Re: [video] Real Time Video Scaling

[Aris Konstantinos <konstantinos_aris@hotmail.com>]

Hi Gents;

Please correct me if I am wrong..A FIR Filter is used if there is a need to 
skip some parts of the frequency spectrum of a signal, rigth?. Could you 
please give us some more information or some resources that we can 
readly follow for this purpose? At last, what are the specifications of the 
FIR Filter (ex:is this Pass-Band, what is the sampling frequency 
selected)? 


cheers, :)

Aris


----- Original Message ----- 
From: Richard Herveille <richard@a... > 
To: video@o...  
Date: Mon, 26 May 2003 07:50:44 +0200 
Subject: Re: [video] Real Time Video Scaling 

> 
> 
> 
> 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. 
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