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That is very impressive! I wonder if a WaveNet decoder could be built for phone calls, as those still sound awful. If it's possible to do this only on the decod

That is very impressive! I wonder if a WaveNet decoder could be built for phone calls, as those still sound awful. If it's possible to do this only on the decoder side you don't have to wait for your network to start supporting HD voice or VoLTE to get better quality audio!

IshKebab 8y ago
Actually if you're lucky and make a phone call with HDVoice, or whatever they're calling it, the quality is excellent. It makes a huge difference. Unfortunately the place where you really want good quality is call centres - it's often hard to hear people and half of the reason is the shitty POTS quality - and call centres will probably get HDVoice in about 40-50 years. Maybe. Edit: nm should have read all of your comment before replying!
- reaperducer 8y ago
  >Actually if you're lucky and make a phone call with HDVoice, or whatever they're calling it, the quality is excellent Can confirm. I spend a lot of time in fringe reception areas, but every now and then I get a good, strong signal and the HD Voice kicks in between my iPhone and my wife's and it sounds like she's standing right next to me. It really is something to experience, especially if the previous phone call was over regular tech. Back when AT&T was running the "You get what you pay for" ads to combat SPRINT and MCI, it had a service you could sign up for that would give your landline phone calls amazing quality. Sadly, a majority of people would rather pay less for crap than more for quality; even back then.
  - namibj 8y ago
    Also why no one really appreciated ISDN over here in central Europe. Yes, there are ways to do better _now_, and it would have been trivial to support channels with better codecs by negotiating something different than u-law 8kHz PCM, but back then that resulted in rather good quality. The issue was that few people got ISDN phones, which resulted in them using analog outputs on an adapter device, which got later incorporated into the internet router, which at one point switched from ISDN to VoIP. And people plug a phone via an analog jacket into the router, instead of using a VoIP capable phone or even anything digital. While many do use DECT cordless phones, those rarely use the DECT hardware inside the router, and instead use the one in the charging dock, which itself connects via an analog, POTS-bandpass-filtered, phone jacket to the VoIP router. Oh well, we will probably never get that kind of quality, which is only possible with QoS on the whole path, if there is any congestion. That is the one thing something like rocket.chat and discord can't provide. Edit: the way to do this is to force quality upon people, wherever you won't drive them away with the cost this incurs. That way people will associate your brand as a whole with the quality, i.e., in that case, people will associate AT&T with quality, not AT&T premium. Normal people do not even know what kind of plan they are on, except for about one hour before and after they sign the contract.
    - gsich 8y ago
      >Also why no one really appreciated ISDN over here in central Europe. Except Germany. Which had probably the best telephone system in the world when they deployed ISDN nationwide.
      - namibj 8y ago
        I am speaking as a German. Sure, larger businesses used proper ISDN, but your uncle/mom didn't. The best you could hope for there was only DECT compression, aka ADPCM 4bit/8kHz.
        gsich 8y ago
        Sure they did. Adoption rate was about 30%, possibly even higher at it's peak. DECT codec is useless if it's transmitted through analog lines, as it gets converted to standard 3.4k-Hz quality anyway. Except for in-house calls of course.
    - bewo001 8y ago
      The problem with land line voice quality is that people expect a land line phone / VoIP adapter to cost like 20 USD or Euro. At this price point you can't have fancy codecs and audio hardware that delivers a decent signal. Bad audio hardware with a good codec can actually decrease audio quality (the mic's noise no longer gets filtered as it is with 8kHz PCM).
  - heywire 8y ago
    I think it was AT&T that had a test number you could call to hear a higher quality phone call (I was pretty young at the time, so my memory is fuzzy). I remember it sounding very good, but that test number was the only time I remember hearing that quality over the POTS. The VoLTE and HD voice I occasionally get on my iPhone reminds me of that system.
- gsich 8y ago
  What do you mean with "HDVoice"? On landline connections this usually means G722. G711u/a is definitly not "HD".
  - namibj 8y ago
    I assume the usual wideband codecs used with VoLTE.
  - IshKebab 8y ago
    I don't know what technology it is specifically, but it's a brand name they used for actual high quality calls. Think, 128 kB/s MP3, rather than the standard cups-and-string quality. It only seems to work on mobile.
    - gsich 8y ago
      I know the difference, used G722. On mobile its G722.2, a totally different codec, but with the same ~7KHz range. But there were some companies that advertised a lower frequency range as "HD".
  - ahoka 8y ago
    He probably means Adaptive Multi-Rate Wideband (AMR-WB) [1], AKA G.722.2. There is a common misconception that it is VoLTE only, but actually it works pretty well on 3G too. It is night and day compared to legacy codecs. 1. https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_Wideband https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_Wideband
skykooler 8y ago
I'm curious as to how fast the WaveNet decoder is? The last time I saw an article on it, it took multiple minutes to generate a second of audio.
- gwern 8y ago
  The original WaveNet repeated a lot of computations; with caching/dynamic programming, it became a lot faster. Other optimizations were also doable. In any case, that was eventually made moot by using model distillation to train a wide flat (not deep) NN, which is 20x realtime: https://deepmind.com/blog/high-fidelity-speech-synthesis-wavenet/ https://deepmind.com/blog/high-fidelity-speech-synthesis-wav... (This was necessary to make it cost-effective to deploy onto Google Assistant.)
dredmorbius 8y ago
Chaining codecs arbitrarily tends to create really bad artifacting. Current cell and VOIP systems already utilise multiple compression algos.

IshKebab 8y ago

Actually if you're lucky and make a phone call with HDVoice, or whatever they're calling it, the quality is excellent. It makes a huge difference. Unfortunately the place where you really want good quality is call centres - it's often hard to hear people and half of the reason is the shitty POTS quality - and call centres will probably get HDVoice in about 40-50 years. Maybe. Edit: nm should have read all of your comment before replying!

reaperducer 8y ago
>Actually if you're lucky and make a phone call with HDVoice, or whatever they're calling it, the quality is excellent Can confirm. I spend a lot of time in fringe reception areas, but every now and then I get a good, strong signal and the HD Voice kicks in between my iPhone and my wife's and it sounds like she's standing right next to me. It really is something to experience, especially if the previous phone call was over regular tech. Back when AT&T was running the "You get what you pay for" ads to combat SPRINT and MCI, it had a service you could sign up for that would give your landline phone calls amazing quality. Sadly, a majority of people would rather pay less for crap than more for quality; even back then.
- namibj 8y ago
  Also why no one really appreciated ISDN over here in central Europe. Yes, there are ways to do better _now_, and it would have been trivial to support channels with better codecs by negotiating something different than u-law 8kHz PCM, but back then that resulted in rather good quality. The issue was that few people got ISDN phones, which resulted in them using analog outputs on an adapter device, which got later incorporated into the internet router, which at one point switched from ISDN to VoIP. And people plug a phone via an analog jacket into the router, instead of using a VoIP capable phone or even anything digital. While many do use DECT cordless phones, those rarely use the DECT hardware inside the router, and instead use the one in the charging dock, which itself connects via an analog, POTS-bandpass-filtered, phone jacket to the VoIP router. Oh well, we will probably never get that kind of quality, which is only possible with QoS on the whole path, if there is any congestion. That is the one thing something like rocket.chat and discord can't provide. Edit: the way to do this is to force quality upon people, wherever you won't drive them away with the cost this incurs. That way people will associate your brand as a whole with the quality, i.e., in that case, people will associate AT&T with quality, not AT&T premium. Normal people do not even know what kind of plan they are on, except for about one hour before and after they sign the contract.
  - gsich 8y ago
    >Also why no one really appreciated ISDN over here in central Europe. Except Germany. Which had probably the best telephone system in the world when they deployed ISDN nationwide.
    - namibj 8y ago
      I am speaking as a German. Sure, larger businesses used proper ISDN, but your uncle/mom didn't. The best you could hope for there was only DECT compression, aka ADPCM 4bit/8kHz.
      - gsich 8y ago
        Sure they did. Adoption rate was about 30%, possibly even higher at it's peak. DECT codec is useless if it's transmitted through analog lines, as it gets converted to standard 3.4k-Hz quality anyway. Except for in-house calls of course.
  - bewo001 8y ago
    The problem with land line voice quality is that people expect a land line phone / VoIP adapter to cost like 20 USD or Euro. At this price point you can't have fancy codecs and audio hardware that delivers a decent signal. Bad audio hardware with a good codec can actually decrease audio quality (the mic's noise no longer gets filtered as it is with 8kHz PCM).
- heywire 8y ago
  I think it was AT&T that had a test number you could call to hear a higher quality phone call (I was pretty young at the time, so my memory is fuzzy). I remember it sounding very good, but that test number was the only time I remember hearing that quality over the POTS. The VoLTE and HD voice I occasionally get on my iPhone reminds me of that system.
gsich 8y ago
What do you mean with "HDVoice"? On landline connections this usually means G722. G711u/a is definitly not "HD".
- namibj 8y ago
  I assume the usual wideband codecs used with VoLTE.
- IshKebab 8y ago
  I don't know what technology it is specifically, but it's a brand name they used for actual high quality calls. Think, 128 kB/s MP3, rather than the standard cups-and-string quality. It only seems to work on mobile.
  - gsich 8y ago
    I know the difference, used G722. On mobile its G722.2, a totally different codec, but with the same ~7KHz range. But there were some companies that advertised a lower frequency range as "HD".
- ahoka 8y ago
  He probably means Adaptive Multi-Rate Wideband (AMR-WB) [1], AKA G.722.2. There is a common misconception that it is VoLTE only, but actually it works pretty well on 3G too. It is night and day compared to legacy codecs. 1. https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_Wideband https://en.wikipedia.org/wiki/Adaptive_Multi-Rate_Wideband

skykooler 8y ago

I'm curious as to how fast the WaveNet decoder is? The last time I saw an article on it, it took multiple minutes to generate a second of audio.

gwern 8y ago
The original WaveNet repeated a lot of computations; with caching/dynamic programming, it became a lot faster. Other optimizations were also doable. In any case, that was eventually made moot by using model distillation to train a wide flat (not deep) NN, which is 20x realtime: https://deepmind.com/blog/high-fidelity-speech-synthesis-wavenet/ https://deepmind.com/blog/high-fidelity-speech-synthesis-wav... (This was necessary to make it cost-effective to deploy onto Google Assistant.)

dredmorbius 8y ago

Chaining codecs arbitrarily tends to create really bad artifacting. Current cell and VOIP systems already utilise multiple compression algos.