[opendtv] Re: Please ignore and delete previous message on "Math of oversampling"

  • From: Jeroen Stessen <jeroen.stessen@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 16 Oct 2006 10:14:07 +0200

Dear Mark, 

I can't ignore your message to Tom, because at that time I was also 
involved in generating some "oversampled" images. You have my permission 
to use those too, if you wish. I say this because Tom and I have used 
entirely different methods for bandwidth reduction. Tom used a block-
based (!) DCT and discarded the upper half of the coefficients in the 
frequency domain. (This is asking for blocking artefacts.) I used a 
cascaded downsampling and upsampling (i.e. scalers), which only loses 
the higher frequencies. My method may also introduce a bit of aliasing, 
because during the downsampling the other samples are actually thrown 
away. The perfect experiment would also include an encoding/decoding 
pass on the downsampled signal, which I didn't apply. 

Greetings, 
-- Jeroen

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