Unity Codec and Audio Quality

[williams.jeff]

Sorry for beating a dead horse (I've looked thought the archives for this and read quite a bit), but I want to make sure I'm doing 'The Right Thing'.

We currently have Unity 4.0.3 VM only with CCM 3.3(4) in a centralized WAN deployment. The majority of users are WAN based, so they hit Unity as g.729. Our Unity was installed with g.711 as the default codec. I have had many complaints that the voice mail audio quality is never good (most common complaints are 'scratchy' or 'cell phone-like' or 'underwater'). I recently changed my phone's config so I hit via 729 and I have to say it isn't great. It isn't horrible, either, but prior to that I used 711 and it was perfect. Has anybody else run in to this?

Would I gain ground on the quality issue by changing the default codec to 729? What is the best practice for this type of installation?

TIA,

Jeff

[mrmccann]

A phone call using G729 is not going to sound as good as a phone call using G711. G729 is a lower bit-rate codec.

That said, there could be a couple issues that are making the G729 calls sound worse, so you might want to investigate those. Check out this document for more info:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_tech_note09186a00801663a2.shtml

If most of your phone calls are coming in as G729, you probably want to avoid transcoding on the Unity server as much as possible, which would mean getting all the prompts, wav files, etc over to G729, as well as changing message storage format to G729. Check out this link if you haven't already:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_upgrade_guides_chapter09186a008022dfc2.html#wp1048893

One other note, if you are using a packetization interval other than 20 ms for your G729 calls - we did have a defect that made voice quality on those calls worse - see CSCed52913. If you upgrade to TSP 8.0(1) you'll get this fix.

I don't think the move to G729 alone will improve your audio quality problems, however you never know.