March 07, 2009

HD Voice is Simpler to realize

Last month Daniel Berninger wrote a guest column expressing the benefits of using high definition codec for voice communication. In that post, Dan argues that widespread use of compatible codecs is critical. Inexplicably I had missed it when it appeared and a tweet brought it to my attention. For a long time, I have argued in these pages that we should be using wideband codecs and more specifically, I have been a proponent of Speex. But I differ with Dan in some respects and this post captures some of my thoughts.

When we decided to use a wideband codec in EnThinnai, we also faced the problem of compatibility. More importantly, we decided that our users would like to communicate with people who are not yet users of EnThinnai. Our strategy is to dynamically download the codec. I think this simple technique effectively addresses the compatibility issue.

But this means that the codec we use must be freely distributable. This is the reason we decided to use Speex. Last week Skype announced that they will make their codec widely available. I am not sure whether this kind of use is allowed.

In his post, Dan also makes a point that is not really relevant. He suggests that supporting wideband codec in PSTN will require massive overhaul of the network and so is not practical. But that is not the case. It has gone into the folklore that PSTN is not a "stupid network" and no change can be introduced at the edges. But that is not really true. Data modems and fax machines are well known examples. STU III that is designed for encrypted communication is another. So if we really want to use wideband codec and both the parties have wideband codec enabled telephones, then they can switch over to this codec, just like STU III users switch to secure mode. So let us not perpetuate the myth that PSTN is not a stupid network.

But more importantly, we should recognize that if a VoIP end-point is based on ATA, then it is "PSTN" for all practical purposes. So let us try to guide the industry to use native end-points and not ATA based. This is more critical.

Posted by aswath at 04:41 PM | Comments (3)

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