Set a poster frame in Compressor
The poster frame is a still image that represents a video or audio media file or a podcast chapter in applications such as Music and in the Finder.
Note: When viewing the output file in Apple TV Home Videos, if no poster frame is set, Apple TV Home Videos automatically uses the frame 10 seconds from the movie’s first frame as the poster frame.
Set the poster frame for a job
In the Compressor batch area, select the job that contains the source file that you want to set a poster frame in.
Tip: To select the job, rather than an output row under the job, click the source filename at the top of the job area.
In the preview area, position the timeline playhead
at the frame you want to be the poster frame.In the preview area, click the Marker pop-up menu
, then choose Set Poster Frame.
A poster frame marker 
appears in the timeline.
Go to the poster frame
In the Compressor preview area, click the Marker pop-up menu
, then choose Go to Poster Frame.
Remove the poster frame
In the preview area, click the Marker pop-up menu
, then choose Clear Poster Frame.