In DSP academia (i.e., textbooks, Wikipedia), oversampling and digital filtering are usually tackled as separate topics. Digital audio books (Pohlmann or Watkinson) seem to lump the two topics together.
In digital audio, has there ever been offered a digital filter WITHOUT oversampling?
I think (but, of course, stand corrected) that digital filtering in playback (e.g., CD players and DACs) started with 2x oversampling. I think all 1st-generation CDPs were non-oversampling (D/A) followed by their notorious analog reconstruction (brickwall) filters.
In digital audio, has there ever been offered a digital filter WITHOUT oversampling?
I think (but, of course, stand corrected) that digital filtering in playback (e.g., CD players and DACs) started with 2x oversampling. I think all 1st-generation CDPs were non-oversampling (D/A) followed by their notorious analog reconstruction (brickwall) filters.
When Philips used oversampling (4x ?) in their early CD players it was regarded as a big leap forward. Things were different then, of course, as they thought their job was simply to reproduce as closely as possible the signal emerging from the antialias filter.
Digital mixing desks are full of non-oversampling digital filters. They call that tone control or equalization.
Digital filter vs. oversampling
And ...DSP (tone controls) found in cheap devices like MP3 players and iPods.
But I should've been more clear: digital audio playback. E.g., a digital filter found in its usual before-DAC position. It would be a pretty sharp rolloff (like brickwall). Wonder how this would sound compared to post-DAC analog brickwall filters (common of 1st gen.)?
Of course, digital-filter design (for better gear or even industry/military) is an art + science. So probably big difference between WalMart/cheap and high-end/esoteric.
In any case, with regards to classic digital-audio devices which claim "Oversampling Digital Filter", they are really two different disciplines. Both of which in one monolithic IC (e.g., SAA7220 or PMD100).
And ...DSP (tone controls) found in cheap devices like MP3 players and iPods.
But I should've been more clear: digital audio playback. E.g., a digital filter found in its usual before-DAC position. It would be a pretty sharp rolloff (like brickwall). Wonder how this would sound compared to post-DAC analog brickwall filters (common of 1st gen.)?
Of course, digital-filter design (for better gear or even industry/military) is an art + science. So probably big difference between WalMart/cheap and high-end/esoteric.
In any case, with regards to classic digital-audio devices which claim "Oversampling Digital Filter", they are really two different disciplines. Both of which in one monolithic IC (e.g., SAA7220 or PMD100).
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A non-oversampling digital reconstruction filter would be rather useless; as its output spectrum is periodic with a period equal to its output sample rate, it couldn't filter off any images. At most you might use it to equalize the response of the sharp analogue reconstruction filter.
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