On Wed, 2005-03-09 at 09:35 +1300, E.Chalaron wrote: > Now another thing, at the risk of appearing completely dumb, what is the > purpose of y4mspatialfilter ? is it a convolution filter ? if so is there a > way I can cut off frequencies to avoid the Nyquist effect ?
y4mspatialfilter performs a convolution with a 2D (spatial) lowpass filter. It uses Lanczos-weighted sinc coefficients, and you can control the cutoff frequency and the transition sharpness (=filter length). Its purpose is to remove high-spatial-frequency noise to reduce bitrates without reducing the video frame size. For low-bandwidth video (like from VHS) you can remove a lot this way, for high-bandwidth video you risk blurring if you get too aggressive. I assume by "Nyquist effect" you mean aliasing; while y4mspatialfilter could be used as a general antialiasing filter before a subsample, the preferred scaler (y4mscaler) already has very flexible antialiasing built in. Indeed, if y4mscaler were to allow the filter bandwidth to be independent of the scaling ratio then y4mspatialfilter would be rendered obsolete. Dan ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
