Bug 358997

I shoot in AVCHD. When I jog thru my clips forward, I usually can move frame-by-frame and my monitor is updated for every frame. When I move backward, I usually see no updates in the monitor until I encounter a key frame. I used to create proxies to mitigate this problem. The profile I use to encode my proxies is DNxHD 720p@60M - this is what my laptop can handle.

When my proxies are created, I expect that the playhead movements are updated in the monitor as they go. I see the same keyframed update of the monitor when I go backward instead. Besides that, the quality of the monitor stays at 1080p as originally filmed instead of going down to 720p. 

When I copy my proxy file and add it to the project bin as a usual clip, I can observe the expected smoothness of backward motion.   

Reproducible: Always

Steps to Reproduce:
1. create a DNxHD proxy of a 1080p @ 50 frames/sec
2. go back in either clip or project monitor
3. observe no frame update in backward jog.