Rendered video pulses to lower quality and back to high quality In my output video there a pulse that occurs after the number of frames specified in the "GOP Size" setting. With the setting of 18 that I have in the image shown below, the pulse occurs every 18 frames. During this "pulse", the video seems to move to a lower picture quality and then quickly returns back to a high quality.

Here are my output settings:


If I set "GOP Size" to zero, the picture quality of the video degrades substantially. The maximum value for "GOP Size" seems to be 100, so the pulses occur a little over 3 seconds apart.

Is there anything I can do to alleviate this?

Any idea what I might be doing wrong?
The problem may be caused by some sort of glitch in the encoder included in Blender. The poor quality can be avoided by using lossless output. In v2.71 this is done by choosing H.264 format under Encoding, and ticking the Lossless Output box.



Here is a detailed video explaining lossless rendering in Blender.