Interpolation of video compression frames

Abstract

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 . (canceled) 
     
     
         2 . A non-transitory computer-readable medium storing encoded image data configured to be processed by one or more processing devices, the encoded image data comprising:
 picture frames comprising picture regions with pixel values in a compressed format, wherein at least one region within a predicted frame is determined using pixel values from at least a first referenceable frame and a second referenceable frame, the first referenceable frame being prior to the second referenceable frame in decoding order and subsequent to the second referenceable frame in display order, wherein the predicted frame is prior to both the first and the second referenceable frames in display order; and   an expiration signal that identifies the first referenceable frame as expired, and in response to the expiration signal, the first referenceable frame is discarded as a candidate referenceable frame in decoding the video bitstream.   
     
     
         3 . The apparatus of  claim 2 , wherein the bitstream further comprises weighting parameters identifying interpolation weights to interpolate pixel values of the at least one region within the predicted frame from pixel values of the first and second referenceable frames. 
     
     
         4 . The apparatus of  claim 3 , wherein the interpolation weights are unequal. 
     
     
         5 . The apparatus of  claim 3 , wherein the interpolation weights are determined based on a frame distance of each of the referenceable frames to the predicted frame. 
     
     
         6 . The apparatus of  claim 2 , wherein the bitstream further comprises a signal identifying how to interpolate pixel values of the at least one region within the predicted frame from pixel values of the first and second referenceable frames. 
     
     
         7 . The apparatus of  claim 6 , wherein pixel values of the at least one region within the predicted frame are interpolated from pixel values of the first and second referenceable frames using unequal interpolation weights. 
     
     
         8 . The apparatus of  claim 7 , wherein the unequal interpolation weights are determined based on a frame distance of each of the referenceable frames to the predicted frame. 
     
     
         9 . A decoder, the decoder being configured to process a sequence of coded frames in a bitstream, each frame comprising pixel values, wherein at least one region within a predicted frame is determined using pixel values from at least a first referenceable frame and a second referenceable frame, the first referenceable frame being prior to the second referenceable frame in decoding order and subsequent to the second referenceable frame in display order, wherein the predicted frame is prior to both the first and the second referenceable frames in display order, and wherein the bitstream comprises an expiration signal that identifies the first referenceable frame as expired, and in response to the expiration signal, the first referenceable frame is discarded as a candidate referenceable frame in decoding the bitstream. 
     
     
         10 . The decoder of  claim 9 , wherein the bitstream further comprises weighting signals, the weighting signals identifying interpolation weights to interpolate pixel values of the at least one region within the predicted frame from pixel values of the first and second referenceable frames. 
     
     
         11 . The decoder of  claim 10 , wherein the interpolation weights are unequal. 
     
     
         12 . The decoder of  claim 10 , wherein the interpolation weights are determined based on a frame distance of each of the referenceable frames to the predicted frame. 
     
     
         13 . The decoder of  claim 9 , wherein a signal transmitted from an encoder to the decoder within the bitstream identifies how to interpolate pixel values of the at least one region within the predicted frame from pixel values of the first and second referenceable frames. 
     
     
         14 . The decoder of  claim 13 , wherein pixel values of the at least one region within the predicted frame are interpolated from pixel values of the first and second referenceable frames using unequal interpolation weights. 
     
     
         15 . The decoder of  claim 14 , wherein the unequal interpolation weights are determined based on a frame distance of each of the referenceable frames to the predicted frame.