Live data from Hacker News

Google open-sources the Lyra audio codec

opensource.googleblog.com

11–20 of 145 posts

Re: Google open-sources the Lyra audio codec

#11

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)

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

Re: Google open-sources the Lyra audio codec

#12

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)

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.

Re: Google open-sources the Lyra audio codec

#13

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)

>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.

Re: Google open-sources the Lyra audio codec

#14
One thing I'm slightly worried about "machine learning" in compression rather than conventional everything-is-sines mathematical approaches is the possibility of odd nonlinear errors. Remember the photocopier that worked by OCR and would occasionally mis-transcribe numbers?

I don't mind compressing a phoneme to as much as I would mind it compressing it to a clearly audible different phoneme.

Re: Google open-sources the Lyra audio codec

#17

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)

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.

But since the buffer size has to be 40ms then so the minimum latency is 40ms

Re: Google open-sources the Lyra audio codec

#18

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)

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.

Re: Google open-sources the Lyra audio codec

#19
post #13

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)

>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…

> 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).

Re: Google open-sources the Lyra audio codec

#20
post #14

One thing I'm slightly worried about "machine learning" in compression rather than conventional everything-is-sines mathematical approaches is the possibility of odd nonlinear errors. Remember the photocopier that worked by OCR and would occasionally mis-transcribe numbers? I don't mind compressing a phoneme to as much as I would mind it compressing it to a clearly audible different phoneme.

>Remember the photocopier that worked by OCR and would occasionally mis-transcribe numbers?

For those who don't remember: http://www.dkriesel.com/en/blog/2013/0802_xerox-workcentres_...

Post reply on HN