Re: [codec] #16: Multicast?

["Christian Hoene" <[e-mail]>]

Hi,

I will ask the ITU-T SG12 chair and the authors, whether we can make those documents public.

With best regards,

 Christian


---------------------------------------------------------------
Dr.-Ing. Christian Hoene
Interactive Communication Systems (ICS), University of Tübingen 
Sand 13, 72076 Tübingen, Germany, Phone [phone] 
http://www.net.uni-tuebingen.de/


>-----Original Message-----
>From: Marshall Eubanks [mailto:[e-mail]]
>Sent: Tuesday, May 11, 2010 6:48 PM
>To: Ben Schwartz
>Cc: Christian Hoene; [e-mail]
>Subject: Re: [codec] #16: Multicast?
>
>
>On May 11, 2010, at 12:30 PM, Ben Schwartz wrote:
>
>> On Tue, 2010-05-11 at 16:38 +0200, Christian Hoene wrote:
>>> Until 400ms quality is still acceptable (about toll quality). The
>>> ITU-T G.107 quality model reflects this opinion.
>>>
>>> However, in the recent years, new results have shown that the impact
>>> of delay on conversation quality is NOT as strong as assumed.
>>
>> I have been unable to locate the paper that is the source of these
>> claims.  However, I will note that
>>
>
>As a point of order, I object to any graphs without an available paper
>behind them.
>
>> (1) The results conflict with common sense.  A round-trip delay of 800
>> ms makes normal conversation extremely irritating in practice.  I'm
>> not
>> surprised these results don't show up in laboratory tests, because
>> fast
>> conversations with interjections and rapid responses typically
>> require a
>> social context not available in a lab test.
>>
>
>This depends a lot on what sort of discussion is at issue (and, also
>on the culture of the participants).
>
>For example, in my experience telepresence sessions tend to be
>structured meetings and can typically tolerate even half second delays
>without too much disruption, while for a one-on-one conversation on
>the same equipment the same delay can be pretty objectionable.
>
>Having said that, I myself also find the previously attached graphs a
>little odd, and want to see a written description of just what sort of
>experiments they describe.
>
>> It's possible that the ITU regards "extremely irritating" as
>> "acceptable", since effective conversation is still possible.  In that
>> case, I would say that the working group intends to enable
>> applications
>> with much better than "acceptable" quality.
>>
>> (2) Tests may have been done in G.711 narrowband, which introduces its
>> own intelligibility problems and reduces quality expectation.  Higher
>> fidelity makes latency more apparent.  Similarly, the equipment used
>> may
>> have introduced quality impairments that make the delay merely one
>> problem among many.
>
>Again, without the papers behind them, we are wasting our time having
>such discussions.
>
>Regards
>Marshall
>
>P.S. This thread has wandered far from multicast...
>
>
>>
>> (3) I presume the tests were done with careful equipment setup to
>> avoid
>> echo.  The perceived quality impact of echo at 200 ms one-way delay is
>> enormous, as shown in
>>
>> http://downloads.hindawi.com/journals/asp/2008/185248.pdf
>>
>> Using an echo-canceller impairs quality significantly.  Imperfect echo
>> cancellation leaves some residual artifact, which is also irritating
>> at
>> long delays.
>>
>> The tests (even in the paper above) were performed using a telephone
>> handset and earpiece.  High-quality telephony with a freestanding
>> speaker instead of an earpiece demands especially low delay due to the
>> difficulties with echo cancellation.
>>
>> --Ben
>>
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