Does Anyone Prefer the Voice Quality of G.729a Over G.711?

[ctylor]

I've seen some conflicting reports on this forum and others over the results of using G.729 as their preferred/primary voice codec instead of G.711u, even in cases when it seems like the person should have the 95+ kbps upload capacity to support G.711. I wanted to draw this out in its own topic.

Does anyone here use G.729a/b as a preferred codec not only because they must due to bandwidth constraints, but because they also just get better results qualitatively from using it instead of using u-law/a-law? Conversely, has anyone had any negative results from using G.729 that they saw were eliminated by switching to G.711?

I haven't had any guinea pigs to phone to really test these two codecs (the only two my VOIP provider seems to support) side-by-side and be sure for myself. I plan to when I can but I wanted to see what some of you guys results have been.

[tulare]

Yes, I tried it recently. I have BROADVOICE with Comcast internet service.My test lasted one day.I could not surf and talk on phone at the same time. G.711 seems to work better for me even without QOS setup.

[kitonne]

Problem is that voice quality is related to both bandwidth and link quality (% of dropped packets) in voip over public internet. If you use a LAN, with QOS mixed in, G711 sounds better then G729 (although not by a wide margin, imho). While you always have dropped packets if you try to push more data then the available pipe, you may have a significant % of dropped packets in pipes two to three times wider then your stream. I did quite a few tests with friends on DSL and cable, and number of dropped packets was about the same regardless of the codec (Thank you Sipura for providing a nice, easy, way to track number of dropped packets!)

If you go over the internet, the higher the bandwidth you use, the more likely it is to have some dropped packets somewhere between here and there (and the spec of your link to your ISP is just one in the long chain the packets need to go through). Both G711 and G729 work well over most broadband links in US and Canada. Once you try to reach places 30 hops away, both codecs are likely to have quality challenges due to dropped packets somewhere in between. iLBC codec (see Grandstream products) may be your only chance for reasonable voice quality over such links.

If the pipe is wide enough, and you have a couple of dropped packets, G711 will sound better then G729, as compressed codecs react worse to dropped packets (iLBC being the notable exception), when compared to G711. On the other hand, G711 is a bandwidth hog compared to G729, so the message is do your own testing

[CJohnston]

ctylor,

With my BroadVoice line, I actually had a lower noise-floor (that constant white noise that resides in the background) while running G.729a than with the high-quality G.711u. Because of this, I actually chose to run with the G.729a codec full-time before I stopped using BroadVoice in favor of VoicePulse.

With the new VoicePulse line, I haven't even dropped my codec from G.711u because the noise floor is much quieter on G.711u than with either codec on the BroadVoice line. Plus I've had no problems, so I see no reason to reduce my codec quality unless I'm having issues.

[ctylor]

Thanks guys for all your comments. I hope they are helpful to future readers of this forum when people consider the merits between PCM-A/PCM-U (i.e. G.711) and G.729a/b for their particular connections.