Re: [codec] #6: Echo and Ultra-low Delay

["codec issue tracker" <[e-mail]>]

#6: Echo and Ultra-low Delay
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 Reporter:  hoene@…                 |       Owner:     
     Type:  defect                  |      Status:  new
 Priority:  major                   |   Milestone:     
Component:  requirements            |     Version:     
 Severity:  Active WG Document      |    Keywords:     
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Comment(by hoene@…):

 [Benjamin]:

 In the presence of echo, round-trip delay must be kept below 30 ms to
 ensure that the echo is perceived as sidetone, according to the Springer
 handbook of speech processing:

 (http://books.google.com/books?id=Slg10ekZBkAC&lpg=PA83&ots=wc9yM9WrCs&dq=sidetone%20delay%2030%20ms&lr&pg=PA84#v=onepage&q&f=false)

 [Stephen]: VOIP phones that are capable of speakerphone operation all have
 acoustic echo cancelers, and those cancelers are already tuned to deal
 with internet delays with other voice codecs.  Certainly our phones and
 videoconferencing systems do not have problems with path delays of this
 order (hundreds of milliseconds).

 Such low delays are clearly impossible on many paths, but for Boston to
 New York City (or London to Paris), ping times can be less than 18 ms,
 making echo->sidetone conversion just barely possible for a codec with 5ms
 frames.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/codec/trac/ticket/6#comment:1>
codec <http://tools.ietf.org/codec/>