Re: [video] Real Time Video Scaling

[Richard Herveille <richard@asics.ws>]

Well down scaling is the easiest, especially if you can afford loosing pixels. 
Simply skip every second pixel and skip every second line.
This doesn't give the best picture, but it will work. Biggest problem is that 
a line 1 pixel/line width won't be visible when it's on the removed 
pixel/line. You can solve this by alternating what pixel/line you remove, but 
then the image starts flickering (pixel visible, non visible, visible, non 
visible, etc)

A better way is to filter the image using a reducing filter. This can/should 
be a simple FIR filter. The output of this filter provides a much smoother 
image and provides all the features of the original. This can be done on the 
fly for a single line. But in order to filter lines you need some memory, but 
not an entire frame.

Upscaling (zooming) is best done with a bi-linear filter. You need to store 
the previous line for this.


> Hi all;
> I have been thinking on a problem. Some of you might have an idea.
>
> The problem is : real time 640x480 video scaling without frame buffering.
> Is there a way to downscale(eq: 320x240) or zooming a specific part of
> a screen without performing any framebuffering?? System clock is of
> course 25Mhz.
>
> Note: Pixel loss is not a big deal. You can ignore some pixels if
> neccessary.
>
>
> Hope to hear some ideas..
>
> See ya,
> Cheers,
>
> Aris


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