks for the tips much appreciated, I'm going to to work on
something to extract sounds from video movements/colours basically.
I've done this in Gem with pix_data & pdp with pdp_cog - trying out
gridflow as I think there could be more ways of extracting values to
explore


I dont think gridflow likes the mp4 suffix? the console displays
[gf/io_generate 1012in] unknown suffix  'mp4'  .Changing the suffix
file manually from mp4 to .mov seems to resolve the issue though

Thanks again

On Wed, Aug 24, 2011 at 6:10 PM, Mathieu Bouchard <matju at artengine.ca> wrote:
> On Tue, 23 Aug 2011, ALAN BROOKER wrote:
>
>> I hope to ask for some tips regarding obtaining values from a loaded
>> image/movie file by using gridflow ? #store gets can get rgb values
>> from a specified pixel position
>
> You can pass multiple pixel positions at once to #store and it's much faster
> than getting pixels one by one. Those multiple pixel positions can in turn
> be organised in rows and columns so that you can make a new image by picking
> 100000 pixels in a single step, for example.
>
>> but any advice on getting the whole dimensions at once
>
> What does that mean ?
>
>> (or any other techniques in getting gridflow to output values from a movie
>> file such as movement, luminosity or anything)?
>
> some kind of luminosity is what you get when you convert to greyscale. You
> may use [#rgb_to_greyscale].
>
> Movement can be a lot of different things.
>
> The easiest one is to subtract each frame with the previous one. Then you
> can know the change of luminosity from one image to the other, or the change
> of each channel. You do that using [t a a] and [# -] (plain diff) or [# sq-]
> (squared diff) or [# abs-] (absolute diff).
>
> You can also identify regions or compute mean positions of things and then
> look at the position differences. Sometimes I did that using [#moment] and
> then [t a a] and [# -]. Note that often the same tools work on different
> kinds of data (pixel colours vs pixel positions). This is a feature of
> GridFlow which is not found in other image-processors of Pd (GEM/PDP/etc).
>
> There are also algorithms to make a map of all translations (move) of pixels
> in the picture, but they have not incorporated in GridFlow.
>
>> ...also is there support for mp4 in gridflow? the file format being the
>> same as mov (I think?)
>
> GF uses Quicktime.framework (by Apple) on OSX, and libquicktime (by H.W. &
> Plaum) on Linux and now also on OSX. Nearly all video file format support
> rests upon that.
>
> GF also can run libmpeg3, but that's a MPEG1/MPEG2 decoder without plugins.
>
>  _______________________________________________________________________
> | Mathieu Bouchard ---- tél: +1.514.383.3801 ---- Villeray, Montréal, QC
>



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