Computer graphics processing and selective visual display system – Display driving control circuitry – Controlling the condition of display elements
Reexamination Certificate
2000-02-15
2001-04-17
Black, Thomas (Department: 2171)
Computer graphics processing and selective visual display system
Display driving control circuitry
Controlling the condition of display elements
C386S349000, C386S349000, C382S309000
Reexamination Certificate
active
06219043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to encoding systems in which a section of an encoded bitstream is replaced with a new section, and is more particularly related to video encoding systems in which a section of encoded video is replaced in a manner which reduces decoding artifacts.
2. Discussion of the Background
Before compression schemes became available, audio, video, and film could be simply edited by cutting out a section of the audio, video, or film and replacing it with a new or altered section, as desired. However, with the use of compression schemes to encode data, a simple “cut-and-paste” editing procedure may no longer be possible as the information used to construct a frame of video, for example, is at more than one location. Therefore, simply cutting out a section of encoded video may degrade sections of the video which have been unaltered and the new video may contain decoding artifacts if simply inserted into the previously encoded bitstream.
A known solution to this problem in MPEG video encoding is to label a new section of video which is substituted into the old video as being a closed Group Of Pictures (GOP). In MPEG encoding, a closed group of pictures indicates that the predictions used in the B-type frames immediately following the first coded I frame is to use only backward prediction. Alternatively, MPEG allows the use of a flag called “broken_link” which when set indicates that the first B-frames immediately following the first coded I-frame may not be correctly decoded because the reference frame which is used for prediction is not available. The decoder uses this flag to avoid displaying frames that cannot be correctly decoded.
The above solutions will degrade the encoded video and may provide inadequate video quality.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a novel method and system in which a section of previously encoded data is replaced with another section of encoded data while introducing minimal or no visible decoding artifacts. It is a further object of the invention to provide a video encoding system which allows a section of encoded video to be replaced by another section of encoded video so that no errors or video decoding artifacts are visible in the encoded video. It is yet another object of the invention to provide a memory containing data structures for storing information in a novel and useful manner.
These and other objects are accomplished by a novel method and system to replace section of an encoded bitstream. In order to remove a section of the encoded video, it is necessary to determine the beginning and ending points of the encoded video in the digitally encoded bitstream. This is performed by summing up the number of bits used for each previously encoded frame in order to determine the bit offset for the picture in question. Alternatively, a directory could be used to maintain information indicating the exact location of a specific frame or time period in the encoded bitstream.
A first section, for example one GOP which is one half of a second, of the original video is placed at the beginning of the new video to be encoded and is used to create the last P-frame of a GOP before a cut point which is needed to properly encode and decode the first two B-frames of a subsequent GOP. The encoded data from this short initial section is not substituted into the previously encoded data but is used only to create the reference frame (last P-frame) which is referenced by the first two B-frames after the start point.
Also, a short section of the original video is placed at the end of the video and encoded using the quantizer values used when originally encoded. Because frames of encoded video in a GOP refer back to previous encoded frames, if a frame of the original encoding referred back to a new frame of video immediately before the end point, there would be a decoding glitch. Therefore, it is desirable for the original video to refer back to a frame which is equivalent to the original frame. It is to be noted that one second of the original video is also re-encoded at the beginning of the edit segment, but this is not essential.
As an alternative, the substitute video is encoded using the known closed group of pictures mode so that frames in the substitute video do not depend on frames outside of the substitute video. A novel aspect of this method is that extra bits are allocated for the bidirectional frames which will only have single direction prediction because of the closed GOP mode so that the number of bits of the B-frame approximates the number of bits used for a P-frame. In this manner, the closed GOP mode does not induce large decoding artifacts for the B-frames but the B-frames have approximately the same quality as a P-frame.
The encoded video stored on a digital storage medium also constitutes part of the invention. The invention also includes a memory for storing novel and useful data structures. The memory is preferably an optical disc.
REFERENCES:
patent: 5347310 (1994-09-01), Yamada et al.
patent: 5577191 (1996-11-01), Bonomi
patent: 6026232 (2000-02-01), Yogeshwar et al.
Cookson Christopher J.
Ichikawa Teiichi
Kitamura Tetsuya
Mimura Hideki
Ng Sheau-Bao
Black Thomas
Kabushiki Kaisha Toshiba
Loomis John C.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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