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Re: [Linphone-developers] Linphone on BlackBerry announce

From: Kristian Kielhofner
Subject: Re: [Linphone-developers] Linphone on BlackBerry announce
Date: Wed, 12 Jan 2011 13:43:07 -0500

On Wed, Jan 12, 2011 at 12:48 PM, Jehan Monnier
<address@hidden> wrote:
> As BB applications are pure java, it is nearly impossible to encode/decode 
> voice at the application level. For audio encoding, we rely on what RIM 
> provides. So far only AMR-NB is available in realtime. Today, we think the 
> best is use  "server based" transcoding. We are thinking about providing a 
> server with transcoding capabilities.

Ideally you wouldn't want to implement this server as a standalone
component because the delay and potential issues introduced by another
device proxying the RTP could have a serious impact on call quality.
Implementing transcoding to/from AMR on the final host providing the
service is no different than transcoding ilbc or anything else
(assuming you're going to G711u/a).

For the server you may want to look at Sangoma hardware transcoding boards:

They're supported by Asterisk and FreeSWITCH today (although I'm not
sure AMR-NB is available from the codec API).  I've found that
licensing and indemnifying patented codecs such as G729 and AMR isn't
really worth it in many cases.  If you were to research licensing for
a software implementation you'd find it's quite the hassle.

These boards are often cheaper than their software counterparts
(depending on volume) and offload the transcoding from the host CPU
which is a significant advantage if you intend on large call volume.

Kristian Kielhofner

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