27 ms·
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 encodin
by vortico 8y 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.
- bch 8y agoSo, 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_signaling https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_sign... [1] https://en.m.wikipedia.org/wiki/Presbycusis https://en.m.wikipedia.org/wiki/Presbycusis
- vortico 8y agoNo, 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.
- bch 8y agoAhhh... 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.
- aidenn0 8y agoV.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.