Subject: RE: [AVT] Audio/Video and packet loss

From: "Verma, Atul" <[email-masked]>
Date: Fri, 21 Apr 2006 13:52:02 -0500

I think it depends upon the application. For example, in Video Telephony
(where there is not much motion), if we are talking about packet loss
then I would think Audio is more affected than Video. Loss of Audio
packets will cause severe degradation in perceived voice quality whereas
the user may not even realize the loss of several video packets

Atul Verma
Texas Instruments Inc

-----Original Message-----
From: Dave Singer [mailto:[email-masked]] 
Sent: Friday, April 21, 2006 2:34 PM
To: Alejandro Cabrera Obed; AVT Lista
Subject: Re: [AVT] Audio/Video and packet loss

At 14:42  -0300 21/04/06, Alejandro Cabrera Obed wrote:
>Hi people, I have a brief question....
>
>In general, which type of media flow (audio or video) is more 
>affected with packet loss in an IP network ???
>
>Is this just dependant on the CODEC algorithm used by the audio or 
>video or maybe there is a media that is more sensitive for any given 
>reason ???

In general, video tends to be more affected than audio.  The reason 
is that audio tends to encode each time-interval independently, or 
almost so (AAC, for example, needs two consecutive frames for the 
second to be *perfectly* decoded), whereas in video, extensive 
frame-differencing is usually done ('motion estimation' and so on). 
That means that an error affects not only the frame for which data 
was lost, but also any frame which predicts from the incorrect 
portion of that frame.  This causes 'ghosting' and other artifacts 
that can persist for some time (until those regions are painted again 
with correct data).  The affect can be mitigated but not eliminated 
by estimating what was lost, and so on.

Hope this helps
-- 
David Singer
Apple Computer/QuickTime

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt