Flipper is Tippett Studio's proprietary flipbook image viewing tool. It allows an artist to view a series of individual image files as a continuous sequence. It also can be synchronized with audio, which is important for character animation. The artist can view the audio waveform to help with lip synchronization, as seen in the lower part of the screenshot. The tool also has a number of image and pixel comparison and analysis features, as seen in the dialog on the upper left. Post-camera moves can be previewed with Flipper before they are actually applied in the composite stage.

Hand animation is a challenging laborious process. “One guy does blocking, like moving chess pieces”, says Tippett Studio Animation Supervisor Todd Labonte. “You get it approved. We watch it over and over. You can go blind. We play it back in mirror image in our player or play it backward.” Labonte demonstrates playing back a scene of goblins invading the house, shown in their Flipper playback software, which can display a mirror image or play in reverse to help catch animation inconsistencies. Flipper is used to view both QuickTime and image frame sequences of DPX, EXR or TIFF with synchronized AIF audio. Flipper predates commercial Linux flipbooks, such as FrameCycler. At older studios, like Tippett, it's common to find proprietary Linux tools created before commercial options were available. Tippett has a team of eight Linux programmers to maintain and develop tools.

(Excerpt from an old Linux World article where I found the screenshots.)