Q: In the stream health monitor I see my GOP fluctuates. How do I fix it?
A #1: Enable the "noscenecut" option in your encoder settings.
Some encoders allow you to "force" the GOP to a specific interval. We recommend 1 or 2 second keyframe intervals. If you utilize an encoder with the x.264 codec you may have an option to use "noscenecut" or "scenecut=0". This tells the encoder that no matter what content it is encoding, it will ignore injected keyframes when switching between sources and/or what may be within a recorded vod asset being restreamed.
A simple example is using OBS Studio and playing a video file as an opener and then switching to a live source. Typically, whenever there is a switch between sources, additional keyframes are introduced. This is why you would see peaks and valleys in the stream health monitor. The "noscenecut" setting places total GOP control with the encoder.
Example screenshot from OBS Studio on macOS with the "scenecut=0" option enabled:
A #2: You may have experienced network issues between your encoder and the transcoder.
There are times when you will notice the GOP is showing "peaks and valleys" in the stream health monitor. If the option above doesn't smooth that out for you, there may be a network issue in the "first mile" between your encoder and the transcoder. Typically, if there is a GOP issue present in a volatile network scenario, you would also see dropped frames as well. Instead of a flat pink line for the FPS we are receiving, you would see occasional "peaks and valleys" for the frame rate as well.
If this is related to the network path taken to the transcoder, there is really only one option to combat this: stop the transcoder and choose a different location. If your closest region is not working, choose the next closest region, and presumably, a different path to that region could solve the issue.
You can change the location of a transcoder by navigating to Advanced > Transcoders > [transcoder name] > Transcoder Setup tab > Edit > Broadcast Location > [choose new location] > Save.