3.7.2. The Timeline Cache

The timeline cache system helps to ensure smooth playback of any timeline, regardless of the timeline’s complexity or the hardware being used. Very little effort is required; a one-time configuration allows you to choose your desired settings, after which the system functions automatically in the background.

The cache creates rendered images of each frame of your timeline, so rather than needing to try render each frame in real-time during playback, your system simply reads and displays the pre-rendered frame in the cache. This can dramatically improve playback on affordable systems with less robust hardware, or for very complex timelines which could cause any system to struggle.

• Timeline Cache Button: Click this button at the top right of the timeline to force a cache of the current timeline to begin rendering immediately.

Working with The Timeline Cache

The timeline cache is created automatically during periods when your processor is idle. You may want to do some initial configuration, however, if you don’t wish to use the default settings. The Cache consists of two main components:

• The Database: This file keeps track of which cache files belong where, so they can be quickly accessed.
• The Cache: This folder stores the pre-rendered images of each frame which has been cached.

Configuring the Timeline Cache

1. Open the Options (File > Options) and select the Cache tab.
   1. Select the location where the Database and the Cache will be stored.
      • If you wish to use the default location, you can skip this step.
      • If you prefer to store your proxies on a secondary drive, or a specific location on your system drive, choose your desired location.
   2. Define how long cache files will be retained
      • Keep Unused Files: Cache files for larger project can take up a significant amount of space. The system will automatically delete cache files if they have not been used for a period of time, specified here. This frees up that drive space for other use. Any project which remains unopened for longer than the amount of time shown here will need to be re-cached once it is opened again.
   3. Choose whether the cache is created automatically or manually.
      • The Create Timeline Cache in Background toggle is enabled by default, so the cache will be created automatically. If you want to retain full manual control over what is cached, and when, then disable this toggle.
      • Cache In Background After: Sets the amount of time the processor must be idle before the cache begins rendering when the Create Timeline Cache In Background option is enabled.

Manually Controlling the Cache

You can manually initiate caching of any timeline immediately, at any time. If you choose to disable auto caching in the background, this is the only way to generate a timeline cache.

• Timeline Cache Button: Click this button at the top right of the timeline to force a cache of the current timeline to begin rendering immediately.

Clearing the Cache

There are a number of ways to clear the cache.

• Options: The *Delete Timeline Cache” button found at File > Options > Cache will delete all timeline cache files present on your system, for all HitFilm projects.
• Timeline: Changing any aspect of a clip in such a way that it alters the clip’s appearance in the viewer, will clear any cached frames which include that clip. These changes can include, but are not limited to:
  • Transform controls
  • Clip visibility
  • Adding or editing effects
  • Adding or editing masks

Caching Multiple Versions

The timeline cache is always created using your current playback resolution and playback quality, as selected in the Viewer menu. Changing the playback options does not delete any existing cache files. Instead, it will initiate creation of new cache files, so that each combination of playback settings you select will have its own cache files. This allows you to switch between different configurations of quality and resolution without needing to re-render the cache every time. When a combination of quality and resolution is selected for which a cache has already been rendered, that cache will immediately be recalled and used to display the timeline.