Moving-picture coding and decoding method and apparatus with reduced computational cost
AssigneeOki Electric Industry Co., Ltd.
InventorZhixiong Wu
Life of this patent
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Abstract
A coded moving-picture signal is decoded by a resolution-converting motion compensation process and a resolution-converting inverse discrete cosine transform, both of which decrease the resolution of the picture, thereby reducing the amount of reference picture data that has to be stored and accessed. The reference picture data may also be stored in a compressed form. The resolution conversion and compression processes may also be used in the coding of the moving-picture signal. The resolution-converting inverse discrete cosine transform may be performed by output of intermediate results that have not been combined by addition and subtraction in a butterfly computation.
Claims64
A moving-picture decoder for decoding a coded moving-picture signal that has been coded by a discrete cosine transform with motion compensation and includes full-resolution motion vectors, comprising:
- a resolution-converting IDCT processor performing an inverse discrete cosine transform with resolution conversion on said coded moving-picture signal, thereby generating a first picture signal with reduced resolution;
- a resolution-converting motion compensator using said full-resolution motion vectors and a reduced-resolution reference picture signal to generate a second picture signal with reduced resolution;
- an adder coupled to said resolution-converting IDCT processor and said resolution-converting motion compensator, adding said first picture signal and said second picture signal to generate an output picture signal having reduced resolution;
- and
- a memory coupled to said adder and said resolution-converting motion compensator, storing said output picture signal for use as said reference picture signal.
A method of decoding a coded moving-picture signal that has been coded by a discrete cosine transform with motion compensation and includes full-resolution motion vectors, comprising the steps of:
- (a) performing an inverse discrete cosine transform with resolution conversion on said coded moving-picture signal, thereby generating a first picture signal with reduced resolution;
- (b) performing motion compensation, using said full-resolution motion vectors and a reduced-resolution reference picture signal, to generate a second picture signal with reduced resolution;
- (c) adding said first picture signal and said second picture signal to generate an output picture signal having reduced resolution;
- and
- (d) storing said output picture signal in a memory for use as said reference picture signal.
A moving-picture coder receiving a moving-picture signal as an input signal, comprising:
- a resolution-converting motion estimator comparing said moving-picture signal with a reference picture signal having reduced resolution, selecting one of predictive coding and intra-frame coding, and generating full-resolution motion vectors if said predictive coding is selected;
- a resolution-converting motion compensator coupled to said resolution-converting motion estimator, applying said full-resolution motion vectors to said reference picture signal and performing resolution conversion, thereby generating a first picture signal having full resolution and a second picture having said reduced resolution, when said predictive coding is selected;
- a subtractor coupled to said resolution-converting motion compensator, generating a third picture signal by subtracting said first picture signal from said input signal when said predictive coding is selected, said third picture signal being identical to said input signal when said intra-frame coding is selected;
- a DCT processor coupled to said subtractor, carrying out a discrete cosine transform on said third picture signal, thereby obtaining a transformed picture signal;
- a resolution-converting IDCT processor coupled to said DCT processor, carrying out an inverse discrete cosine transform and resolution conversion on said transformed picture signal, thereby obtaining a fourth picture signal having said reduced resolution;
- an adder coupled to said resolution-converting IDCT processor, adding said second picture signal and said fourth picture signal, thereby obtaining said reference picture signal;
- and
- a memory coupled to said adder, storing said reference picture signal.
A method of coding an input signal representing a moving picture, comprising the steps of:
- (a) comparing said moving-picture signal with a reference picture signal having reduced resolution, selecting one of predictive coding and intra-frame coding, and generating full-resolution motion vectors if said predictive coding is selected;
- (b) applying said full-resolution motion vectors to said reference picture signal and performing resolution conversion, thereby generating a first picture signal having full resolution and a second picture having said reduced resolution, when said predictive coding is selected;
- (c) generating a third picture signal by subtracting said first picture signal from said input signal when said predictive coding is selected, said third picture signal being identical to said input signal when said intra-frame coding is selected;
- (d) carrying out a discrete cosine transform on said third picture signal, thereby obtaining a transformed picture signal;
- (e) carrying out an inverse discrete cosine transform and resolution conversion on said transformed picture signal, thereby obtaining a fourth picture signal having said reduced resolution;
- (f) adding said second picture signal and said fourth picture signal, thereby obtaining said reference picture signal;
- and
- (g) storing said reference picture signal in a memory.
A moving-picture decoder for decoding a predictively coded moving-picture signal, comprising:
- a predictive decoding unit decoding said predictively coded moving-picture signal with reference to a reference picture signal, thereby obtaining an output picture signal;
- a data compressor coupled to said predictive decoding unit, compressively coding said output picture signal, thereby obtaining a compressed picture signal;
- a memory coupled to said data compressor, storing said compressed picture signal;
- and
- a data decompressor coupled to said memory, expanding said compressed picture signal, thereby obtaining said reference picture signal.
A method of decoding a predictively coded moving-picture signal, comprising the steps of:
- (a) decoding said predictively coded moving-picture signal with reference to a reference picture signal, thereby obtaining an output picture signal;
- (b) compressively coding said output picture signal, thereby obtaining a compressed picture signal;
- (c) storing said compressed picture signal in a memory;
- and
- (d) expanding said compressed picture signal, thereby obtaining said reference picture signal.
A one-dimensional inverse discrete cosine transform processor operating in a first mode with full resolution and a second mode with reduced resolution, comprising:
- a first multiply-accumulate processor performing a first matrix operation on a first input signal, obtaining first intermediate results;
- a second multiply-accumulate processor performing a second matrix operation on said first input signal in said first mode, and performing said first matrix operation on a second input signal in said second mode, obtaining second intermediate results;
- a first butterfly processor coupled to said first multiply-accumulate processor and said second multiply-accumulate processor, combining said first intermediate results with said second intermediate results by addition and subtraction, thereby obtaining combined results;
- and
- a selector coupled to said first butterfly processor, selecting said combined results for output in said first mode, and selecting said first intermediate results and said second intermediate results for output in said second mode.
A method of performing a one-dimensional inverse discrete cosine transform in a first mode with full resolution and a second mode with reduced resolution, comprising the steps of:
- (a) performing a first matrix operation on a first input signal, obtaining first intermediate results;
- (b) performing a second matrix operation on said first input signal in said first mode, and said first matrix operation on a second input signal in said second mode, obtaining second intermediate results;
- (c) combining said first intermediate results with said second intermediate results by addition and subtraction, thereby obtaining combined results;
- (d) selecting said combined results for output in said first mode;
- and
- (e) selecting said first intermediate results and said second intermediate results for output in said second mode.
Dependencies are inferred from the claim text.