Image analysis – Image compression or coding – Adaptive coding
Reexamination Certificate
1999-11-24
2004-01-06
Do, Anh Hong (Department: 2624)
Image analysis
Image compression or coding
Adaptive coding
C382S242000, C382S243000, C382S250000
Reexamination Certificate
active
06674910
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for image-compression encoding and decoding using an adaptive transform, and more particularly to an apparatus and method for image-compression encoding and decoding using an adaptive transform in which, where different transform coefficients are outputted in accordance with a change of the transform direction order for an input image signal block, encoding and decoding procedures are conducted, based on the transform direction order selected in accordance with the characteristics of the input image signal block.
2. Description of the Prior Art
Among compression encoding schemes for digital images, the scheme most commonly used is a scheme in which every block of an image signal is transformed into a block having transform coefficients in accordance with an orthogonal transform method, and the transform coefficients are encoded. This scheme is widely used in a scheme proposed by Joint Technical Committee Joint Photographic Coding Experts Group (JPEG) of International Standardization Organization/International Electrotechnical Commission (ISO/IEC) JTC1/SC29/WG1, which is a compression encoding standardization scheme for still images, a scheme proposed by Moving Picture Experts Group (MPEG) of ISO/IEC, which is a compression encoding standardization scheme for moving images, and other international standardization schemes for digital compression encoding such as H.261 of International Telecommunication Union—Telecommunication Standardization Sector (ITU-T) and H.263 of ITU-T.
In accordance with conventional transform-based image signal compression techniques, every block of an input image signal is transformed into a block having transform coefficients in accordance with an orthogonal transform method. The transform coefficients are quantized, and then processed in accordance with a variable-length encoding method. The resultant signal is then transmitted to a decoder unit. In the decoder unit, the transmitted signal is decoded in accordance with processes inverse to those used in the encoding method, thereby recovering the original image signal. Referring to
FIG. 1
, a conventional image compression encoding and decoding system is illustrated. As shown in
FIG. 1
, the system mainly includes an encoding unit for encoding blocks of an input image signal using a compression technique, and a decoding unit for receiving an encoded signal outputted from the encoding unit, and conducting a decoding procedure, inverse to the encoding procedure, for the encoded signal, thereby recovering the original image signal.
The encoding unit includes a subtractor
1
for conducting a subtraction between an input image signal block and an image signal block, previously recovered, thereby outputting an residual signal block, and an overhead information encoder
9
for outputting an overhead information signal (for example, shape information) and a variable-length-coded shape information signal, which are to be used in the encoding procedure. The encoding unit also includes an orthogonal transform unit
2
for receiving the residual signal block from the subtractor
1
while selectively receiving the shape information from the overhead information encoder
9
in accordance with a switching operation conducted by a switch
10
b
, and performing a transform for the residual signal block based on the shape information in accordance with a specific transform method, thereby outputting a transform coefficient block, and a quantizer
3
for receiving the transform coefficient block from the orthogonal transform unit
2
, and quantizing the received transform coefficient block into a quantized transform coefficient block. The encoding unit further includes a variable-length encoder
8
for receiving the quantized transform coefficient block from the quantizer
3
, and encoding the received quantized transform coefficient block into a variable-length-coded transform coefficient signal, and a multiplexer
11
for receiving the variable-length-coded signal from the variable-length encoder
8
while selectively receiving the shape information from the overhead information encoder
9
in accordance with a switching operation conducted by a switch
10
a
, multiplexing the received signals together, and transmitting the resultant signal to a transmission medium
12
.
The encoding unit also includes a first inverse quantizer
4
for receiving the quantized transform coefficient block from the quantizer
3
, and conducting a inverse quantization for the received block, a inverse orthogonal transform unit
5
for receiving the inverse-quantized transform coefficient block from the first inverse quantizer
4
while selectively receiving the shape information from the overhead information encoder
9
in accordance with a switching operation of the switch
10
b
, and transforming the received block into a inverse-orthogonal-transformed signal block based on the shape information, an adder
6
a
for adding the previously recovered image signal block to the inverse-orthogonal-transformed signal block outputted from the inverse orthogonal transform unit
5
, thereby recovering the input image signal block, and a first memory
7
for receiving the recovered image signal block outputted from the adder
6
a
, and outputting it to the subtractor
1
as the previously recovered image signal block.
On the other hand, the decoding unit includes a demultiplexer (DEMUX)
13
for receiving the variable-length-encoded signal from the multiplexer
11
via the transmission medium
12
, thereby outputting a variable-length-encoded shape information signal and a variable-length-encoded input transform coefficient signal, a decoder
15
for decoding the variable-length-encoded coefficient signal into a quantized transform coefficient block, and a second inverse quantizer
16
for receiving the quantized transform coefficient block from the decoder
154
, and inverse quantizing the received block into a inverse-quantized transform coefficient block. The decoding unit also includes an overhead information decoder
14
for receiving the variable-length-encoded shape information from the demultiplexer
13
, and decoding the received shape information, thereby outputting recovered shape information, and a inverse orthogonal transform unit
17
for receiving the inverse-quantized transform coefficient block from the second inverse quantizer
16
while selectively receiving the shape information from the overhead information decoder
14
in accordance with a switching operation conducted by a switch
19
, and performing a inverse orthogonal transform for the received transform coefficient block based on the received shape information, thereby outputting a inverse-orthogonal-transformed signal block. The decoding unit further includes an adder
6
b
for adding an image signal block, previously recovered, to the inverse-orthogonal-transformed signal block outputted from the inverse orthogonal transform unit
17
, thereby outputting a recovered image signal block, and a second memory
18
for receiving the recovered image signal block outputted from the adder
6
b
, and outputting it to the adder
6
b
as the previously recovered image signal block.
The shape information is information for sorting an image into an object field and a background field. Such shape information makes it possible to allow a signal processing, associated with signal encoding and decoding, to be conducted based on the object field of an image, instead of the entire field of the image. Generally, shape information has the form of a binary mask consisting of pixels including object pixels and non-object pixels, that is, background pixels, having a value different from that of the object pixels.
Now, operations of the convention image compression-encoding and decoding system having the above mentioned configuration will be described.
When the subtractor
1
outputs an residual signal block after conducting a subtraction between an input image signal block and a r
Moon Joo-Hee
Park Cheol Soo
Song Joon Ho
Do Anh Hong
Hyundai Electronics Industries Co,. Ltd.
Lackenbach & Siegel LLP
Nissen J. Harold
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