[GnomeMeeting-list] Re: [Xmeeting-ohphonex] Free Software/Open Source Telephony-Summit in Germany

[Hannes Friederich <hannesf ee ethz ch>]

To everybody

Inour testing sessions at ETH Zurich with various H.323 clients, we did  
notice that H.261 video quality was good with all tested clients when  
doing point-point conferences. The MCU currently in use at ETH Zurich  
is a Radvision MCU 3. When connection to this MCU, H.261 is very bad as  
soon as there are moving frames. The problems seem to be the same as  
the developers of Codian did point out.
GnomeMeeting is also affected, so this is cleary a codec-only problem.  
GnomeMeeting 1.2 may need some patches in order to work with most  
Radvision-MCU connections unless these connections are 7.5fps CIF.
This can be done by adjusting the H.261 Capability-Settings in both  
ohphone/GnomeMeeting. I posted this a couple of weeks ago but didn't  
get any answer.

Andreas Fenkart did investigate the problem a bit more closely. I don't  
recall all details, but I think it has something to do with the used  
H.261 encoder (vic) which seems to produce only a very basic H.261.  
Perhaps Andy can give more detailed informations - he just started a  
new job at a company and is obviously very busy right now.

On behalf of the XMeeting project, we are very interested in a good  
H.261/H.263 solution which can handle all professional H.323-endpoints  
correctly.

For those interested: ohphoneX 0.3.3 will be released soon and will  
improve compaibility (e.g. re-enable calls to NetMeeting) and include a  
compatibility matrix which is supposed to be used as the start-point  
for further improvements.
The roadmap of the XMeeting project will also be updated soon.

With Best Regards

Hannes Friederich
XMeeting/ohphoneX software engineer

Am 4. Feb 2005 um 12:32 schrieb Alan Sill:

> Hi Craig and Damien,
>
> Was there ever a follow-up or wrapup session writeup, or conclusions  
> from this conference?  In testing the openh323-based/pwlib-based  
> application ohphoneX (which is otherwise regarded as a blessing by  
> this community), a study by a serious but friendly commercial MCU  
> vendor (Codian) found the following defects, as listed below.
>
> I'd like to know whether these problems are in the openh323 or pwlib  
> layers, and thus common to GnomeMeeting, for example, or specific to  
> the otherwise very nice ohphoneX implementation.
>
> Apologies to Mark Blake for quoting his e-mail without permission, but  
> I think these are things that ought to be addressed by the ohphoneX/GM  
> developers and user community and should not have to be worked around  
> by vendors:
>
> On Jan 18, 2005, at 12:03 PM, Mark Blake wrote:
>
> > Although all the endpoint manufacturers attempt to adhere to the the  
> > various standards the quality with which they manage to do so varies  
> > tremendously from manufacturer to manufacturer. For instance of “the  
> > big two” endpoint manufacturers we have seen something like 10x more  
> > bugs with one than the other. Typically these are real bugs that are  
> > not just a matter of interpretation. However there is almost always a  
> > work-around of some sort - so our code has quite a lot of stuff that  
> > attempt to detect various bugs in real time and implement  
> > work-arounds!
> >  
> >
> > In the specific case of OhphoneX we managed to find the following  
> > major bugs / issues in only about 15 minutes of testing
> >
> >
> > 1) Bad H.263 bitrate advertisment
> >
> > 2) Inability to cope with some H.261 fragmented packets
> >
> > 3) Incorrect timestamps on H.261 media
> >
> > 4) H.261 encoder only uses I-macroblocks
> >
> > 5) OhphoneX does not correctly issue fast update requests in all  
> > cases.
> >
> > So (1) is why H.263 calls do not work
> >
> > (2) is what was causing the corrupt video with H.261 but (3) would  
> > also be sufficient to cause major problems even if (2) were fixed.
> >
> > (4) is not a bug as such but means that OhphoneX is only using the  
> > most basic form of H.261 encoding which means it will need roughly  
> > 10x the bandwidth for the same quality of video compared to a “full”  
> > H.261 encoder.
> >
> > (5) means that OhphoneX has poor resilience to packet loss / bad  
> > network conditions.
> >
> >  
> > (2) and (3) are worked around in the forthcoming MCU build John  
> > previously mentioned. This is sufficient for H.261 video to work ok.
>
>
> On Jan 11, 2005, at 6:03 PM, Craig Southeren wrote:
>
> > To all,
> >
> >   The German Unix Users Group is holding the second annual Free
> > Software/Open Source Telephony-Summit n Geilenkirchen, Germany this
> > weekend and early next week. Myself and many other developers and  
> > users
> > will be attending the event. If anyone is interested in attending,
> > please see the web page at:
> >
> >   http://www.guug.de/veranstaltungen/telephony-summit-2005/
> >
> >    Craig
> >
> > ---------------------------------------------------------------------- 
> > -
> >  Craig Southeren      craigs postincrement com / craigs voxgratia org
> >
> >  Phone:  +61 243654666      ICQ: #86852844
> >  Fax:    +61 243673140      MSN: craig_southeren hotmail com
> >  Mobile: +61 417231046   Jabber: craigs jabber voxgratia org
> >
> >  Post Increment - Consulting & Services     
> > http://www.postincrement.com
> >  Vox Gratia - The Open Source VoIP portal  http://www.voxgratia.org
> >  Raving Of A Strange Mind - the VoIP blog   
> > http://www.southeren.com/blog
> >
> >
> >
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> ======================================================================
> :  Alan Sill, Texas Tech University   Office: Science 117, MS 41051  :
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