Interpolation of video compression frames
Coding techniques for a video image compression system involve improving an image quality of a sequence of two or more bi-directionally predicted intermediate frames, where each of the frames includes multiple pixels. One method involves determining a brightness value of at least one pixel of each bi-directionally predicted intermediate frame in the sequence as an equal average of brightness values of pixels in non-bidirectionally predicted frames bracketing the sequence of bi-directionally predicted intermediate frames. The brightness values of the pixels in at least one of the non-bidirectionally predicted frames is converted from a non-linear representation.
1. A method for decompressing a video image with a processor, the method comprising:
receiving a sequence of predicted and bi-directionally predicted frames, each frame comprising respective pixel values arranged in picture areas, wherein a particular picture area in a particular bi-directionally predicted frame is predicted from picture areas in a first reference frame and a second reference frame using direct mode prediction;
determining, for the particular picture area in the particular bi-directionally predicted frame, a predicted motion vector with a frame-distance method, wherein, given a picture area in the first reference frame and a motion vector of a co-locating picture area in the second reference frame, the predicted motion vector is linearly proportional to the motion vector and a distance between the particular bi-directionally predicted frame and at least one of the first reference frame or the second reference frame;
determining using the predicted motion vector an area for motion compensation in the first reference frame or the second reference frame; and
applying a motion compensation filter for fractional motion vector displacement on integer pixel points in the area for motion compensation, wherein the motion compensation filter includes a positive lobe between two negative lobes.
2. The method of claim 1 , wherein both the first and the second reference frames are prior to the particular bi-directionally predicted frame in display order.
3. The method of claim 1 , wherein both the first and the second reference frames are subsequent to the particular bi-directionally predicted frame in display order.
4. The method of claim 1 , wherein the predicted motion vector is inversely proportional to a distance between the first reference frame and the second reference frame.