Good morning!
A couple of weeks ago, I was troubleshooting a problem with poor voice quality when calling from Cisco Jabber software clients. The customer’s VoIP network covered several offices in different cities, CUCM 8.6 and СUP 8.6 were used. In general, there were about 1,500 users in their enterprise telephone network, and more than a thousand of them did not have Cisco hardware phones and called each other using Cisco Jabber.
The problem was that when calling from Cisco Jabber, users complained about poor voice quality, namely, interruption of speech, gaps, etc, while words and phrases were sometimes completely unintelligible. Moreover, the problem was present even when making calls within the LAN! Usually, this phenomenon is associated with network problems – a large percentage of voice packet losses. And the reason for the loss of voice packets could be a high jitter value, incorrectly configured queues on routers, insufficient bandwidth, enabled VAD, and the wrong choice of codec.
To estimate the percentage of lost packets when calling from Cisco Jabber, a number of test calls were made to a Cisco hardware phone 7941 and call statistics were taken through the phone’s web interface (which was previously enabled in the settings of the phone itself). The result was the following (I will give the results for calls over a LAN network without using WiFi and for a call via WiFi):
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Calling from Cisco Jabber over a LAN segment without WiFi
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| Calling with Cisco Jabber over WiFi |
As you can see from the given call statistics, there are no IP packet losses in the established voice session! The jitter was also within the normal range (< 30 ms). However, there was a speech quality problem that needed to be fixed. In order to be completely sure that the network is not the source of the problem (although this was already evident from the call statistics), we requested the configuration of network devices from the support team and made sure that the network settings were made correctly.
After receiving such results, it became quite obvious that the problem comes from the source of voice packets – a computer with Cisco Jabber installed on it. The customer used only 2 types of PC – HP and Lenovo. After conducting a series of test calls with both HP and Lenovo, it was found that problem calls are observed from Lenovo with a Connexant sound card. Moreover, it was found that the problem was observed when using a regular audio headset connected to the audio input of the PC. If the callers used a USB headset, the voice quality was significantly better. So, the PC Lenovo sound card was the source of the problem.
To solve the problem, it was decided to update the sound card driver for this PC model. The required driver was downloaded from the Lenovo official website. After updating the driver, the speech quality issue was fixed and user complaints stopped.
This is how, step by step, the cause of the described speech quality problem was clarified and eliminated. The customer is satisfied – Happy End 🙂
Good weekend!
Спасибо большое Дмитрий, за последовательно описанный траблшутинг! Никогда бы не подумал, что дело в драйвере сетевой карты. Зная сисадминов в нашей компании, они бы точно, не разбираясь, стали грешить на сеть (это моя зона ответственности).
Да, траблшуттинг удался. А вообще вот Connexant помню тож попортил нервов. Как-до довелось устранять проблему исчезновения звука на ноуте у клиента, так вот у него карта стала каким-то образом модемом (так драйвер принялся) и не хотела выполнять функцию, вообщем пришлось поставить драйвер принудительно и проблема решилась сама собой. стандартные дрова 7-й винды не прокатили.