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PCMU/PCMA (G.711μ and G.711a) are not original landline quality audio, but rather what Bell Systems felt they could get away with passing off as a toll quality

by posguy 6y ago

PCMU/PCMA (G.711μ and G.711a) are not original landline quality audio, but rather what Bell Systems felt they could get away with passing off as a toll quality call in 1972. Lyra will likely sound better, but the reproduction accuracy is apt to be quite a bit poorer as many others have commented. G.711 was created to require nearly no processing (its nearly raw PCM data from a sound card after all) while operating at reasonable bitrates, Lyra looks much more computationally intensive and will likely only run on smartphones in the next few years. Edit: Is Lyra a significant improvement over modern Opus at 8Kbps? You can buy a Grandstream HT802 analog telephone adapter for ~$30 and its DSP can decode Opus today, whereas Lyra will require orders of magnitude more power to decode while providing much worse reproduction accuracy.

nl 6y ago
> Is Lyra a significant improvement over modern Opus at 8Kbps? It is over 6Kbps Opus[1]. > You can buy a Grandstream HT802 analog telephone adapter for ~$30 and its DSP can decode Opus today A RaspberryPi Zero will provide more than sufficient power for Lyra (it was originally implemented on a Pixel 2). That's ~$10 [1] https://www.cnx-software.com/2021/02/28/lyra-audio-codec-enables-3-kbps-bitrate-for-high-quality-voice-calls/ https://www.cnx-software.com/2021/02/28/lyra-audio-codec-ena...
- deleted 6y ago
  [deleted]
- posguy 6y ago
  > It is over 6Kbps Opus[1]. The overhead from packet headers to send data every 40ms is 9.6kbps, is the difference between 12.6Kbps and 17.6Kbps meaningful at that point? We are sending the same number of packets, likely with the same packet loss rate. > A RaspberryPi Zero will provide more than sufficient power for Lyra A Raspberry Pi Zero can't run Lyra, as the proprietary math kernel is only offered in compiled form for x86-64 and android-arm64: https://github.com/google/lyra#license https://github.com/google/lyra#license
  - nl 6y ago
    > is the difference between 12.6Kbps and 17.6Kbps meaningful at that point It is when you are sending video as well. One of the stated purposes of this work is to enable video conferencing over 56Kbps dial up modems. > A Raspberry Pi Zero can't run Lyra, as the proprietary math kernel is only offered in compiled form for x86-64 and android-arm64 How annoying! Still - the point is that hardware capability isn't likely to be the issue.
    - miohtama 6y ago
      It is mentioned in other comments that the math kernel will be opened.
- walrus01 6y ago
  > > You can buy a Grandstream HT802 analog telephone adapter for ~$30 and its DSP can decode Opus today almost entirely irrelevant if you're making calls to or from the PSTN, since your SIP trunking provider most likely only supports G.711 alaw/ulaw, or even if they support you handing them a call as G.722 or any other codec, their upstreams almost certainly don't support anything other than G.711.
- sgerenser 6y ago
  Isn’t the Pixel 2 much more powerful than a Raspi Zero?

by posguy 6y ago

nl 6y ago

> Is Lyra a significant improvement over modern Opus at 8Kbps? It is over 6Kbps Opus[1]. > You can buy a Grandstream HT802 analog telephone adapter for ~$30 and its DSP can decode Opus today A RaspberryPi Zero will provide more than sufficient power for Lyra (it was originally implemented on a Pixel 2). That's ~$10 [1] https://www.cnx-software.com/2021/02/28/lyra-audio-codec-enables-3-kbps-bitrate-for-high-quality-voice-calls/ https://www.cnx-software.com/2021/02/28/lyra-audio-codec-ena...

deleted 6y ago
[deleted]
posguy 6y ago
> It is over 6Kbps Opus[1]. The overhead from packet headers to send data every 40ms is 9.6kbps, is the difference between 12.6Kbps and 17.6Kbps meaningful at that point? We are sending the same number of packets, likely with the same packet loss rate. > A RaspberryPi Zero will provide more than sufficient power for Lyra A Raspberry Pi Zero can't run Lyra, as the proprietary math kernel is only offered in compiled form for x86-64 and android-arm64: https://github.com/google/lyra#license https://github.com/google/lyra#license
- nl 6y ago
  > is the difference between 12.6Kbps and 17.6Kbps meaningful at that point It is when you are sending video as well. One of the stated purposes of this work is to enable video conferencing over 56Kbps dial up modems. > A Raspberry Pi Zero can't run Lyra, as the proprietary math kernel is only offered in compiled form for x86-64 and android-arm64 How annoying! Still - the point is that hardware capability isn't likely to be the issue.
  - miohtama 6y ago
    It is mentioned in other comments that the math kernel will be opened.
walrus01 6y ago
> > You can buy a Grandstream HT802 analog telephone adapter for ~$30 and its DSP can decode Opus today almost entirely irrelevant if you're making calls to or from the PSTN, since your SIP trunking provider most likely only supports G.711 alaw/ulaw, or even if they support you handing them a call as G.722 or any other codec, their upstreams almost certainly don't support anything other than G.711.
sgerenser 6y ago
Isn’t the Pixel 2 much more powerful than a Raspi Zero?