[PD-dev] call for discussion: native video for Pd

[Christian Klippel]

hello miller,

Am Samstag, 27. Mai 2006 19:40 schrieb Miller Puckette:
> To Pd developers,
>
[...snip...]
>
> To begin with at least, I'm hoping to be able to do all video operations
> except storage using floating-point numbers, thereby re-using the usual
> tilde objects.  The disadvantage of this approach is that, if you want to
> "sample" an image, to get decent cache behavior you'd want the possibility
> of storing it in a data-reduced way, as 8-bit integers or perhaps using
> YUYV packing.  (for example, a 512x768 color video frame takes almost 5MB
> to store in floating point, but only about 0.7 MB in 8-bit YUYV.)
>
> So there will probably have to be a suite of new objects for storing 2D
> arrays in fixed point formats, variously trading off memory compaction with
> processing time needed to get the data in and out.  There will probably
> also want to be a choice of interpolation strategies.  Probably the design
> can look like the
> table/tabwrite/tabread/tabread4/tabwrite~/tabread~/tabread4~ objects.
>

uhm .... are you sure about that? first, it doesnt make much sense to use 
floats on images. signed 16 bit integers would be _more_ than sufficient to 
represent a colour channel in a pixel. even film footage doesnt have that 
dynamic range.

using floats would make _every_ processing of video in realtime almost 
impossible, at least on current machines. its just too much data if you 
really want to do some f/x and stuff with it.....

secondly, what do you gain by _storing_ them in the native format, but  
_using_ them as floats? exactly nothing, instead you have the big penality of 
converting back and forth each time. add to that the fact that ram prices are 
really low, so there is no problem anymore to put 2 gigabyte or more into 
your computer.

instead it could pass a void* pointer to the data, that gets casted by the 
processing object to the format it has, and at the same time supplying an 
additional field, like a struct streaminfo{ width, height, current_pos, 
format, whatever.... } that gets evaluated then .... this would also allow 
for streams with different sizes to be used. imagine a stream of a 768x576 
video where you add a 320x240 image .... 

[...snip...]

> ideas and opinions welcome!
>
> cheers
> Miller
>

that was my 0.02 euro-cent .... ;)

greets,

chris


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