Globelabs, the innovation arm of Globe Telecom, conducted a developer training tonight at Powertips in Podium. Globe has been encouraging developers to take advantage of its test platform to come up with interesting apps. They have previously opened up API's for SMS, MMS and LBS (Location-based Services). Tonight, they announced the availability of the Voice API.
The SMS, MMS and LBS API's are very straightforward to implement. They can be accessed using standard HTTP REST (aka. name-value pair) format. For Microsoft Visual Studio-based developers, a SOAP interface is provided complete with WSDL for easy referencing. Developers are given a small quota of SMS/MMS to send/receive everyday for testing purposes. Responses are sent back in industry-standard XML.
The Voice API, however, is quite a different story. In fact, I would dare say its not much of an API. The only API-ish thing about it is the "getConsent()" part, which is similar to LBS wherein the user has to provide consent somehow that he will use it. I'm not really clear as to why this is necessary.
The rest of the "voice API" is really just standard Session Initiation Protocol (SIP). You are basically on your own to implement it (or to use open source applications like Asterisk to implement it). One concern brought up during the training is the choice of G.729 as the audio codec. G.729 is a proprietary codec that requires commercial licensing/royalty for use unlike other codecs like G.711. It has a low bandwidth requirement (8kbps, by default) though, which is why telcos favor it.
I guess I'll be doing some tinkering with this in the coming weeks.