Tips on Importing Source Media Files

Here are some additional tips on importing source media files.

Highly Compressed Source Files

It is strongly recommended that you do not use highly compressed source files, such as MPEG files, as your source files, because they can cause undesirable artifacts in the encoded video.

QuickTime Reference Movies

If you submit a reference movie for distributed processing, the Apple Qmaster distributed processing system will automatically copy the appropriate media files to the processing cluster. For the best performance, you can avoid this file transfer step by making sure that the media files specified in the reference movie are available to each node of the Apple Qmaster cluster. For more information, see How the Apple Qmaster System Distributes Batches.

Importing MPEG-2 Files

When you import an MPEG-2 file, Compressor must parse the file before you can play it in the Preview window. Parsing the file involves determining its frame structure and other necessary information about the file. Since the frame structure can change throughout the file, Compressor must scan through the entire file, which can take several minutes for longer files.

This does not happen with MPEG-2 elementary files encoded using Compressor that had the “Add DVD Studio Pro metadata” checkbox selected. See Extras Tab for more information.

About Dolby Digital Professional Source Media Files

You can use Dolby Digital Professional AC-3 audio files as source media files for your jobs. There are two common reasons to want to do this.

  • To test a file you just encoded: Since you cannot preview the Dolby Digital Professional output settings, importing an encoded file into a job allows you to play it and verify the settings.
  • To convert a Dolby Digital audio file to another format: Since not all media players include Dolby Digital decoders, you may find that you need to transcode the file into another format.

Compressor includes a Dolby Digital decoder that it uses whenever you play or transcode Dolby Digital audio files. This makes it possible to verify the Dolby Digital Professional output settings of a previously encoded file on your system without requiring you to have an external Dolby Digital decoder. To hear surround sound you must have an external surround sound device connected to your computer’s USB or FireWire output. The audio is mixed down to two channels if you play the audio using your system’s stereo speakers.

Important: Since the audio output is already decoded and not in the Dolby Digital format, the optical output cannot be used when playing Dolby Digital files from Compressor.

Tip: Add an .ac3 extension to the filename if Compressor does not allow you to add it to a job.

Automatic Values and Nonstandard QuickTime Files

Compressor uses a variety of tactics to determine the proper values for any settings that are set to Automatic. In most cases, QuickTime files contain metadata that specify the various attributes of the file, such as frame rate and frame size. In some cases, this metadata is not present, forcing Compressor to try to determine this information, or it is incorrect, causing Compressor to generate incorrect values for the Automatic settings.

Additionally, some QuickTime files use nonstandard settings that require Compressor to choose an automatic value that may not be suitable.

For these reasons, it is a good idea to verify the values in the Inspectors for those settings that are set to automatic. See About the Automatic Settings for more information.