Film Cadence Inspection Tool
Publication Date: 2014-Aug-20
The IP.com Prior Art Database
Film cadence inspection tool used to verify proper film cadence sequence as applied to video. If the cadence is broken, it can show the operator what is happening and provide a way to capture the details. This tool operates on the HBO mezzanine JPEG2000 stream, but can be applied to all interlaced 59.94 video.
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Film Cadence Inspection Tool
Field of Disclosure
The disclosure is in the field of video production and editing. This deals with video image sequences.
Problem to be solved
Since, in the U.S., film is typically shot at 24 frames per second (fps) while television video is broadcast at
29.97 fps, a frame conversion process is needed to avoid various visual artifacts that would otherwise mar film shown on television. Specifically, National Television System Committee (NTSC) Standard Definition (SD) and High Definition (HD) television which uses film as a source must be converted from film image display rate of 24 fps to an interlaced frame rate of 29.97 (3000/1001) frames per second. This conversion is called telecine. The telecine operation maps the images of film to video by generating additional video frames. One method to do this is known as 3:2 pulldown, also called 2:3 pulldown. One skilled in the art of this cadence understands the film to video relationship.
In interlaced video, each video frame comprises a pair of fields referred to as top and bottom or odd and even. Figure 1 shows how four film frames are converted to ten interlaced video fields, which will make up five video frames, thereby converting 24 film frames into 30 video frames. If the video is not edited, then converting back to film frames is relatively straightforward. However, if the video is edited, then the cadence can be broken.
De‐telecine - also called reverse‐telecine or inverse‐telecine - is shown in figure 3 and is the process of returning the video images back to their native 24 fps sequence. Figure 3 shows pairs of top and bottom fields combined to form the original frames and ignoring duplicate fields. This process is used when converting to a different frame rate like PAL, which is 25 fps, or transmission via MPEG to save bandwidth. The process described below may be used to validate the cadence and/or locate breaks in the frame sequence.
Summary of Invention
The present invention provides for an enhanced reverse telecine process. Automatically performing PSNR comparisons on pairs of video fields indicates whether the pair originates from the same film frame or different film frames. Generating difference images for pairs of video fields provides a visual indication of difference or similarity. Using one or both of the above‐described processes, a correct 3:2 sequence may be automatically and/or manually determined in the video sequence so that a clean reverse‐telecine into a corresp...