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Yealink T48G adding 175ms on inbound audio

Discussion in '3CX Phone System - General' started by tyfrantz@gmail.com, Sep 21, 2015.

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  1. tyfrantz@gmail.com

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    I am testing several phones for an eventual 3cx deployment. The three phones I'm testing right now include: Cisco SPA 303, Yealink T20P, and a Yealink T48g (firmware 35.73.0.50).

    I love the T48G. It's affordable, it's fast, I love the dss keys, the flexibility, the interface, I love it all. However, upon extensive testing I have definitively identified that it is adding on the order of 175ms delay on outbound audio.

    I have two versions of 3cx running: one is hosted in Seattle through 3cxhost.com and the other is a local install on my LAN on one of my servers. I have the phones registered to both servers. In order to test latency I record finger snaps using Audacity and then I can quickly measure the distance between the sound waves and be very precise in my figures. Because latency is my biggest concern with this deployment, I have done extensive testing. My tests include extension to extension calling using the hosted server and the server on my LAN. While connected from extension to extension, I would mute one phone and would snap in the other recording both my finger snap and the sound on the other extension using an external microphone. My results were not impacted based on who called who first (ie ext 1 -> ext 2 vs ext 2 -> 1 didn't matter, which would have shocked me if it did). In the results below, I have obviously averaged because they weren't all EXACTLY the PRECISE same number of milliseconds, however if they were within 20 ms then I made them the same. Here are the results:

    Hosted Server
    SPA -> T20: 165ms
    T20 -> SPA: 165ms
    T48g -> T20: 165ms
    T48g -> SPA: 165ms
    T20 -> T48G: 340ms
    SPA -> T48g: 340ms

    LAN Server
    SPA -> T20: 45ms
    T20 -> SPA: 45ms
    T48g -> T20: 45ms
    T48g -> SPA: 45ms
    T20 -> T48G: 220ms
    SPA -> T48g: 220ms

    This is using the G711 on the t48. I tried some of the other codecs and didn't have any results that differed substantially from the above. At least, I think I tried others. I moved some of them up on the list in the phone settings, and then eventually removed all codecs but the one I wanted to try, and so I assume that forces it to use the remaining codec.

    Conclusion/Problem/Question: Why is the T48g adding 175ms to inbound audio?????? I really like this phone but I'm trying to shave down latency and working my butt off to do that and the T48 is kicking me in the teeth!

    Thanks,
    Tyson
     
  2. tyfrantz@gmail.com

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    Yes, it is a problem that it adds around 175ms of latency, absolutely a problem. The issue is with SIP trunking which adds its own 150-200ms of latency, compounded with phone-to-hosted-server latency of another 165ms making the total of about 350ms which isn't too bad and doesn't create much in terms of overspeak, but when you cross the 450ms or 500ms threshold you begin seeing overspeak between the two parties, depending on the rate of speech and things. So the T48 adding 175ms is taking me from about 350ms to 525ms. Some won't notice it, others do, and I personally definitely notice it when I'm having a conversation with a lot of Q&A or back and forth, you speak over eachother. If you use a PRI or PSTN or some other on-premise handoff, your trunks are probably adding 40ms at the most, and you won't even notice the extra 175ms. But I have to serve multiple offsite locations with DIDs in other LATAs and none of the Tier1 on-premise handoff solutions can port or handle all of my LATAs, whereas many SIP trunk providers can. NOTE however that my experience is the same as yours; the quality is excellent! I am otherwise completely happy and ready to buy fifty of the T48s for my staff if I can resolve this one-way audio latency issue. In fact, it's an amazing phone. I'd love to see a few changes to the gui, but they outdid themselves on this one, and to be able to make it so affordable too.

    But perhaps the new firmware update will fix it; I'll give that a try. Somehow I was under the impression that I had the latest firmware; obviously I didn't look very hard. Thanks for pointing that out.
     
  3. tyfrantz@gmail.com

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    Upgraded firmware to 35.80.0.70 and still the same issue; the t48 adds about 175ms in delay to received audio....
     
  4. lneblett

    lneblett Well-Known Member

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    have you checked the jitter buffer settings?
     
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