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

[Alan Sill <Alan Sill ttu edu>]

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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