Retime video and audio using Compressor
To retime video using Compressor, you make changes to properties in both the General inspector and the Video inspector. (You can create some effects by modifying properties in only one of the inspectors.)
The Retiming section in the General inspector allows you to define a new speed setting for the clip. You can specify a percentage, such as 50% to create a slow-motion effect, or 200% to create a fast-motion effect. You can identify a precise number of frames and allow the software to calculate the percentage for you; or you can instruct Compressor to renumber the current frames into a different frame rate in order to convert a file from one frame rate to another without adding or deleting any frames.
In the Video Properties section of the Video inspector, you can set a specific frame rate for the transcoded file. By default, this property is set to Automatic, which applies the frame rate of the source file to the output file.
If the source media file contains audio, retiming modifies the audio speed as well, thereby keeping audio and video in sync. Compressor also automatically corrects the pitch so the audio doesn’t sound artificially high or low.
Important: If you modify retiming properties in a setting that uses the QuickTime Movie format and choose “Copy audio tracks from source” in the Audio inspector, the audio speed is not changed. Consequently, audio in the output file will not maintain sync with the video.
In the Quality section of the Video inspector you can set the retiming quality to specify the processing method used when you make changes to other settings that modify the speed or frame rate of a clip.