Okay there is some thought put into your choice of keyframe interval. And there is a conflict. You allow the aformat filter to negotiate for 5.1, 7.1, or ster

Okay there is some thought put into your choice of keyframe interval. And there is a conflict. You allow the aformat filter to negotiate for 5.1, 7.1, or stereo but then insist there must be 2 audio channels. I copy the audio when it is suitable just to save another lossy encode.