[YMCS/YDMP Free Trial Program]Yealink would like to offer Free Trial Program of Yealink device management service for our current eligible customers. You can see the details below.
https://www.yealink.com/ydmp-freetrial-2020


Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
T41S: severe audio interruptions
Author Message
Kevin_Yealink Offline
Administrator
*******

Posts: 204
Joined: Jul 2016
Reputation: 2
Post: #4
RE: T41S: severe audio interruptions
(08-18-2017 05:49 PM)Anatoli Wrote:  Hi Kevin,

Thanks for following up the issue.

Answering your questions:

1. The audio issues happen in any type of communications: A>BPX, A>B, A<B, Opus/G722 (A/B/AB), MOH/speech/music. We use music to perceive better the interruptions as it's a continuous reproduction and playing MOH directly from the BPX excludes any quality degradations caused by the other endpoint, but human speech with another phone has the same problems.

After some extensive tests simulating different environment conditions (and rebooting the device multiple times) we were not able to consistently reproduce the more severe interruptions. It looks like there were 2 issues: some strange interruptions that could last for 3-4 seconds or more and repeat very frequently (and sporadically, like in the first post where a second call had no such issues) and small interruptions due to environment issues (network delays, packets reordering, etc.).

We came to a conclusion that the small interruptions issue is due to deviations of the packets order/timing from the absolute perfect condition. It looks like our Yealink phone is extremely sensitive to any deviation in order or latency, it doesn't compensate for this imperfections with adaptive jitter buffer (was configured with "adaptive,20,200,20"). At the same time, Linphone was able to "eat" most of the environment issues without audible defects or with light sound distortions.

At the same time, for unknown reason, Yealink phone was always behind Linphone in audio reproduction, sometimes with a delay of up to 300-500ms, most of the time around 80-100ms (subjective judgment). One could guess that this could be an extremely large jitter buffer, but the small interruptions were happening with this delay too.

When enabled Settings > Voice monitoring > Display Report options on phone, there were strange statistics. JitterBufferMax, Packets lost and RoundTripDelay were always at 0, but Jitter had strange numbers: it could stay at 0 when there really was jitter, after one reboot it stayed constantly at 950-960 without dropping to normal values though there was no such jitter. At other times it was varying from 0 to 400, but not consistently, i.e. when there was jitter, the value sometimes was staying without change, at other times it was following the real jitter pattern. At the same time Linphone was changing its jitter buffer from 0 to 90ms, staying most of the time at around 40ms (via WiFi).

We got an impression that there was no jitter buffer enabled at all or it was discarding buffered data too quickly as the phone was not able to compensate for most deviations. I'm not sure if this is a standard behavior or we got a defective unit, or there are some options we're not aware of that deal with this sort of issues.


2. We don't have another Yealink or any other (non-Cisco) hardphone at hand, but were using multiple smartphones (iOS/Android) and PCs (Win/Mac/Linux) with Linphone, WiFi and cable connections. Everything works well in any combination, except the Yealink. Even tried disconnecting Yealink's cable and connecting it to a PC with Linphone.

3. Syslog and PCAP files attached: yealink.pcap is a pcap generated by the phone for about a minute of a call to PBX with MOH, fs.pcap is a pcap generated at the Linux machine running FreeSWITCH BPX almost at the same time as yealink.pcap (was started some seconds before and was turned off some seconds after). We generated varying CPU load at the PBX machine during this recording to cause some jitter and got a lot of small interruptions on Yealink. During this recording the same channel was reproducing on Linphone without interruptions (there were 2-3 very light sound distortions for about half a second).

4. Depending on the demand from our clients, we expect that we could purchase some 20-30 phones this year and more in the future. We're currently using Cisco 7900 + chan_sccp_b + Asterisk with G722 and would like to setup new deployments with Yealink T4S + FreeSWITCH using Opus (and, according to our clients' decision, possibly migrate existing deployments).

We really like the new T4S line for the features, ease of configuration (compared to the Cisco phones) and its look&feel, but we can't put it in production with this performance.

Please let me know if you need additional details.

Regards,
Anatoli

Hi Anatoli

Sorry for late reply. I miss this forum as i don't receive reply nitification. Really sorry about this.

For this issue, i already submit it to R&D, and i will give you update.
I will also send you email by my private email. Maybe we can follow this case via email system.

Best Regards,
Kevin
09-04-2017 06:24 AM
Find all posts by this user    like0    dislike0 Quote this message in a reply
Post Reply 


Messages In This Thread
T41S: severe audio interruptions - Anatoli - 08-14-2017, 03:43 PM
RE: T41S: severe audio interruptions - Kevin_Yealink - 09-04-2017 06:24 AM

Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Problems with bluetooth audio ccwtech 16 3,349 09-16-2020 07:20 PM
Last Post: complex1
  Yealink T41s Multiple sip Accounts scorpio313 0 605 07-30-2020 08:13 PM
Last Post: scorpio313
  Permanent forward T41S microdata 1 979 05-28-2020 03:56 PM
Last Post: jolouis
  T41S units asking for last 5 digits of serial number then reseting to factory richard.vince 1 1,604 04-08-2020 08:16 AM
Last Post: complex1
  T41S pickup call with Swyxit qaztan 0 757 02-17-2020 04:39 PM
Last Post: qaztan
  Emergency Call over T41S Tino1977 1 1,084 12-19-2019 01:03 PM
Last Post: complex1
  T41S recovery from TFTP fails jwhopkins 3 3,163 07-25-2019 01:19 AM
Last Post: Baron_Yealink
  Intermittent No Audio Issues Timothy 0 979 04-29-2019 07:45 AM
Last Post: Timothy
  Muffled Audio on T46S btvoice 0 1,122 04-26-2019 03:17 PM
Last Post: btvoice
  Yealink T46S/T40G muffled/feint audio Stacy63 1 2,653 12-12-2018 02:50 PM
Last Post: complex1

Forum Jump:


User(s) browsing this thread: 1 Guest(s)

Contact Us   Yealink   Return to Top   Return to Content   Lite (Archive) Mode   RSS Syndication