Hi Christian and others
Timescaling and jitter buffer management is AFAIK not included in the codec
specifications done in other standards foras. But that does not mean that it is
left unspecified. In 3GPP TS we settled with a specification of only the
requirements
http://www.3gpp.org/ftp/Specs/archive/26_series/26.114/26114-910.zip
There are many reasons to why we did this, one is that we regard time scaling
as yet another pre/post processing algo like packet loss concealment, echo
cancellation or noise suppression, and the hard cold truth is that the less one
need to specify in terms of code so much the better (go figure..). We needed
however to set some requirements however to avoid poor implementations.
With the above in mind I would claim that it is wrong to state that the answer
to statement 2) below is a NO.
/Ingemar
From: "Christian Hoene" <hoene at uni-tuebingen.de>
To: "'Xavier Marjou'" <xavier.marjou at orange-ftgroup.com>
Cc: 'IAB IAB' <iab at iab.org>, codec at ietf.org, 'IETF Discussion' <ietf at
ietf.org>, 'IESG IESG' <iesg at ietf.org>
Date: Tue, 12 Jan 2010 01:27:43 +0100
In-reply-to: <458913681001111218o3b232e4sd785b3c09809fcbc at mail.gmail.com>
References: <20091223171501.7BAE33A697D at core3.amsl.com>
<13194D66-2110-4CB2-B130-8807BE57488B at cisco.com>
<458913681001111218o3b232e4sd785b3c09809fcbc at mail.gmail.com>
--------------------------------------------------------------------------------
Snip snip...
Therefore, the 3 stages mentionned are essential to be run
sequentially:
"(1) get consensus on the requirements, (2) see if an existing codec
meets the requirements, and (3) specify a new codec only if none are
found in stage 2. Initially the WG would be chartered for (1) and when
that was done it would be re-charted for (2) and so on. "
Obviously, the current requirements document does contain features which are
not supported by today's standardized codecs. As an example, take time
stretching and time compression. Thus, everybody following the discussion
must come to the conclusion that (2) has been answered with no.
=================================
INGEMAR JOHANSSON M.Sc.
Senior Research Engineer
Ericsson AB
Multimedia Technologies
Labratoriegränd 11
971 28, Luleå, Sweden
Phone +46-1071 43042
SMS/MMS +46-73 078 3289
ingemar(_dot_)s(_dot_)johansson(_at_)ericsson(_dot_)com
www.ericsson.com
Visit http://labs.ericsson.com !
=================================
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