Doug Mohney, Editor of HD Voice News is quite plain in saying that he Hates The Term “HD Audio!” In this case his comment stems from the fact that VTech, a Canadian manufacturer of consumer cordless telephones, has started to use the term “HD Audio” describe some of their latest hardware.
The company describes the “HD Audio” feature as follows:
“The frequency band has been extended allowing for the signal to be reproduced and tuned for a fuller and clearer sound.”
In addition, they seem to have implemented a kind of tone control with several preset contours.
“The equalizer feature on the handset enables you to change the audio quality of the handset to best suit your hearing. While on a call or intercom call, or listening to a message or announcement, press EQ to select the equalizer setting Treble 1, Treble 2, Bass or Natural (the default setting) for the handset. The current setting is displayed on the handset briefly.”
Since these are DECT 6.0 devices it’s possible that the cordless aspects of the system use G.722 encoded audio to provide higher quality sound for calls between handsets. However, since the device offers only the analog PSTN interface to the world it’s going to be limited to narrowband G.711 for all calls to the PSTN. The intercom function may be improved, but it’ll have limited impact upon most of the things that people do with a telephone.
On this basis VTech can rightfully claim to have made some effort at improved audio quality, even if it might be of limited utility to most people.
I wonder if all of this is really just an artifact of the fact that they are using a recent DECT chipset? Current DECT silicon doubtless implements some basic wideband functionality over the DECT link, even if the overall design of the product is not able to leverage it broadly.
The bigger question is really defining HDVoice in a manner that doesn’t confuse the customer. The term “HD” is used so widely as to be essentially meaningless. There had been some hope that the group of companies behind the HD Connect effort would arrive at some standard definition of HDVoice.
Is anything beyond the 300 Hz – 3400 Hz passband of G.711 considered HDVoice? Or is that baseline the 50 Hz to 7KHz passband of G.722 the baseline? I would think that later to be the case.
Where it gets vague is where DSP-based trickery is used to “frequency extend” a narrowband PSTN call. That is, can someone through some special processing extrapolate high-frequency detail from a G.711 call? I’ve talked to some chipmakers who say it can be done. I’ve also heard that it can sound bad. Examples of this have been difficult to find.
In general, I think I must agree with Doug, the term “HD Audio” is unfortunate & confusing when used to describe a device that cannot make a bone fide wideband call.
P.P.S. – The term “Polycom HDVoice” is a Polycom trademark.