Genesis and Sega CD – Audio Filtering(jsgroth.dev)
jsgroth.dev
Genesis and Sega CD – Audio Filtering
https://jsgroth.dev/blog/posts/genesis-sega-cd-audio-filtering/
2 comments
They should watch the Monty video on YouTube
it's a fair watch:
D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org) 3/2/2013 https://youtube.com/watch?v=cIQ9IXSUzuM
D/A and A/D | Digital Show and Tell (Monty Montgomery @ xiph.org) 3/2/2013 https://youtube.com/watch?v=cIQ9IXSUzuM
Only if the frequency being recorded is half the sample rate (a.k.a. the Nyquist frequency) or less. That's the case for that nice pure sine wave in the example, but in more complex cases you'd absolutely be losing information.
Whether the lost information matters of course depends on the frequency range you can actually hear; in the case of CD-quality (44100Hz) audio you probably won't notice any issues unless you're a dog (or unless you're taking a higher-sample-rate recording and downsampling without any kind of anti-aliasing), but the article discusses a PCM chip that natively supports 32552Hz and is receiving a signal that was naïvely upsampled from 16276Hz. Especially in the latter case, you absolutely will hear the information loss.
Whether the lost information matters of course depends on the frequency range you can actually hear; in the case of CD-quality (44100Hz) audio you probably won't notice any issues unless you're a dog (or unless you're taking a higher-sample-rate recording and downsampling without any kind of anti-aliasing), but the article discusses a PCM chip that natively supports 32552Hz and is receiving a signal that was naïvely upsampled from 16276Hz. Especially in the latter case, you absolutely will hear the information loss.
The low-pass-filtered versions all sound noticeably worse to me IMO - like the audio's being smothered under a pillow. Unsurprising, since smothering the treble is usually the point of a low-pass filter.
You haven't lost any information. There is nothing to "figure out" as the analog waveform will be exactly reproduced after the final filter stage.