I'm rendering some longer movies that have long sequences of duplicate frames, eg:

Molecule side view (5 seconds)
Rotate/Zoom (3 seconds)
Another view (5 seconds)

I've noticed that when using the mpng command, these duplicate frames are rendered, one after another...

Is there a setting I'm missing? cache_frames doesn't seem to prevent the behavior, and is unusable for longer movies. If not, may I humbly suggest this as a feature request? It could reduce rendering times significantly. I've debated scripting the duplication of a single frame post rendering, but I'm not sure it's worth the extra work.