Quote:
Originally Posted by DNSB
At one point, I was involved with a group that developed a playback device that sped up and frequency shifted audio to allow playing back voice recordings at higher speeds. It could get up to 300-325WPM without sounding too bad but at 400WPM, you were definitely getting into chipmunk territory.
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I forgot about the frequency shifting. Way back in the good ol' days there were cassette recorders for dictation/note taking that could speed it up, and I think without needing to fix the frequency.
Then way back when I worked in a computer music research place one guy wrote something he called the phase vocoder. It could change the duration of a recording and keep the pitch/frequencies the same, or vice versa, change the pitch and keep the duration the same. It was computationally expensive but that was when cpu speeds were measured in kilohertz and ram was in single digit megabytes.