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Altera_Forum's avatar
Altera_Forum
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16 years ago

help needed : upscaling video

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

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    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's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    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.