High Variance and Spikes: Inbound Video Bitrate

Q. Why are there fluctuations and spikes for the inbound video bitrate?

1. Variance in bitrate can reflect the level of activity in the video stream.

It can be perfectly normal to see a small amount of bitrate variance in a stream based on action in the video. For example, if you do not have a lot of action in the stream such as a person talking, but suddenly switch to a significant amount of activity such as football players running, you may see a sudden increase in the incoming bitrate.

In the example below, the Wowza Video dashboard displays normal variance in inbound bitrate based on activity in a stream. 

Healthy Inbound Bitrate Based on Stream Activity:


If you see a high variance in the video bitrate, but a stable frame rate and audio bitrate, this could indicate the encoder and network are working fine, but either the action is changing drastically in the live stream, or you haven’t set constraints for an upper bitrate limit within the variable bitrate parameter.

For a stream with a variable bitrate setting, you would expect to see a large fluctuation in the bitrate. If you are using a constant bitrate, however, high variance could indicate a potential problem.

2. Unhealthy Spikes in Inbound Video Bitrate:

 If you see a high number of spikes in the video bitrate when there is low activity in the stream, your bitrate is potentially unstable and, as a result, you may see additional problems with frame rate and frame loss.

Unhealthy Stream and an Encoder that is Overloaded:


Possible causes:

  • Lack of bandwidth
  • Incorrect encoder settings
  • CPU load is too high
  • Encoder hardware issue
  • The video bitrate is set too high

Troubleshooting tips:

  1. Use a constant bitrate (CBR) for a more reliable stream
  2. Check your encoder settings for bitrate and frames per second (FPS)
  3. Check the CPU load
  4. Stop all other processes consuming bandwidth and memory
  5. Switch to a different network if possible



View Stream Health Metrics in Wowza Video

Using Health Metrics to Troubleshoot Live Stream Issues