Audio Problem: Audio Drop-outs or Stutters

Symptoms

The audio is sounding like it's skipping some frames.

Sample WAV File

See the attachment on the bottom of this page. You can hear the stutters at 2.5 second, 3.8 second, 8.8 second.

(audio file courtesy of Chen Huan <chenhuan at sict.ac.cn> who managed to convince his girlfriend to record the audio for testing :) ).

Checklists

Here are the checklists related to stutters problem:

1. Check whether the symptom is observable when looping the microphone to the speaker locally.
2. Check that there is no dangling call in the PBX. A dangling call is call that is left active in the PBX because previous (pjsua) application has crashed.
3. Check for network impairments of incoming RTP packets
4. Check that CPU Utilization is not Too High
5. Try to enlarge PJMEDIA_SOUND_BUFFER_COUNT value by setting it in your pj/config_site.h. The default value is 6, and you can increase it to, say, 16. But be aware that enlarging this buffer will increase the audio latency, so you should find a minimum value where the sound quality doesn't break.
6. Check for audio underflows/overflows