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Is it possible to convert G729 packet size ?

Hi

Is it possible to convert g729 codec packet sizes in IP-to-IP gw or any other device? IE:

G729 20 ms---To---G729 100ms

Deniz

6 REPLIES

Re: Is it possible to convert G729 packet size ?

Deniz,

Yes, it's possible. It's done with the "codec" command on a per dial peer basis. Please see the following link for command syntax as well as valid payload sizes for different codecs. Be aware that as you increase the payload size, the effect of each dropped packet on voice quality becomes greater.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_chapter09186a0080080c99.html#wp1054445

Hope this helps. If so, please rate the post.

Brandon

New Member

Re: Is it possible to convert G729 packet size ?

Dear Brandon

Ok i already know that, but what i am asking is i have an incoming voip call which is G729 20ms and i want to convert it with an ip-to-ip gw to G729 100ms call and than insert my voip backbone. Can i do that with ip-to-ip gw or any other device?

Best Regards,

New Member

Re: Is it possible to convert G729 packet size ?

Unfortunately, you run into the same problem that exists when trying to convert codecs. What you want can be done, but not currently with IPIPGW. Even within this people persist in trying to run 10 or 20 byte payloads to 'improve' quality. In many cases the increased packet load simply overwhelms the network at some point.

Yes it is true a smaller payload would give better quality in a perfect network with some loss. Unfortunately, the world does not work like the lab. By increasing the payload size, you reduce bandwidth and significantly reduce packet rate, the latter being what kills most router interconnects.

See my rant from 04 http://blog.webvoip.com/blogs/spade/index.php?m=20040709

ANYway, it would be nice to do this, but while codec is negotiated, payload is usually not and must be set by both ends to avoid asymetrical usage. Conceptually, I think IPIPGW could do something of this sort without the major CPU overhead associated with a codec transcode. It would require some extra work however, because it would require the router to buffer and combine packets one way, then split packets the other way. This would add an amount of latency at least as much as the change, in your case 100-20ms. Other issues might be packet sequence reordering. Sounds possible, but then imagine 500 calls simultaneous.

So, great idea that we all would love to see, but unlikely. Bandwidth is much cheaper now, and router CPUs are getting faster, so it may all become moot.

John Spade

webVoIP

New Member

Re: Is it possible to convert G729 packet size ?

Bandwitdth is cheaper but not the international ones:) Yes when you think internal international backbone of a telecom company 20-100 ms convertion makes half of the bandwidth which in 2000 concurrent calls it really makes difference. Thanks anyway.

Deniz Pecel

New Member

Re: Is it possible to convert G729 packet size ?

Granted, but by cheaper I mean an international 256K is no longer $40,000/month. Your best recourse it to try and get your providers to send a larger payload. They may not be willing to do 100, but they probably can do 40. Remember to set incoming peers and classes on your remote end.

John Spade

webVoIP

New Member

Re: Is it possible to convert G729 packet size ?

Hi,

As far as I know, with DSP in IPIPGW you convert certaion type of codecs.But I am not sure can you convert the packet size.If you have DSP in your IPIPGW you can try.

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