I’ve been playing with Skype lately, to further my VoIP/SIP knowledge and provide a portable way to make cheap phonecalls. I ordered Skype’s own Freetalk USB headset as its Skype-certified and forums touted Linux support. I signed up for the SkypeOut Unlimited Country plan which allows you to make unlimited calls to landlines in one country for about 3ukp per month, plus of course free Skype-to-Skype “PC” calls.
Well the first thing to do to fix the naff sound quality is remove the USB connector from the headset and just plug the two 3.5mm jacks into your soundcard – I used the front mic+headphone sockets and moved my speaker cable to the center socket, otherwise I couldn’t turn off the regular PC sounds through my monitor when making a call. That also enabled it me to use Skype4 for Windows under VirtualBox – with USB the overhead was too high I guess. So that effectively meant I could have used any PC headset, instead of one with the shortest “2.9m” cable I’ve ever seen!
One person I called thought that the older Skype 126.96.36.199 for Linux sounded better than 188.8.131.52 beta, but the main difference in sound quality seemed to come from forcing the G.711 PCMA codec to be used for SkypeOut, instead of the defaullt G.729, by inserting this line to Skype’s config.xml:
<Call> .... <ForceCodec>PCMA</ForceCodec> </Call>
I found that the much fabled SILK codec used by default in Skype-to-Skype sounded no better than PCMA in SkypeOut, I guess they’re both wideband 16KHz codecs with about 64kbps bandwidth overhead.
I also tried the Ekiga (aka GnomeMeeting) SIP provider Diamoncard, but they were more expensive and totally unusable – call quality was really bad, the SIP had no encryption (plaintext phone numbers!) and you only seemed to be able to make one call every few minutes.