Why do some DH_Subtitle clips require rendering?

Symptom

Earlier DH_Subtitle clips in the sequence play in real time but later clips require rendering.

Solution

In most cases, DH_Subtitle clips will play in real time over a background layer because Final Cut Pro keeps them in memory. However if you have many DH_Subtitle clips in a sequence then later clips may need to be rendered. This occurs when memory required by still frames (including generators like DH_Subtitle) exceeds the memory allocated in the Still Cache setting.

By default, the Still Cache is set to use 10% of the system memory but it is possible to enable real time playback of more DH_Subtitle clips by changing the setting:

1. Choose Final Cut Pro > System Settings and select the Memory & Cache tab.
2. Change the Still Cache percentage to a higher value.
3. Click OK to implement the change.