5 ms·

Encoding takes >40ms? Opus takes 5-26.5ms. Apparently 150ms[1] is the generally accepted upper bound for call latency. I think the article could do with some b

Encoding takes >40ms? Opus takes 5-26.5ms. Apparently 150ms[1] is the generally accepted upper bound for call latency. I think the article could do with some bandwidth/quality/latency/power comparisons to other codecs. [1] https://en.wikipedia.org/wiki/Latency_(audio) https://en.wikipedia.org/wiki/Latency_(audio)

pjc50 6y ago
Yeah, AMR (for GSM) is 10ms as well.
Bedon292 6y ago
I don't think it is discussing encoding time in the article, it says "features are extracted in chunks of 40ms". My reading is that its breaking down the speech into 40ms chunks, compressing it, and sending that.
- 0b01 6y ago
  But since the buffer size has to be 40ms then so the minimum latency is 40ms
  - zamadatix 6y ago
    Sure latency ends up being 40 ms but that's a function of needing to wait to send the encoded data + network headers at 6 Kbps not a function of the encoder being slow holding everything up.
ksec 6y ago
>These speech attributes, also called features, are extracted in chunks of 40ms, then compressed and sent over the network. So while Encoding doesn't take 40ms, the latency + encoding will indeed be 40ms+. 150ms is the End to End Latency, which is basically everything from Encoding + Network + Decoding. We cant beat the speed of light on our fibre network. We can certainly do something with Encoding and Decoding. And Lyra doesn't seems to help with that case here. Something I pointed out last time Lyra was on HN. I think Opus default to 20ms with option of 10ms slot ( excluding Encoding speed ) at the expense of quality. What we really need is higher bitrate, lower latency and higher quality codec. Which is sort of the exact opposite of what Lyra is offering.
- RL_Quine 6y ago
  > We cant beat the speed of light on our fibre network. Speed of light in what? We can absolutely be faster than fibre optics, which are quite slow relatively speaking (2/3rds that of light in a vacuum).
  - ksec 6y ago
    We wont be replacing Glass Fibre with Vacuum Fibre anytime soon. And I have been following this tech for long, but I do wish I am very wrong.
    - BlueTemplar 6y ago
      Starlink ?
      - tymekpavel 6y ago
        Satellite links are orders of magnitude slower than fiber.
        blendergeek 6y ago
        > Satellite links are orders of magnitude slower than fiber. Minimum end-to-end latency for communications from opposite points of the earth is much lower for Starlink style LEO satellites than for fiber.
        ksec 6y ago
        Which is only in the case of "opposite points of the earth", otherwise you are just adding ~700KM of distance between two point. The point is even if we have perfect Speed of light Data Transfer over a direct line, we are fundamentally limited by it and nothing can be done. But Encoding, Decoding, Time Slots and quality are everything that we have control of and should be look into more seriously.
        6y ago
azinman2 6y ago
Ya I was just coming here to say the same thing. 40ms _just in the codec_ feels like a lot. Because that's not even including time to pull in audio from the hardware (could be 20ms or more in Android devices), time to upload, and time to have it across the Internet, and then time to decode + play on the receiver. That adds up pretty quickly. I'm guessing 40ms was chosen because it is some sweet spot of having enough data to get a worthwhile compression on, but it's one of these things where technology, however impressive it might be, is slowly giving us a worse experience over time in the pursuit of digitization.
- robert_foss 6y ago
  From my understanding the 40ms is just the feature extraction part. The encoding also does quantization, which surely adds to this number.
stefan_ 6y ago
The favorite way to cheat compression contests. Buffer more data, get more compression.
zamadatix 6y ago
There is no such thing as 5ms VOIP audio latency at 6 Kbps, the IPv4+UDP headers would amount to 44.8 Kbps at minimum, so it's irrelevant if one encoder is tuned to be able to encode 5 ms chunks instead of 40 ms chunks. 40 ms intervals requires a minimum of 5.6 Kbps + the codec rate. I.e. at 10 Kbps it's impossible to have a lower VOIP latency than 32 ms. Likely the 40 ms number they tuned for in the real world.

pjc50 6y ago

Yeah, AMR (for GSM) is 10ms as well.

Bedon292 6y ago

I don't think it is discussing encoding time in the article, it says "features are extracted in chunks of 40ms". My reading is that its breaking down the speech into 40ms chunks, compressing it, and sending that.

0b01 6y ago
But since the buffer size has to be 40ms then so the minimum latency is 40ms
- zamadatix 6y ago
  Sure latency ends up being 40 ms but that's a function of needing to wait to send the encoded data + network headers at 6 Kbps not a function of the encoder being slow holding everything up.

ksec 6y ago

>These speech attributes, also called features, are extracted in chunks of 40ms, then compressed and sent over the network. So while Encoding doesn't take 40ms, the latency + encoding will indeed be 40ms+. 150ms is the End to End Latency, which is basically everything from Encoding + Network + Decoding. We cant beat the speed of light on our fibre network. We can certainly do something with Encoding and Decoding. And Lyra doesn't seems to help with that case here. Something I pointed out last time Lyra was on HN. I think Opus default to 20ms with option of 10ms slot ( excluding Encoding speed ) at the expense of quality. What we really need is higher bitrate, lower latency and higher quality codec. Which is sort of the exact opposite of what Lyra is offering.

RL_Quine 6y ago
> We cant beat the speed of light on our fibre network. Speed of light in what? We can absolutely be faster than fibre optics, which are quite slow relatively speaking (2/3rds that of light in a vacuum).
- ksec 6y ago
  We wont be replacing Glass Fibre with Vacuum Fibre anytime soon. And I have been following this tech for long, but I do wish I am very wrong.
  - BlueTemplar 6y ago
    Starlink ?
    - tymekpavel 6y ago
      Satellite links are orders of magnitude slower than fiber.
      - blendergeek 6y ago
        > Satellite links are orders of magnitude slower than fiber. Minimum end-to-end latency for communications from opposite points of the earth is much lower for Starlink style LEO satellites than for fiber.
        ksec 6y ago
        Which is only in the case of "opposite points of the earth", otherwise you are just adding ~700KM of distance between two point. The point is even if we have perfect Speed of light Data Transfer over a direct line, we are fundamentally limited by it and nothing can be done. But Encoding, Decoding, Time Slots and quality are everything that we have control of and should be look into more seriously.
      - 6y ago

azinman2 6y ago

Ya I was just coming here to say the same thing. 40ms _just in the codec_ feels like a lot. Because that's not even including time to pull in audio from the hardware (could be 20ms or more in Android devices), time to upload, and time to have it across the Internet, and then time to decode + play on the receiver. That adds up pretty quickly. I'm guessing 40ms was chosen because it is some sweet spot of having enough data to get a worthwhile compression on, but it's one of these things where technology, however impressive it might be, is slowly giving us a worse experience over time in the pursuit of digitization.

robert_foss 6y ago
From my understanding the 40ms is just the feature extraction part. The encoding also does quantization, which surely adds to this number.

stefan_ 6y ago

The favorite way to cheat compression contests. Buffer more data, get more compression.

zamadatix 6y ago

There is no such thing as 5ms VOIP audio latency at 6 Kbps, the IPv4+UDP headers would amount to 44.8 Kbps at minimum, so it's irrelevant if one encoder is tuned to be able to encode 5 ms chunks instead of 40 ms chunks. 40 ms intervals requires a minimum of 5.6 Kbps + the codec rate. I.e. at 10 Kbps it's impossible to have a lower VOIP latency than 32 ms. Likely the 40 ms number they tuned for in the real world.