Ask Mr. Andrews: What is HD Voice?

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• Actually, the term "HDVoice" is a Polycom trademark. The generic term is "wideband telephony."

  It's also worth noting that lesser IP phones, like the Grandstream line, may support G.722. However, the benefits are only realized when using a headset. The built-in transducers are not up to the task.

• @ Michael:

  We totally agree (I think Cory noted that HD Voice was an industry marketing term..sort of that Kleenex/tissue scenario).

  I have never personally done G.722 on a Grandstream phone, however, there newer models have made some solid leaps and I wouldn't be surprised if there have been upgrades in this department.

• Another great post, Mr. Andrews! As you may have heard, we at VoIP Users Conference are doing a test of wideband conferencing on Friday Nov 7th at Noon EST.
  I've tested G.722 on eyeBeam, Polycom 650 and Siemens S675IP. The most marked difference is on the Polycom, but then their audio is already very good, as you all know.

• @Randulo:

  Very nice..it would be interesting to have the conference in both wideband and normal codec and somehow splice the two together after in order to hear the difference.

• I believe, please correct me if I am wrong, but HD is only effective when you are speaking with another HD user.

• Michael - you are correct, all participants in an HD calls must have an HD compatible endpoint device or softphone. The aforementioned hardware phones support HD, and we recently uncovered a SIP softphone that support G.722 wideband audio codec as well. It's called QuteCom and you can find it here http://www.qutecom.org/

• Well counterpath's X-Lite (and its siblings bria and eyebeam) support wideband codecs though not G.722. It supports Broadvoice-32 and Broadvoice-32 FEC

  And to be honest Using X-Lite (soft-phone) with our in house Asterisks server has been one hell of a combination and the quality of the sound really is magnificent. Combine that with the Data draw being minimal compared to a few other soft phones we have tried.

• At ZipDX, we are very committed to wideband audio as a critical enhancement to conference calls, where the enhanced fidelity really helps in recognizing voices, understanding accented speakers, and distinguishing al those consonants that get muffled in narrowband and result in endless "could you repeat that?" requests. The net, as noted by Cory, is greatly reduced fatigue (especially on those marathon calls) and more brainpower focused on the business at hand.

  Add Avaya (one-X) and Shoretel to the list of vendors building wideband-capable phones. Audiocodes also just announced wideband phones.

  "Both ends" do indeed need to be wideband-capable to get the full benefit. At ZipDX, we support conference calls with a mix of wideband and narrowband participants. The widebanders will hear each other in wideband. The quality difference is quite obvious if you connect in wideband and then listen to the contrast between two other participants, one in wideband and another in narrowband.

  "Polycom HD Voice" is a Polycom trademark, but I think we can all say "HD Voice" and get away with it.

• I would like to know the best codec to be used at brazil, we have a poor dsl quality, sometimes it is lower than 30k of up load, is there softphones or ATAS to be used at dialed internet conection or lower sppeed? thank you

  send suggestions to heliovomachado@hotmail.com

  • Helio, you'll most likely want to be using G.729, as it offers the best compression.

    Teracall has the table which shows how the codec's theoretical bandwidth usage expands with UDP/IP headers:

    Codec BR NEB
    G.711 64 Kbps 87.2 Kbps
    G.729 8 Kbps 31.2 Kbps
    G.723.1 6.4 Kbps 21.9 Kbps
    G.723.1 5.3 Kbps 20.8 Kbps
    G.726 32 Kbps 55.2 Kbps
    G.726 24 Kbps 47.2 Kbps
    G.728 16 Kbps 31.5 Kbps
    iLBC 15 Kbps 27.7 Kbps

    BR = Bit rate
    NEB = Nominal Ethernet Bandwidth (one direction)