4 ms·

Example?

by bch 8y ago

Example?

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 ago
  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_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 ago
    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.
    - bch 8y ago
      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.
- aidenn0 8y ago
  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.
aidenn0 8y ago
pre-echo will appear on very fast attacks; clapping, some types of drums and castanets are usually cited as the worst. Some styles of electronic music have fast attacks as well. With older encoders, cymbals were terrible, but lame's psychoacoustic model is pretty good at masking those artifacts these days (at least at high bitrates). For examples, some quick searching on hydrogen audio found a couple songs reported to be ABX distinguishable with lame and after previewing the songs, they do in fact have a lot of quick attacks: Human Disease by Slayer (Some very fast and cleanly played drum parts; also it's mostly not snares; snares sound terrible at low bitrates, but I personally can't distinguish high-bitrate snares from uncompressed snares) Show Me your Spine by PTP (The "instrument" used for the base rhythm has an unnaturally short attack).
PavlikPaja 8y ago
Any sound that starts or end very suddenly. Drums of any kind will sound kind of weird in MP3. Applause used to be the bane of MP3. Encoders got better at it, but it's apparently impossible to get rid of completely. As far as I understand it it's the accoustic equivalent of ringing artifacts that you can see in low quality JPEG's or old MPEG videos.
- deleted 8y ago
  [deleted]
Tomte 8y ago
https://www.youtube.com/watch?v=MtiRBFWkRKs https://www.youtube.com/watch?v=MtiRBFWkRKs beginning at 54 seconds. I don't really hear the pre-echo. Actually I love that I don't hear compression artifacts in music or see them in JPEGs. Makes my gear so much cheaper. :-)

Example?

by bch 8y ago

Example?

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 ago
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_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 ago
  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.
  - bch 8y ago
    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.
aidenn0 8y ago
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.

aidenn0 8y ago

pre-echo will appear on very fast attacks; clapping, some types of drums and castanets are usually cited as the worst. Some styles of electronic music have fast attacks as well. With older encoders, cymbals were terrible, but lame's psychoacoustic model is pretty good at masking those artifacts these days (at least at high bitrates). For examples, some quick searching on hydrogen audio found a couple songs reported to be ABX distinguishable with lame and after previewing the songs, they do in fact have a lot of quick attacks: Human Disease by Slayer (Some very fast and cleanly played drum parts; also it's mostly not snares; snares sound terrible at low bitrates, but I personally can't distinguish high-bitrate snares from uncompressed snares) Show Me your Spine by PTP (The "instrument" used for the base rhythm has an unnaturally short attack).

PavlikPaja 8y ago

Any sound that starts or end very suddenly. Drums of any kind will sound kind of weird in MP3. Applause used to be the bane of MP3. Encoders got better at it, but it's apparently impossible to get rid of completely. As far as I understand it it's the accoustic equivalent of ringing artifacts that you can see in low quality JPEG's or old MPEG videos.

deleted 8y ago
[deleted]

Tomte 8y ago

https://www.youtube.com/watch?v=MtiRBFWkRKs https://www.youtube.com/watch?v=MtiRBFWkRKs beginning at 54 seconds. I don't really hear the pre-echo. Actually I love that I don't hear compression artifacts in music or see them in JPEGs. Makes my gear so much cheaper. :-)