As a result of last week’s announcement of Skype’s selection of VSNL as a call termination partner, I have spoken with Scott Bagby, Skype’s Vice-President of New Markets, about why they entered into this agreement; our discussion quickly transitioned to one about Skype’s ongoing efforts to improve SkypeOut call quality.
Scott pointed out that many factors enter into the final call quality:
Getting to the Internet: The audio hardware, PC configuration (especially active programs) and the nature of the Internet connection can all impact call quality even before reaching the Internet. Note that these are factors that, while Skype can make recommendations, are out of their ultimate control. This also explains one benefit of PC-Free phones; they are not competing with any other program for processor cycles.
Once at the Internet, SkypeOut calls go forward to call termination providers for which there are two general categories:
- Aggregators who aggregate various services around the world to complete a connection
- Local terminators who provide country-specific termination services
Skype initially contracted with five aggregators worldwide with the thinking that this would give the broadest coverage to a maximum number of countries with a minimum account management overhead. However, calls via aggregators can be routed through multiple carriers, a factor over which Skype has no control. Skype found a high variability in call quality placed through aggregators. Fundamentally a call could go across several "hops" with a need to unpackage/repackage (decode/recode) the voice signal at each hop, increasing the potential for call quality degradation.
As a result Skype has started signing agreements with country-specific call termination services, for countries such as, for example, Germany, Sweden and Brazil. Through their agreement with VSNL, they are able to add Canada and India to this list. Recall that VSNL acquired Canadian-based Teleglobe for their international VoIP expertise. As these calls go directly from Skype’s gateway to the local country, it is anticipated that through these agreements SkypeOut call quality can, over time, be improved on a country-by-country basis. Yet there will always be a need for the aggregators in order to maintain and ensure worldwide coverage.
How does Skype measure call quality? A key input is the feedback provided by users. Remember those "how was your call?" web screens that would occasionally pop up after finishing a SkypeOut call? These call quality questions are now supposed to be popping up within the Skype client as one feature upgrade of Skype 3.2. Skype knows the routing for each specific call and combines that with the feedback from a call to determine call quality patterns and set priorities for where improvements in call quality are needed.
Another contributor to variable call quality is the coding/decoding that occurs with wireless voice streams; combined with the lower audio bandwidth of wireless phones, this requirement results in an additional weak point where call quality can degrade.
While I have not had many problems with SkypeOut calls (and then mostly on calls to mobile phones), we can only hope that Skype, in its termination agreements, can pick the winners when it comes to managing call quality.
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