Motion compensation filtering in an image system
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 pixel value interpolation of a current frame in an image system, the method comprising:
applying a motion compensation filter for fractional motion vector displacement on integer pixel points of a reference frame to determine a value for a fractional point, the motion compensation filter including a positive lobe between two negative lobes,
wherein the reference frame is further distant than another referenceable frame in display order to the current frame;
receiving a signal identifying the another referenceable frame as expired; and
in response to the signal, discarding the another referenceable frame as a referenceable frame.
2. The method of claim 1 , wherein the reference frame is a predicted frame.
3. The method of claim 1 , wherein the reference frame is an intra frame.
4. The method of claim 1 , wherein the another referenceable frame is a nearest referenceable frame to the current frame.
5. A computer-implemented method for pixel value interpolation of a current frame in an image system, the method comprising:
accessing a reference frame, the reference frame being spaced apart from a current frame by at least one intervening referenceable frame in display order, wherein the reference frame comprises one or more picture regions, each of the picture regions comprising a set of integer pixel points;
applying a motion compensation filter for fractional motion vector displacement on the set of integer pixel points of a selected one of the picture regions of the reference frame to determine a set of values for fractional pixel points, the motion compensation filter including a positive lobe between two negative lobes;
determining pixel values for a picture region of the current frame based on the set of values for the fractional pixel points;
receiving a signal identifying the reference frame as expired; and
in response to the signal, discarding the reference frame as a referenceable frame.
6. The method of claim 5 , wherein the reference frame is a predicted frame.
7. The method of claim 5 , wherein the reference frame is an intra frame.
8. The method of claim 5 , wherein the reference frame is subsequent to the current frame in display order.