A quick look inside a Yamaha KX-393 cassette deck from the 90s, and demo of Dolby noise reduction. That damn tape counter gives away all the times I cut out my failure to speak properly. =P
Headphones are recommended for the noise reduction demo.
The waveforms displayed while Dolby is selected are simulations - versions of the original audio processed by a compressor/expander. In reality, Dolby mostly only affects the treble (as you can hear), since that's where most of the tape hiss is, so you wouldn't get big low-frequency waves, but hey, it's easier to visualise this way.
My usual video editor did not feel like working, so I made this entire thing in Avisynth - it's like coding, but for video. Please kill me now. Well, I used VirtualDub for the cropping out of all the dead air, my failures to speak, and misinformation which I said by mistake. On the plus side, I learned a lot of stuff by editing this way (such as how badly Avisynth is designed regarding modifying audio). Also, I didn't have to screen-capture anything to get those waveforms - they're being made in realtime by the Waveform plugin, which is processing audio from different Dolby simulations which are also being made in realtime by SoxFilter's "compand" function.
This video didn't turn out as well as I would've liked - from the poor view of the mechanism to the incomplete demonstration of the functions and different tape types, and the fact that the only time I could record this (free of disturbances and noise) was a 45-minute slot was when I was half-asleep. So, if people are interested, I might re-visit this.
With all the old technologies on my channel such as a dot matrix printer, FM MIDI synth, SC-88Pro and now a cassette recorder, perhaps I should rename my channel to "SomethingRetro". There's an old VCR here just waiting to be opened, too...
