Audio Problem: Audio Drop-outs or Stutters

Symptoms

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

Sample WAV file: ​http://www.pjsip.org/trac/attachment/wiki/audio-problem-dropouts/stutter.wav?format=raw

In the WAV file above, you can hear the stutters at 2.5 second, 3.8 second, 8.8 second.

Checklists

Checklists:

1. Check whether the symptom is observable when looping the microphone to the speaker locally.
2. Check for network impairments of incoming RTP packets
3. Check that CPU Utilization is not Too High

Windows Mobile Workaround

Some people have observed stutters on Windows Mobile devices, and it turns out that this was caused by frame duration setting that is set too low. The usual settings for frame duration is 10ms or 20ms, and it seems that Windows Mobile just can't handle this. Increasing the frame duration to 80ms seems to cure the problem.

Example:

This sets the frame duration to 20ms:

 int samples_per_frame = clock_rate * 20 / 1000;

While this would set the frame duration to 80ms:

 int samples_per_frame = clock_rate * 80 / 1000;