Device and method for variable length coding of video signals depending on the characteristics
First Claim
1. An apparatus for compressing and expanding a video signal, comprising:
- motion estimation means having an input terminal for estimating a motion in the video signal inputted through the input terminal and generating a notion vector signal;
motion compensation means for compensating for the motion in the video signal in response to the motion vector signal;
subtraction means for subtracting an output signal of said motion compensation means from the video signal to output a difference signal;
discrete cosine transform means for performing a discrete cosine transform with respect to the difference signal from said subtraction means to remove spatial redundancy;
quantization means for compressing output information from said discrete cosine transform means, the output information from said discrete cosine transform means being approximated to a finite number of values to reduce an amount of the output information from said discrete cosine transform means;
inverse quantization means for restoring an output signal from said quantization means to an original state;
inverse discrete cosine transform means for transforming an output signal from said inverse quantization means to a spatial signal;
adding means for adding an output signal from said inverse discrete cosine transform means to the output signal from said motion compensation means and feeding back a resultant signal to said motion compensation means;
first mapping means for outputting information corresponding to the output signal from said quantization means;
scene change detection means for detecting a scene change in the video signal inputted through the input terminal;
variable length coder control means for stopping a learning occurring after the scene change and performing a new learning for a predetermined time period and allowing an optimum symbol to correspond to a given codebook, the variable length coder control means comparing a bit amount generated using the optimum symbol with a bit amount generated using an existing symbol in response to a scene change detect signal from said scene change detection means and a statistical characteristic of said changed scene, the variable length coder control means outputting a new symbol when a gain is present in accordance with a result of comparison of the bit amounts;
second mapping means for outputting information corresponding to said new symbol from said variable length coder control means;
first multiplexing means for selectively outputting the output information from one of said first and second mapping means;
variable length coder means for reducing an amount of the output information from said first multiplexing means without losing a characteristic of the output information from said first multiplexing means;
first buffering means for preventing one of an underflow and an overflow of an output signal from said variable length coder means resulting from transmission at a fixed bit rate; and
formatting means for formatting an output signal from said first buffering means to a suitable transmission format.
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Abstract
An apparatus and a method of compressing and expanding a video signal. The apparatus includes a variable length coder controller and a quantizer. The coder controller compares a bit amount generated in the use of an optimum symbol with that in the use of an existing symbol upon detection of a scene change and outputs a new symbol upon the presence of a gain in accordance with the compared result. A frame delay delays input image data in a unit frame, a subtracter for subtracting an output signal of the frame delay from the input image data, and a scene change detector for detecting a scene change of the input image data. A motion detector detects a motion in the input image data, a main codebook for forming variable sub-codebooks for a still picture, a codebook controller for selecting a specified portion of the main codebook and variable sub-codebooks, and a vector formation unit for forming the input image data into a vector. A distortion measurement unit obtains a codeword with a minimum distortion using the variable sub-codebooks if the input image data is the still picture and using the main codebook if the input image data is a motion picture, and a code assignment unit for assigning a proper code to an output signal from the distortion measurement unit.
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Citations
9 Claims
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1. An apparatus for compressing and expanding a video signal, comprising:
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motion estimation means having an input terminal for estimating a motion in the video signal inputted through the input terminal and generating a notion vector signal; motion compensation means for compensating for the motion in the video signal in response to the motion vector signal; subtraction means for subtracting an output signal of said motion compensation means from the video signal to output a difference signal; discrete cosine transform means for performing a discrete cosine transform with respect to the difference signal from said subtraction means to remove spatial redundancy; quantization means for compressing output information from said discrete cosine transform means, the output information from said discrete cosine transform means being approximated to a finite number of values to reduce an amount of the output information from said discrete cosine transform means; inverse quantization means for restoring an output signal from said quantization means to an original state; inverse discrete cosine transform means for transforming an output signal from said inverse quantization means to a spatial signal; adding means for adding an output signal from said inverse discrete cosine transform means to the output signal from said motion compensation means and feeding back a resultant signal to said motion compensation means; first mapping means for outputting information corresponding to the output signal from said quantization means; scene change detection means for detecting a scene change in the video signal inputted through the input terminal; variable length coder control means for stopping a learning occurring after the scene change and performing a new learning for a predetermined time period and allowing an optimum symbol to correspond to a given codebook, the variable length coder control means comparing a bit amount generated using the optimum symbol with a bit amount generated using an existing symbol in response to a scene change detect signal from said scene change detection means and a statistical characteristic of said changed scene, the variable length coder control means outputting a new symbol when a gain is present in accordance with a result of comparison of the bit amounts; second mapping means for outputting information corresponding to said new symbol from said variable length coder control means; first multiplexing means for selectively outputting the output information from one of said first and second mapping means; variable length coder means for reducing an amount of the output information from said first multiplexing means without losing a characteristic of the output information from said first multiplexing means; first buffering means for preventing one of an underflow and an overflow of an output signal from said variable length coder means resulting from transmission at a fixed bit rate; and formatting means for formatting an output signal from said first buffering means to a suitable transmission format. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for variable length coding of a video signal depending on image characteristics using image compression coding means which are comprised of well-known devices and operating functions including discrete cosine transform, quantization, motion compensation, motion estimator, inverse discrete cosine transform, and inverse quantization, the apparatus comprising
scene change detection means for detecting a scene change in the video signal inputted through an input terminal; -
variable length coder control means for stopping a learning occurring after the scene change and performing a new learning for a predetermined time period and allowing an optimum symbol to correspond to a given codebook, the variable length coder control means comparing a bit amount generated using the optimum symbol with a bit amount generated using an existing symbol in response to a scene change detect signal from said scene change detection means and a statistical characteristic of said changed scene, the variable length coder control means outputting a new symbol when a gain is present in accordance with a result of comparison of the bit amounts; first mapping means for outputting information corresponding to an output signal from image compression coding means; second mapping means for outputting information corresponding to said new symbol from said variable length control means; multiplexing means for selectively outputting the output information from one of said first and second mapping means; and variable length coder means for reducing an amount of the output information from said multiplexing means without losing a characteristic of the output information from said multiplexing means.
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7. An apparatus for expanding a video signal in response to a received video compression signal, the apparatus comprising:
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deformatting means for deformatting an output signal from said received video compression signal to a suitable reception format; buffering means for adjusting a number of bits of an output signal from said deformatting means at a desired rate; shifting means for shifting an output signal from said buffering means; programmable logic array means connected to an output; of said shifting means, said programmable logic array means storing a predetermined codeword; first mapping means for outputting information corresponding to the predetermined codeword in said programmable logic array means; control means, responding to the output signal from said deformatting means for determining, whether to use one of a new codeword or the predetermined codeword, the control means outputting a select control signal in accordance with a determination result; second mapping means for outputting information corresponding to the new codeword; and multiplexing means for selectively outputting the output information from one of said first and second mapping means in response to the select control signal from said control means.
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8. An apparatus for compressing and expanding a video signal, comprising:
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motion estimation means having an input terminal for estimating a motion in the video signal inputted through the input terminal and generating a motion vector signal; motion compensation means for compensating for the motion in the video signal in response to the motion vector signal; subtraction means for subtracting an output signal of said motion compensation means from the video signal to output a difference signal; discrete cosine transform means for performing a discrete cosine transform with respect to the difference signal from said subtraction means to remove spatial redundancy; vector quantization means for compressing output information from said discrete cosine transform means, the output information from said discrete cosine transform means being approximated to a finite number of values to reduce an amount of the output information from said discrete cosine transform means; inverse vector quantization means for restoring an output signal from said quantization means to an original state; inverse discrete cosine transform means for transforming an output signal from said inverse vector quantization means to a spatial signal; adding means for adding an output signal from said inverse discrete cosine transform means to the output signal from said motion compensation means and feeding back a resultant signal to said motion compensation means; first mapping means for outputting information corresponding to the output signal from said quantization means; scene change detection means for detecting a scene change in the video signal inputted through the input terminal; variable length coder control means for comparing a bit amount generated using the optimum symbol with a bit amount using an existing symbol in response to a scene change detect signal from said scene change detection means, the variable length coder control means outputting a new symbol when a gain is present in accordance with a result of comparison of the bit amounts; second mapping means for outputting information corresponding to a new codeword from said variable length control means; first multiplexing means for selectively outputting the output information from one of said first and second mapping means; variable length coder means for reducing an amount of the output information from said first multiplexing means without losing a characteristic of the output information from said first multiplexing means; first buffering means for preventing one of an underflow and an overflow of an output signal from said variable length coder means resulting from transmission at a fixed bit rate; and formatting means for formatting an output signal from said first buffering means to a suitable transmission format. - View Dependent Claims (9)
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Specification