Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Community Member

On VoFR which codec is suitable for compression

I have to configure VoFR , the host location has 2 PVC each with 16 K CIR with 56 K access link --which codec would be good default 729ar8 offers 8 K for once voice channel plus the over heads for frame which is 7 bytes and with 2 voice channels 16 K woul dbe enough.

What is the appropriate way of calculating the voice bandwidth requirement, I know one formula

required bandwidth=codec(1+overheads/payload size)..

so if this the right one, overheads are for frame then what is payload size here.

2 REPLIES
Anonymous
N/A

Re: On VoFR which codec is suitable for compression

you need to consider VAD and header compression,etc,

so for g729 with VAD and header compression, one call normally

consume about 11-12 k.

Community Member

Re: On VoFR which codec is suitable for compression

There are no header compressions on VoFR only vad can save you more bandwidth and the choice of codec and payload size on the codec ofcourse. For VOFR , a g729r8 call is a 10k compression and here is the calculation below:

Bandwidth=codec rate *[(payload_size+overhead_size)]/(payload_size)

For example for 8kbps g729:

Bandwidth=8k * (30+1+2+4)/(30)=9867pbs ~ 10kpbs

(with 30byte payload_size, 33.3 ms frame interval)

So for 2 vofr g729r8 calls you need about 20k.

Hope this helps.

116
Views
0
Helpful
2
Replies
CreatePlease to create content