[Asterisk-Users] Asterisk Codecs [G.729]

[Low, Adam]

I posted the results of my real world analysis of codec bandwidth usage on this list a couple of weeks back. Here's the table I put together and an example of calculating bandwidth over ADSL.

G.711 over Ethernet 	= 95 Kbps per channel
G.711 over IP/PPP		= 86 Kbps per channel
G.711 over ADSL/ATM	= 108 Kbps per channel

G.729 over Ethernet	= 39 Kbps per channel
G.729 over IP/PPP		= 30 Kbps per channel
G.729 over ADSL/ATM	= 45 Kbps per channel


200 bytes G.711 packet + 8 bytes AAL5 overhead = 208 bytes
208 bytes fit in 5 cells of 48 bytes payload
5 cells are 265 bytes. VoIP over ATM AAL5MUX thus has an overhead of 21.51%
VoIP G.711 conversation sends 50 packets per second.  This uses 250 cells per second.
This causes approximately 10 OAM5 cells to be sent over the duration.

The total bitrate is thus (250 + 10) * 53 bytes * 8 bits = 110240 bits/second = 107.66Kbit/s


-----Original Message-----
From: Rich Adamson
To: asterisk-users at lists.digium.com
Sent: 10-3-04 12:41
Subject: Re: [Asterisk-Users] Asterisk Codecs [G.729]

All of the numbers he's showing are apparently adding inbound and
outbound
traffic together, giving results that are approximately double what is
actually seen on the wire. If he is working in a half-duplex ethernet
environment, those numbers have some meaning; if full-duplex, then cut
them
in half for reasonable engineering values. (Also, some _appear_ to be
questionable.)


> What is the method you are using to test the bandwidth. Can you give
us a outline 
> how to do a bit rate measurement on
> asterisk.
> 
<snip>
>      
>     ulaw 64 Kbps, sample-based Also known as alaw/ulaw 166kbits/sec
>     alaw 64 Kbps, sample-based Also known as alaw/ulaw 167kbits/sec
>     gsm 13 Kbps (full rate), 20ms frame size   66kbits/sec
>     speex 2.15 to 44.2 Kbps     n/a
>     iLBC 15Kbps,20ms frame size: 13.3 Kbps, 30ms frame size
57.6kbits/sec
>     G.729 8 Kbps, 10ms frame size    license
>      
>     Have anyone test it with G.729?  Please let me know.


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