[Freeswitch-users] Sample rate and recordFile

[David Knell]

- plus UDP/RTP overhead.  Budget 10 calls/megabit for G.711 and you'll
have a bit of headroom available.

--Dave

> Most calls are at 8kHz. The formula for bandwidth is sampling rate *
> bit rate * channels, so 8000 * 8 * 1 = 64000 = 64kbps (per way).
> 
> 
> Math
> 
> On 18-Jun-09, at 1:01 PM, Andy wrote:
> 
> > Thanks Brian, 
> >  
> > So, just to calrify will the base call always be 8kHz? 
> >  
> > On a related note, do you happen to know the bitrate of each open
> > channel/live call? Is it 16 kilobits per second like the recorded
> > audio? I need to do some calculations on the badwidth required to
> > handle a certain number of concurrent calls.
> >  
> > Many thanks
> > Andy
> > 
> > 
> > ____________________________________________________________________
> > From: freeswitch-users-bounces at lists.freeswitch.org
> > [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of
> > Brian West
> > Sent: 18 June 2009 18:11
> > To: freeswitch-users at lists.freeswitch.org
> > Subject: Re: [Freeswitch-users] Sample rate and recordFile
> > 
> > 
> > 
> > 
> > On Jun 18, 2009, at 11:54 AM, Andy wrote:
> > 
> > > 1) I notice that when I change the sample rate it automatically
> > > changes the bit rate too. I understand why this is the case but
> > > wondered if it was just as easy to be able to control the bitrate
> > > as well as the sample rate.
> > 
> > 
> > If you're talking about mod_shout, NO.  You'll end up picking an
> > invalid bitrate and asking why it doesn't work... been there done
> > that... I changed it a few months back to pick the optimal bitrate
> > for the sample rate.
> > 
> > > 2) When I use a sample rate other than 8000 I get a warning
> > > 'Sample rate doesn't match'. I guess this puts some extra load on
> > > the server. If all my calls are being recorded and all at 11025
> > > can/should I alter the sample rate of the base call to 11025?
> > 
> > NO.  Your phone call is running at 8kHz, Your sound file is 11025
> > and they don't match, If you were to play this file into an 8k
> > channel without a resample it would sound a little like satan.  or a
> > dragging tape deck.  The file has to be resampled to match the
> > current session rate. 
> > 
> > 
> > /b
> > 
> > 
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> 
> 
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-- 
David Knell, Director, 3C Limited
T: +44 20 3298 2000
E: dave at 3c.co.uk
W: http://www.3c.co.uk