US 5,267,334 A · Encoding/decoding moving images with forward and backward keyframes for forward and reverse display

Abstract

A method of removing frame redundancy in a computer system for a sequence of moving images. The method comprises detecting a first scene change in the sequence of moving images and generating a first keyframe containing complete scene information for a first image. The first keyframe is known, in a preferred embodiment, as a "forward-facing" keyframe or intra frame, and it is normally present in CCITT compressed video data. The process then comprises generating at least one intermediate compressed frame, the at least one intermediate compressed frame containing difference information from the first image for at least one image following the first image in time in the sequence of moving images. In a preferred embodiment, this at least one frame is known as an inter frame. Finally, detecting a second scene change in the sequence of moving images and generating a second keyframe containing complete scene information for an image displayed at the time just prior to the second scene change. This is known, in the preferred embodiment, as a "backward-facing" keyframe. The first keyframe and the at least one intermediate compressed frame are linked for forward play, and the second keyframe and the intermediate compressed frames are linked in reverse for reverse play. In a preferred embodiment, the intra frame is used for generation of complete scene information when the images are played in the forward direction. When this sequence is played in reverse, the backward-facing keyframe is used for the generation of complete scene information.

Claims20

Dependent claims

A method of encoding a first sequence of moving images as a second sequence of images in a computer system comprising:

a. detecting a first scene change in the first sequence of moving images and generating a first keyframe containing complete scene information for a first image detected at said first scene change in the first sequence of moving images for play of the second sequence of images in the forward direction;
b. generating at least one intermediate frame for the second sequence of images following said first keyframe, the at least one intermediate frame containing difference information from the first image for at least one image following the first image in time in the first sequence of moving images;
and
c. detecting a second scene change in the first sequence of moving images and generating a second keyframe following said at least one intermediate frame in the second sequence of images, said second keyframe containing complete scene information prior to the second scene change in the first sequence of moving images for play of the second sequence of images in reverse.

1 more element

A sequence of encoded images for representing a sequence of unencoded images, said sequence of encoded images which may be displayed in a forward direction and in a reverse direction, said sequence of encoded images comprising:

a. a first intra frame, said first intra frame establishing complete scene information for a first scene change of said unencoded sequence of images, said intra frame being first in said encoded sequence of images;
b. at least one inter frame, said at least one inter frame comprising difference information from said first intra frame for at least one second image in said unencoded sequence of images and following said first intraframe in said encoded sequence of images;
and
c. a second intra frame, said second intraframe comprising complete scene information for a frame prior to a second scene change of said unencoded sequence of images, said second intra frame following said at least one inter frame in said encoded sequence of images temporally, said first intra frame being displayed first during said forward display of said encoded sequence of images, followed by said at least one inter frame, and said second intra frame being displayed during said reverse display of said encoded sequence of images, said at least one inter frame following said second intra frame temporally during said reverse display of said encoded sequence of images.

1 more element

An apparatus for encoding a first sequence of unencoded images as a sequence of encoded images which may be displayed in a forward direction and a reverse direction comprising:

a. scene change detection means for determining when the difference between a frame and preceding frames of said unencoded sequence of images has exceeded a predetermined threshold;
b. forward keyframe creation means for creating a forward keyframe in said sequence of encoded images when a first scene change at a first frame has been detected in said unencoded sequence of images, said forward keyframe comprising complete scene information for said first frame of said unencoded sequence of images;
c. difference frame creation means for creating at least one difference frame following said forward keyframe in said encoded sequence of images from at least one second frame in said unencoded sequence of images following said first frame, said at least one difference frame comprising difference information between the forward keyframe and said at least one second frame in said unencoded sequence of images following said first frame;
d. reverse keyframe creation means for creating a reverse keyframe in said encoded sequence of images when a second scene change has been detected at a third frame in said unencoded sequence of images, said reverse keyframe comprising complete scene information for a fourth frame in said unencoded sequence of images, said fourth frame immediately preceding said third frame in said unencoded sequence of images;
and
e. linking means for linking said forward keyframe with said at least one difference frame in said encoded sequence of images for display of said encoded sequence of images in a forward direction, and further for linking said reverse keyframe with said at least one difference frame in said encoded sequence of images for display of said encoded sequence of images in a reverse direction.

3 more elements

Dependencies are inferred from the claim text.

Encoding/decoding moving images with forward and backward keyframes for forward and reverse display

Life of this patent

Encoding/decoding moving images with forward and backward keyframes for forward and reverse display

Life of this patent

Abstract

Claims20