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How Does FaceTime Work?

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Re: How Does FaceTime Work?

#41

Post by throwthere »

dylan604 wrote: post #38
jonathanlydall wrote: post #36

I find FaceTime video calls really superb, but for whatever reason the audio only calls have short (sub-second length) moments where it cuts out and it's very disconcerting. This happens when calling both my parents and my brother, both of which are only KMs away and like me have 25Mb/s or faster fibre connections. Strangely I've never noticed this audio problem during video calls. So I tend to do voice only calls us…

If you have 25Mb/s connection while anyone on the other end has only 1.5Mb/s connection, then you have a 1.5Mb/s connection. Just because you pay for fiber doesn't mean you always get that speed. Most benefits of highspeed badwidth at home allows for multiple connections to reach their "full" speed without forcing other connections to lower speeds.

Even if you have a 1.5Mb/s connection you should hear crystal clear audio.

Re: How Does FaceTime Work?

#42

Post by criddell »

mosselman wrote: post #15

We used to use Skype with my wife's parents and it sucked: there were delays, freezes, low quality video, etc. It worked great with my mother, but she had far better internet than my wife's parents. The alternatives were even worse: Telegram, whatsapp, jitsi. Then we tried FaceTime: the difference was night and day. Everything was smooth, the sound was better, no stuttering, we could actually read things they held to…

At one time, you could configure Skype to make a point-to-point call and the quality was great provided both endpoints had high bandwidth, low latency connections. Microsoft changed it to make all calls go through their servers and the quality took a big hit.

Re: How Does FaceTime Work?

#43

Post by dylan604 »

dahfizz wrote: post #18
lqet wrote: post #16

> For those of you old enough to remember landlines, it reminds me of those [...] When we all switched to cell service audio quality took a huge hit I don't understand - are landline phones not in use anymore? I only use a landline phone to communicate with the family, because I simply cannot stand the audio quality of cellphones for calls which last longer than a few minutes. Edit: In Germany, there are about 40 M a…

Everyone already has cellphones, so a landline is an extra monthly cost for something that you're already paying for.

Unless you're of a certain age. People that already had long established landlines continue to pay for them even after getting a cell phone. And people still call them on those numbers as thats the number people know and remember vs just storing a cell number in their contacts.

Also, for people getting an internet signal from the phone company (DSL), the landline was usually bundled in a package. They tried to make them viable for as long as possible.

Re: How Does FaceTime Work?

#44

Post by kkielhofner »

TonyTrapp wrote: post #20

Strange preamble: I found the quality of analog landlines to be terrible. Since we got switched over to VoIP, the voice quality is crystal-clear if the person on the other end also has a VoIP connection. It almost sounds too good. Better than most online voice chat stuff.

Interesting human psychology note: I was involved in some early deployments of HD-ish codecs. HD codecs are considered to be anything that provides greater than the (less than) 4kHz frequency response of the traditional PSTN. At the time "HD audio" was generally 8kHz frequency response (16 kHz sampling rate because of Nyquist-Shannon[0]).

This was around 2009 and many users, having not experienced that kind of frequency response/fidelity were kind of "unnerved" by it because (as you say) it can sound "too good". Users were freaked out by the extended frequency response and added fidelity. A common complaint was that previously undetectable breath sounds, etc were audible.

"These days" with FaceTime, WebRTC, etc sampling rates go all the way to 48 kHz, being able to represent the entire range of human hearing (and far beyond the range of human speech[1][2]). Not only have people become more used to the extended audio range, various other parts of the stack (quality microphones/hardware, speech detection, noise cancellation, etc) has caught up and some of those early pesky issues like breath sounds, etc have been largely addressed.

[0] https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampli...

[1] https://en.wikipedia.org/wiki/Voice_frequency

[2] https://www.frontiersin.org/articles/10.3389/fpsyg.2014.0058...

Re: How Does FaceTime Work?

#45

Post by elzbardico »

the-dude wrote: post #21
lqet wrote: post #16

> For those of you old enough to remember landlines, it reminds me of those [...] When we all switched to cell service audio quality took a huge hit I don't understand - are landline phones not in use anymore? I only use a landline phone to communicate with the family, because I simply cannot stand the audio quality of cellphones for calls which last longer than a few minutes. Edit: In Germany, there are about 40 M a…

Landlines have been digitized too, a distinct difference to what an analog landline offered. It was more intimate, you could hear breathing for example.

I think that at least for long distance calls, landline calls have been digitized and packet switched since the 70's, didn't they?

Re: How Does FaceTime Work?

#46

Post by dylan604 »

the-dude wrote: post #21
lqet wrote: post #16

> For those of you old enough to remember landlines, it reminds me of those [...] When we all switched to cell service audio quality took a huge hit I don't understand - are landline phones not in use anymore? I only use a landline phone to communicate with the family, because I simply cannot stand the audio quality of cellphones for calls which last longer than a few minutes. Edit: In Germany, there are about 40 M a…

Landlines have been digitized too, a distinct difference to what an analog landline offered. It was more intimate, you could hear breathing for example.

It was also more hackable. You could litterally open up one of those grey phone company stumps with a 7/16" socket, and then just start rewiring the connections. I had a friend that knew which cables ran to their house, and could use a couple of wires to jump them to another line. They were able to "borrow" someone's line and routed to the 2nd twisted pair for their house. They rewired the phone jack in their room to have a 2nd line. Everything was good until they forgot to unplug the phone while they were not home, and someone rang the other house and it rang in their room while the parental units were home.

Re: How Does FaceTime Work?

#47

Post by the-dude »

wanderingstan wrote: post #37
the-dude wrote: post #21

Earlier quoted context omitted.

Landlines have been digitized too, a distinct difference to what an analog landline offered. It was more intimate, you could hear breathing for example.

I had forgotten about hearing breathing; you’re absolutely right it was more intimate.

As I remember it, one could be silent and still be together.

Re: How Does FaceTime Work?

#48

Post by kkielhofner »

webmobdev wrote: post #31
lqet wrote: post #16

> For those of you old enough to remember landlines, it reminds me of those [...] When we all switched to cell service audio quality took a huge hit I don't understand - are landline phones not in use anymore? I only use a landline phone to communicate with the family, because I simply cannot stand the audio quality of cellphones for calls which last longer than a few minutes. Edit: In Germany, there are about 40 M a…

It is on the decline in India too: > In the past decade, landline subscriber base has been on a decline, with connections reducing from 36.76 million as of 31 January, 2010 to 20.58 million as of 31 January, 2020. Of the total telecom 1.18 billion connections, only 20.26 million, or less than 2%, were landline as of February. - https://www.livemint.com/industry/telecom/trai-says-declinin... (And yes, landline phones…

I used to joke that even with extended frequency response, etc cell phones and VoIP can certainly sound worse. I would compare the Sprint "pin drop" commercials[0] to the (at the time) Verizon Wireless "Can you hear my now?" campaign[1] with the joke being - progress from a pin drop to yelling "Can you hear me know? How's this? Is this better? Sorry about that." 20 years of progress!

Of course now (for the most part) packet loss concealment and other advanced technologies have equalized a bit of this but there are still days where I miss B-channels on a T1 PRI.

[0] https://www.youtube.com/watch?v=k4dIDl8sjJk

[1] https://www.youtube.com/watch?v=Lo0xsZCRp4g

Re: How Does FaceTime Work?

#49

Post by EGreg »

elzbardico wrote: post #45
the-dude wrote: post #21

Earlier quoted context omitted.

Landlines have been digitized too, a distinct difference to what an analog landline offered. It was more intimate, you could hear breathing for example.

I think that at least for long distance calls, landline calls have been digitized and packet switched since the 70's, didn't they?

No. Otherwise why would things cost $3 a minute until VOIP?

Re: How Does FaceTime Work?

#50

Post by jeffbee »

the-dude wrote: post #21
lqet wrote: post #16

> For those of you old enough to remember landlines, it reminds me of those [...] When we all switched to cell service audio quality took a huge hit I don't understand - are landline phones not in use anymore? I only use a landline phone to communicate with the family, because I simply cannot stand the audio quality of cellphones for calls which last longer than a few minutes. Edit: In Germany, there are about 40 M a…

Landlines have been digitized too, a distinct difference to what an analog landline offered. It was more intimate, you could hear breathing for example.

You mean packetized. Digital isochronous landline services existed for decades. The "T" system was deployed by AT&T in 1962. Digital telephony is in fact awesome. There's no reason why "digital" needs to mean "it sucks". The reason voice over mobile networks sounds terrible is because traditional landline service uses a 64kbps isochronous channel and lossless 8-bit/8kHz coding, while mobile uses a voice estimation model that transmits its parameters every 20ms at ~3-6kbps and suffers from frequent frame loss. VoIP can sound much better than mobile but may occasionally suffer delay and loss which never happened with traditional telephony.
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