Caches are a key part of any computer system and effectively are temporary stores designed to retrieve data quickly. For example, browsers use them so you don’t have to keep downloading the same images again and again and caching appears in two places in Pro Tools disk caching and Wave Caches for the waveforms in the clips.
Disk Cache (Pro Tools HD Only)
In the Playback Engine the Cache Size setting how much Memory (RAM) the Avid Audio Engine (AAE) allocates to pre-buffer audio for playback and recording. In most cases, the default setting of Normal is the best Cache Size for most sessions.
With Disk Cache in operation, Pro Tools HD loads some of the audio files used in Pro Tools sessions into RAM for cached playback so speeding up playback as Pro Tools doesn’t have to pull the files off the hard drive. Pro Tools will load the audio files nearest to the cursor or playhead location. This is especially useful when working with shared media storage whether it is from an Avid Unity ISIS shared storage system or a small network attached storage drive on your home network. The primary advantage of the Disk Cache feature is that it will take the load off your storage media, because Pro Tools has pre-loaded the media into RAM.
To determine the maximum amount of RAM available for the Disk Cache, Pro Tools checks how much RAM you have in your computer and subtracts 4 GB so in the screen shot above the computer has 24GB of RAM.
You can use the Disk Cache and Memory meters in the System Usage window to determine whether to assign more or less RAM to the Disk Cache for the current session. In this example the Disk Cache is full up but it is not clear if the whole session has been loaded. If you hover over it with the display tips option on it will tell you if you need to allocate more RAM to the disk cache to get the full session into RAM.
The other place Pro Tools uses caches is for the storage of the waveform data which it stores in the WaveCache.wfm file.
By storing waveform data in the WaveCache file, sessions open more quickly. The session WaveCache file can be included whenever a session is transferred to another Pro Tools system (7.x and higher).
Deleting or trashing a WaveCache file will not mess up your session or your system. However, be aware that when you next open the session it will take longer because Pro Tools has to recalculate waveform data for any associated audio files and create a new WaveCache file.
But before you delete this to deal with a waveform display issue it is always worth using the Recalulate Waveform option in the Clip List by right clicking on the problem clip in the clip list and selecting Recalculate Waveform Overviews. If that doesn’t fix it then it is worth considering deleting the WaveCache file.
You may not find a WaveCache file in the Session folder but Pro Tools maintains another WaveCache file inside the Databases folder. This global WaveCache file stores waveforms that cannot be written back to the sound file, such as read-only files, files on network and other read only volumes, and interleaved files.
On Mac, the WaveCache file is stored in /Users/Shared/Pro Tools.
On Windows, the WaveCache file is stored in <Systemdrive>/Users/Public/Pro Tools.
Recently we went through a renaming process in Pro Tools to align the names wth Media Composer and at that point what had been called regions ever since Pro Tools started became clips.
What is a clip?
A clip is a segment of audio, MIDI, or video data. A clip could be a drum loop, a guitar riff, a verse of a song, a sound effect, some dialog, or an entire sound file. Because a clip can be a segment of a file or the whole file it can be confusing to know which is which. But there are several tips to help yout to identify them.
In the clip list, what we used to call the region list, some items are in bold type and some are in light type. The bold type ones are the whole files, the original media. The light type items are edits from those original files. You can see in the screenshots above that on the right, there is an original file “Anna 2 rt1” in bold type, and then below there are a number of items in light type which are edited clips based on the original file. Because Pro Tools is non destructive in the way it edits, you won’t find a file called “Anna rt1-04” in the Audio Files folder. As you see on the left the only files in the Audio Files folder for the session are the original files which are displayed in bold type in the clip list.
Because you can rename clips it isn’t aways clear what the original file name is. A recent feature has added clip info to the Name window which enables you to see what the original file was called.
Double click with the Grabber tool on a clip on the timeline and the Name window will open. If it looks like the one on the left, then click on the little triangle to the left of Clip Info and it will extend and display the info on that clip including the parent file’s name.