Has anyone implemented a video-capable SIP-H.323 gateway using free, open-source software?
If so, please comment.
Asterisk, FreeSWITCH and YATE all have some ability to connect SIP and H.323 endpoints to one another. Asterisk acts as a back-to-back user agent (B2BUA) and the other two act as proxies. All can switch audio calls. Video seems to be another story.
In theory, it should be straightforward. The difficult part is translating the signaling; the media streams are the same. Thus the interworking component (PBX, switch, or proxy) should be able to translate signaling and then proxy the media between the endpoints. If video is just another media stream, why doesn’t it work just the same as an audio-only call?
I’ve tested YATE (built-in modules), Asterisk’s chan_ooh323, a custom chan_ooh323 for Asterisk 1.4 that specifically enables video (but crashes/disconnects, and is definitely not supported unless you buy the unnamed company’s video IVR product, which I haven’t), FreeSWITCH’s mod_h323 and mod_opal. I never really got the FreeSWITCH mods working stably. YATE and Asterisk worked fine in audio mode. Neither would translate video (H.263 protocol, nothing fancy).
Additional reading: RFC 4123, Session Initiation Protocol (SIP)-H.323 Interworking Requirements