Comment by vortico
7 years ago
Playing a set of high-frequency pure sine waves is the failure point for MP3, AAC, Vorbis, and Opus. Dial-up noises are close to this, which you can try encoding/decoding. And this is no surprise, since the point of the V.90/92 protocols is to cram as much information as possible into analog frequencies, and the point of psychoacoustic lossy codecs is to remove the least efficient frequency information of our log-frequency scaled ears.
But this is kind of a pedagogical example. Not the point of who you're responding to.
So, a high frequency DTMF[0] construction should render a pre-echo? What’s the lowest definition of “high” pairs that would satisfy showing this encoding breakage but be hearable by a majority of people[1]?
[0] https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_sign...
[1] https://en.m.wikipedia.org/wiki/Presbycusis
No, pre-echos are unrelated to high-frequency sine waves. And DTMF aren't what I'd consider high-frequency. I'm talking about 4-20kHz.
Ahhh... I think I misunderstood your “dialup noises” as dial tone noises. You’re talking about the high pitched squelch-y initial negotiation of a modem.
V.90 and V.92 both sound largely like spectrally shaped noise. Even if you give very regular inputs, the data is compressed and scrambled, then spectrally shaped and then output as 8-bit 8kHz log-weighted PCM.