Apple Compressor 3 - Manual (Page 320)

Playing Dolby Digital Professional (AC-3) Files in the Preview Window
You can use the Preview window to play back Dolby Digital Professional (AC-3) files.
Compressor includes a Dolby Digital decoder so that when you add an AC-3 source
media file to a batch and play it, you are able to hear it using your computer’s current
speakers. This includes everything from the built-in stereo speakers, which play a
mixed-down version of the AC-3 file if it contains more than two channels, to a set of
external surround speakers connected to a USB or FireWire output.
Important: Since Compressor is decoding the Dolby Digital audio file, you cannot use
your computer’s optical output to preview Dolby Digital audio.
This feature is important if you are using the Dolby Digital Professional encoder since
you cannot preview the encoder’s settings in real time in the Preview window. Instead,
you can add the encoded AC-3 files to a batch and play them to verify that the encoder’s
settings produced good results. See
Transcoding a Portion of the Clip with the Preview
Window for information on creating a short test clip for this purpose.
Transcoding a Portion of the Clip with the Preview Window
Although Geometry (cropping and scaling) and Filters adjustments are displayed instantly
in the Preview window, Encoding pane and Frame Controls pane settings are not. To
preview Encoder pane and Frame Controls pane settings, do a test transcode of a small
section of your source media file.
You can use the Preview window to set In and Out points to transcode only a portion of
your media file rather than transcoding the whole thing.
To designate a portion of your media file for transcoding
1 Open the Preview window.
2 Choose a clip from the Batch Item pop-up menu or click the Batch Item selection buttons
until the clip appears in the pop-up menu.
3 Do one of the following:
• Drag the In point to the appropriate location.
320 Chapter 26 Using the Preview Window