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 computer-implemented method that uses a processor for video image compression using direct mode prediction, the computer-implemented method including:
accessing a sequence of predicted and bi-directionally predicted frames each comprising pixel values arranged in picture areas, wherein at least one of the picture areas in at least one of the bi-directionally predicted frames is predicted from picture areas in one or more reference frames using direct mode prediction; and
determining a predicted motion vector with a frame-distance method,
wherein, given a predicted picture area in a first reference frame, a predicted frame of the predicted picture area, and a motion vector that corresponds to a co-locating picture area in a second reference frame, the predicted motion vector is linearly proportional to the motion vector and a distance between the predicted frame of the predicted picture area and at least one of the first or second reference frames.
2. The computer-implemented method of claim 1 , further comprising referencing a second predicted frame from the second reference frame by referencing the second predicted frame with the predicted frame of the predicted picture area.
3. The computer-implemented method of claim 1 , further comprising associating the predicted picture area with reference frames comprising at least one of the first reference frame or the second reference frame.
4. The computer-implemented method of claim 1 , wherein the frame-distance method comprises a function of a frame scale fraction.
5. The computer-implemented method of claim 4 ,
wherein the frame scale fraction comprises a numerator and a denominator,
wherein the numerator of the frame scale fraction is proportional to a first frame distance from the predicted frame of the predicted picture area to the first reference frame and the denominator of the frame scale fraction is proportional to a second frame distance between the first reference frame and another reference frame referenced by the first reference frame.
6. The computer-implemented method of claim 1 , further comprising providing both the first and second reference frames in a display order that is prior to a display order of the predicted frame of the predicted picture area.
7. The computer-implemented method of claim 1 , further comprising providing both the first and second reference frames in a display order that is subsequent to a display order of the predicted frame of the predicted picture area.