Importing and Conformed Audio Files

When you create a new project, one of the Project Settings you assign is the Sample Rate for audioeither 16-bit 48kHz or 16-bit 32kHz for standard DV. When you later import an audio file or an audio and video file, Premiere Pro looks at the audio's bit depth and sample rate and determines whether or not it needs to conform it to match your project's settings. The rules for conforming are as follows:

• Any audio that is compressed (MP3, AIFF, WAV, and so on) is always conformed regardless of the kHz setting.

• Uncompressed audio (WAV, AVI or AIFF) that has a ratio of 1:1, 1:2, or 2:3 to the project's sample rate is not conformed. This means that uncompressed 48kHz audio in a 48kHz project will not be conformed (1:1). Also, uncompressed 32kHz audio in a 48kHz project will not be conformed (2:3).

Tip

For the sake of drive performance and application responsiveness, keep your conformed audio files on a separate drive from your original source files. If your drive is slow, having to access both the source media and the conformed files from the same drive can create a bottleneck. You can specify your storage locations from Edit > Preferences > Scratch Disks.

When the program creates conformed audio files, it increases the file to 32-bit resolution while increasing or decreasing the sample rate to match the project's kHz setting. Premiere then uses these conformed audio files along with the peak files to display the waveform information in the timeline and Source Monitor, to apply effects, and to play back the audio for the clip. Once you engage playback in Premiere Pro, if your DV camera is connected, the audio will always transmit at the proper bit and sample rate.

Conformed files are temporal, meaning that deleting them does not corrupt or destroy your project. If Premiere does not detect conformed files when opening the project, it creates new ones. When you import a file with audio, watch the conforming progress bar update in the bottom-right corner of the application's window. Once the bar completes, the conformed file is created and ready to use whenever you play back the audio clip. Fortunately, the management of conformed files is greatly improved in Premiere Pro 2.0 and that is all thanks to the Media Cache Database.