System and method for video processing
View Patent ↗A video program length is changed by processing an MPEG compressed video signal. Two temporally adjacent B-frames are selected, by looking for pairs with small differences. The selected B-frames are combined to create at least one intermediate frame; which is inserted in place of or between the selected frames. Presentation time stamps are altered to provide a uniform display rate.
1. A method of changing a video program length by processing, using a processor, a compressed video signal which represents the video program, the compressed video signal including frames in different prediction categories, one prediction category comprising frames (B-frames) which are not employed in the prediction coding of other frames, the method comprising the steps of:
selecting at least two temporally adjacent B-frames;
combining, using said processor, said selected B-frames to create at least one intermediate frame; and
inserting said intermediate frame or frames into the compressed video signal to change the program length of the video program.
2. A method according to claim 1 , wherein temporally adjacent B-frames are selected in dependence upon a measured difference between adjacent frames.
3. A method according to claim 1 , wherein the compressed video signal includes motion vectors for each B-frame and wherein temporally adjacent B-frames are selected in dependence upon the motion vectors of adjacent frames.
4. A method according to claim 1 , wherein the step of combining frames comprises taking an average of those frames.
5. A method according to claim 1 , further comprising adjusting the presentation time stamps of the signal to ensure that the output frames are played at the desired frame rate.
6. A method according to claim 1 , wherein candidate frames are replaced by a smaller number of intermediate frames to decrease video program length.
7. A method according to claim 1 , wherein an audio signal accompanying said video signal is time compressed or expanded to a corresponding degree.
8. A method according to claim 7 , further comprising the step of correcting for any loss of lip-synch.
9. Apparatus for changing a video program length by processing a compressed video signal which represents the video program, the compressed video signal including frames in different prediction categories, one prediction category comprising frames (B-frames) which are not employed in the prediction coding of other frames, the apparatus comprising:
a frame selector for selecting at least two temporally adjacent B-frames;
a frame combiner adapted to combine said selected B-frames to create at least one intermediate frame; and
means for replacing said selected B-frames with said intermediate frame or frames.