When you upgrade to QuickTime Pro, "Play All Frames" is one of the features that becomes active in QuickTime Player—to enable the option, choose Play All Frames from the View menu (or Movie menu in QuickTime 6) to place a check mark by it.
This feature may play movies back differently than if you just click the Play button in QuickTime Player.
When you click the Play button, QuickTime Player automatically adjusts the video performance to provide the best possible presentation on your particular computer. If a movie is supposed to be exactly one minute long, QuickTime Player will make sure that the movie plays for exactly 60 seconds.
This can be a tough job if the movie was made on a fast computer and then played back on a slower computer that might not handle video as well. On a slower computer, QuickTime Player will skip frames to keep up with the time constraint if the movie contains more frames per second than it can handle.
The "Play All Frames" feature takes a different approach to performance. Instead of trying to keep up with the time, QuickTime Player will play every frame of the movie, without regard to how long it takes, when the feature is enabled.
Note: When you choose to play all frames in a movie, the audio track will not play.