2009/11/11 mylen <mylen at sina.com>: > Hi all: > I'm confused with VAS and VAS-Direct,do they all support G.729? I'v read > http://trac.pjsip.org/repos/wiki/Nokia_APS_VAS_Direct and > http://trac.pjsip.org/repos/wiki/VAS ,it said VAS-Direct use switch board > and passthrough codec,so VAS-Direct dosn't support conference, does it mean > VAS use traditional conference framework like normal codec? and > What's the difference between VAS and VAS-Direct? > In non-"Direct" setup, pjsip has sound device, conference bridge, and software codecs (like Speex. GSM, etc.). So no, we don't support G.729 in non-Direct setup since we don't have G.729 software codec. The xxx-Direct feature was developed to support hardware codecs that sound devices have, such as G.729, AMR NB, iLBC, etc in VAS/APS. Since the audio from/to the sound device is already in encoded format, we don't need to encode/decode the audio with the usual software codecs anymore, that's why we invented passthough codecs, which basically just provide the codec info for SDP, and doesn't do any real encoding/decoding. Also because audio is encoded, we can't use the conference bridge anymore, since we can't mix encoded audio. Hence the switchboard. But even when xxx-Direct is used, you can still enable/use software codecs if you want to, such as Speex and GSM, since these codecs are not supported by the devices. When this codec is selected for the call, PJSUA-LIB will take care that VAS/APS is opened in the correct mode (i.e. PCM) to handle this. But you still loose the conferencing feature since the switchboard instead of conference bridge is used (the selection between switchboard and confbridge is done at compile-time rather than run-time). Hope this helps. Let me know if you still have any more doubts. Cheers Benny
