help needed : upscaling video

[Altera_Forum]

Hi, 

 I am using altera VIP suit , ver 8.0 and Quartus II ver 8.0. And using 3c120 development board.   In the current design, i need to upscale the video from 720x576 PAL to minimum 800x600 ... However, the quality of the upscaled image is not very good and video looks pixelated. In the scaler, I am using polyphase algorithm with Lancoze 2 coefficients.   I tried increasing number of filter taps upto 12 for both vertical and hosrizontal filters in scaler. Also changed the coefficients from lancoze 2 to lancoze 3 ..   I tried to set the resolution to 800x640 so as to maintain the H/W ratio.  But the still the video quality is same.   Any pointers, how to decide the number of filter taps required and the coefficients ? Do I need to manually provide coefficients for upscaling or one of the given lancoze coefficients would do.   Thanks in advance.  Regards, Foram

[Altera_Forum]

Hello, 

 Quoting the VIP user guide, scaling up with any input/output resolution: 4 taps, 16 phase Precision: Signed, 1 integer bit, 7 fraction bits Coefs: Lanczos-2, or Bicubic  I believe you should stick to these recommendations. In practice it usually looks worse when using more than 4 taps for upscaling.  I assume you are using the motion-adaptive deinterlacer before the scaler. If not and if the quality is not as good as expected you should probably start from there.  Kind regards, vgs

[Altera_Forum]

For upscaling video, you don't want a big filter, I would instead use the scaler in either bicubic or even bilinear mode. Try bilinear mode first. 

 Jake

[Altera_Forum]

Thanks Vgs and Jake. 

 I am using motion adaptive deinterlacer. and I also used the scaler setting mentioned by Vgs before trying the 12 tap filter.   However, I have not tried with bicubic or bilinear mode. Will try using this mode first.   Thanks a lot.