QOS Parameter questions

[cjk03b]

We have been looking at the Zoom Phone system QOS to determine why some clients are reporting poor sound quality occurring 1-2 times per week. To be more specific, callers are reporting that our user sounded distorted or echo-ey while we heard clearly from them. We ran a certification on the wired network ports, patch cables, and phone cables. We were able to look at specific events, and the QOS showed that they were 4.1-4.5 good quality calls. The only commonality I could see between them was that they all showed a 12kbps sending bitrate when known good calls showed a 50-75kbps sending bitrate.

Zooms website says that bandwidth needs are 60-100kbps for calls.

Could this actually be the cause of the poor sound quality? If the recommended bandwidth is 60-100 kbps, why is it rating a 12kbps call is good quality?

[Eliot]

hi cjk03b,

Recommended bandwidth bit rate for each simultaneous call of 60-100 kbps covers different types of codecs which include fixed and variable rate codecs.  Fixed rate codecs include G711 (64 kbps) and variable rate codecs include Opus.

Review  voice codec and isp on poor quality calls.  Opus codec adjusts its bit rate to network conditions.  12kbps would indicate Opus has adjusted its bit rate down to deal with less than perfect network conditions.  The network conditions include the call paths all the way from your phone to the other party’s phone via your LAN, your ISP, your client’s ISP, your client’s LAN and your client’s phone and also include the return path from your client to you.

Viewing the Zoom Phone quality of service dashboard

Frequency: The audio frequency sample rate being sent and received. Typically a sample rate in the range of 16 to 48kHz is acceptable. A higher frequency means better audio quality.

Codec: The audio codec being used by Zoom Phone. Usually, you'll see Opus, an audio codec that ensures high-quality audio.  The codec takes the analog voice signal and converts it to a digital form for transmission over your network and the Internet.

Accessing meeting and phone statistics (zoom.com)

Did my response answer your question? If so, please don't forget to mark the reply as an accepted solution.

thanks,  eliot

[tonystark1122]

Certainly! Could you please specify the QoS (Quality of Service) parameters you have questions about? This will help me provide you with the most relevant information.

[cjk03b]

I was working off the assumption that the bandwidth was pre-codec, not post, and that the ~12Kbps may be related to the poor sound quality. What I am trying to figure out is why we have unsuccessful calls where clients get no connection or where they get poor voice quality, but the QOS indicates it was a great quality call. Some times this happens on a cell phone on the wireless network, other times it happens on a Yealink desk phone (t46u or t57w). It happens maybe 1-2 times per week for a few users that have reported it. When they can provide specific time stamps and phone numbers with no connection or poor sound quality, the QOS tool indicates there was no issue.