H.323 Vs SIP VoIP & Softphone Vs Hardphone

Archived from groups: comp.dcom.voice-over-ip (More info?)

> I would like to know that is there any difference in voice quality over
> ADSL 256kbps connection while using H.323 or SIP , would like to know
> which is better for VOIP communication on low bandwidth,which give
> better compression , less echo and good quality .

Neither protocol has something to do with echo or voice quality. Both SIP
and H.323 are signalling protocols which are used only to establish media
channels. Those in turn are transmitted via RTP in both cases, so there
shouldn't be a difference in quality between SIP or H.323 devices.

> Also would like to know that is there a difference in voice quality and
> echo while using hardphone than a softphone . Which from both gives
> better sound quality and less echo on low bandwidth .

In theory there's no difference between a "hard"phone and a softphone. In
practice most "tangible" VoIP phones include a real DSP doing some echo
cancellation. With next to all Softphones echo cancellation is pretty
uncommon, so you get better quality with a hardphone here.