Recording VOIP Phones

[dabble]

I have a 911 center, with a CS1000E at Rls 7.0 and am using M3904 sets for incoming 911 calls.

These M3904 sets are connected to a voice logger (Comm Logger from CVDS model NP192).

I also have two 1230 VOIP sets, that are programmed the same as the M3904 sets as far as the 911 lines goes and I would like to record the VOIP sets.

Apparently I need to access the RTP packets of the VOIP phones and the RTP's needs to use G711 or G729.

I have checked the CS1000E system to see what codec is being used and both G711 and G729 are checked off within UCM and the codecs.

So, does anyone know how I would access the RTP packets of the VOIP phones?

I asked my internal network folks and they suggested I change them to M3904, which really isn't an option.

Thanks.

 

[3Sixty]

Why is the codec relevant for recording calls?

When you say recording the calls do you want to record the conversation or the packets going between the phones and the CS1000?

Most IP based call records support the common codecs G729 and G711.

Thanks,
Colin

http://www.3sixtynetworks.com

 

[dabble]

We want to be able to record the entire conversation since it is a 911 call.

Not sure why the codec is needed - it was something the vendor mentioned.

Thanks.

 

[bad69cat]

The G.711 codec requires a connection almost 3 times faster than that required by the G.729 codec, so to get the analog converions for recording you need to know which one you are using at the time the call is in progress to get the correct data rate. I think you would need something that can differntiate or convert either way to get consitant results...?

 

[TelecomGuyUT]

Hi dabble,

Depending on the firmware that you have on your phones, you can implement DSCP to tag packets and then use duplicate media streaming to record calls to and from IP phones.

And yes, depending on the codec(s) used that can eat up a lot of bandwidth. (which is why your network guys would rather have you make them 3904s...)

 

[3Sixty]

The codec provides call quality not speed. The G711 codec is a 64kb codec the same as an ISDN call. The G729 codec without VAD is a 8KB codec lower quality, The G711 codec uses less processing power to compress and has a shorter time delay. The G729 codec requires more processing power takes longer to compress and adds delay to the entire packet and requires additional jitter configuration. To the naked ear the call quality would be hard to tell the difference but when you are call recording the loss tends to create volume loss etc.

I would recomend the G711 codec unless bandwidth is at a premium.

You can force the phone to use a codec on the CS1000 and like I said I would recomend G711 for call quality. Bandwidth including ethernet overheads etc it is about 126k per call with 10ms payload to reduce delay.

G729 as stated above is closer to 35k per call.

This is a link to a bandwidth calculator. There is alot of these around some simple some more complicated.

http://www.bandcalc.com/

Thanks,
Colin

http://www.3sixtynetworks.com

 

[3Sixty]

To use the DSCP you would also require Layer 3 switches.

Thanks,
Colin

http://www.3sixtynetworks.com