Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-06-13
2001-07-24
Rao, Andy (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240150
Reexamination Certificate
active
06266372
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reproducing apparatus and, more particularly, to an image reproducing apparatus for concealing undecodable data of a video signal which was high efficiently encoded and for reproducing such data.
2. Related Background Art
An orthogonal transformation encoding method is known as a technique for highly efficiently compressing and encoding an image signal. According to such a method, after the image signal has been divided into blocks every predetermined number of pixels in a lump, an orthogonal transformation such as a discrete cosine transformation (DCT) or the like is executed. A quantization, an entropy encoding or the like is executed on coefficients after completion of the transformation.
According to such a method, since the encoding is executed on a block unit basis, when an error occurs in the encoding data, a code error occurs on a block unit basis. Since a variable length code is frequently used, a decoding error is propagated over a plurality of blocks, so that it results in a large deterioration of the image.
An interframe interpolation in which an error block is replaced by the image of a previous frame is known as a means for obtaining a reproduction image by interpolating and concealing such an error block.
FIG. 1
shows a concealing operation by interframe interpolation. Now, assuming that a block X of a frame #n cannot be reproduced, the interframe interpolation is realized by replacing the data of the block X by the reproduction data of a block A′ at the same position on a screen of a previous frame #n-
1
and by reproducing the data.
According to such an interframe interpolation, however, when a movement of an image is hard, the interpolation data is deviated from the image data of a peripheral block in the same field with respect to the time and differs from the image data. Therefore, when the data of the error block is replaced by the interpolation data, it becomes a visually large obstruction.
A method of using image data in the same field as interpolation data is also considered. In this case, however, although there is a correlation as compared with that of the interframe interpolation with regard to the time, a correlation is contrarily low with respect to the space.
Therefore, there is also considered a method whereby a movement of an unreproducible block is estimated by the image data of an upper block of the unreproducible block. The interframe interpolation and the intrafield interpolation are switched in accordance with the movement. In this case, however, since the movement of the unreproducible block is estimated by only the image data of the upper block, it is likely to erroneously estimate the movement and there is a possibility that the error data is interpolated by data of a low correlation.
SUMMARY OF THE INVENTION
Under such circumstances, it is an object of the invention to solve the problems mentioned above.
Another object of the invention is to provide an image reproducing apparatus which can obtain an image in which the deterioration of eyesight is small by raising the precision of a movement estimation of an undecodable block.
Under such objects, according to the present invention, as one embodiment, there is provided an image reproducing apparatus comprising: (a) reproducing means for reproducing an image signal which was block encoded from a recording medium; (b) decoding means for decoding the image signal reproduced by the reproducing means; (c) movement detecting means for detecting movement of each of a plurality of blocks around a block including the image signal which cannot be decoded by the decoding means and for outputting; and (d) constructing means for constructing an image signal for the image signal of the block including the undecodable image signal on the basis of a plurality of outputs of the movement detecting means.
Still another object of the invention is to obtain a good image even in the case where movement information from a plurality of blocks around an undecodable block differs.
Under such an object, according to the invention, as one embodiment, there is provided an image processing device comprising: (a) input means for inputting an image signal which was divided into blocks; (b) movement detecting means for detecting the presence or absence of a movement of each of the plurality of blocks; and (c) concealing means for concealing a target block by using another block on the basis of an output of the movement detecting means, wherein in the case where the result of the detection of the movement detecting means differs, the concealing means divides the target block into a plurality of portions and can execute different concealing processing on each of the plurality of portions.
The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings.
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Niida Mitsuo
Shimizu Tetsuya
Canon Kabushiki Kaisha
Rao Andy
Robin Blecker & Daley
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