Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1997-11-12
2003-07-01
Rao, Andy (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240260, C375S240230
Reexamination Certificate
active
06587509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a moving image decoding method and a moving image decoding apparatus, and more particularly, is suitable for use in reproducing moving image signals recorded on a recording medium such as an optical disk, a magnetic tape, or the like to display reproduced moving images on a display unit, or suitable for use in a television conference system, a television telephone system, broadcasting equipment, and so on, wherein moving image signals are transmitted through transmission channels from the transmission side to the reception side such that the reception side receives the moving image signals to display.
2. Description of the Related Art
A system for transmitting moving image signals to remote locations, such as a television conference system, a television telephone system, digital TV broadcasting, and so on, utilizes a line correlation and inter-frame correlation of video signals to compress the moving image signals for encoding in order to efficiently utilize transmission channels. The configuration of a moving image encoding/decoding apparatus for encoding moving image signals for transmission and for decoding transmitted moving image signals is shown in FIG.
1
. An encoding unit
1
encodes an input video signal VD and transmits the encoded video signal to a recording medium
3
as a transmission channel. A decoding unit
2
reproduces signals recorded on the recording medium
3
, and decodes and outputs the reproduced signals.
In the encoding unit
1
, the input video signal VD is inputted to a pre-processing circuit
4
. The pre-processing circuit
4
separates the input video signal VD into a luminance signal and a color (color difference signal in this case) signal and supplies the luminance signal and the color signal to A/D (analog-to-digital) convertors
5
,
6
, respectively. The A/D convertors
5
,
6
convert the luminance signal and the color signal being analog signals into respective digital signals. The luminance signal and the color signal which are converted into digital signals are supplied to a pre-filter
7
. The pre-filter
7
performs filtering processing to the inputted digital signals, and then supplies the digital signals on a frame memory
8
. The frame memory
8
stores the luminance signal in a luminance signal frame memory
8
A and the color difference signal in a color difference signal frame memory
8
B, respectively.
The pre-filter
7
performs processing for increasing an encoding efficiency and for improving an image quality. This may be, for example, a filter for removing noise, or a filter for limiting a bandwidth.
FIG. 2
shows the configuration of a two-dimensional low pass filter as an example of the pre-filter
7
. In
FIG. 2
, a reference letter D designates a one-pixel delay. Also,
FIG. 3A
shows filter coefficients for this two-dimensional low pass filter, and
FIG. 3B
shows a 3×3 pixel block which is inputted to the filter. For an objective pixel e, the two-dimensional low pass filter extracts a block of 3×3 pixels around the pixel e. The two-dimensional low pass filter performs the following mathematical operation for the extracted pixel block.
{fraction (1/16)}
×a+
⅛
×b+
{fraction (1/16)}
×c+
⅛
×d+
¼
e+
⅛
×f+
{fraction (1/16)}
×g+
⅛
×h+
{fraction (1/16)}
×i
(1)
The output of this mathematical operation is used as an output value of the filter for the pixel e. Actually, in the pre-filter
7
, filtered output values are delivered from an output OUT
1
, while original pixel values unfiltered are delivered from an output OUT
2
after a predetermined amount of delay. In this filter, uniform filtering is always performed irrespective of inputted image signals and irrespective of a state of an associated encoder.
A format convertor
9
converts an image signal stored in the frame memory
8
to data of a predetermined format suitable for inputting to an encoder
10
. The data converted to the predetermined format is supplied from the format convertor
9
to the encoder
10
, where the data is encoded. An encoding algorithm used herein is arbitrary, an example of which will be described later. The signal encoded by the encoder
10
is outputted therefrom as a bit stream which is recorded, for example, on a recording medium
3
.
Data reproduced from the recording medium
3
is supplied to a decoder
11
in the decoding unit
2
for decoding. While a decoding algorithm used in the decoder
11
is arbitrary, it must correspond to the encoding algorithm. An example of the decoder
11
will be described later. The data decoded by the decoder
11
is inputted to a format convertor
12
, where it is converted to an output format.
A luminance signal separated from an image signal in the frame format is supplied to and stored in a luminance signal frame memory
13
A in a frame memory
13
, while a color difference signal is supplied to and stored in a color difference signal frame memory
13
B. The luminance signal and the color difference signal respectively read from the luminance signal frame memory
13
A and the color difference signal frame memory
13
B are supplied to a post-filter
14
for filtering, and then supplied to D/A convertors
15
,
16
. The D/A convertors
15
,
16
convert the supplied luminance signal and color difference signal being digital signals into analog signals respectively, and supply the luminance signal and the color signal which are converted into analog signals to a post-processing circuit
17
. Then, the post-processing circuit
17
mixes the supplied luminance signal and color signal with each other. The output video signal is outputted to a display unit (not shown) which may be, for example, a CRT display or the like, and displayed thereon.
The post-filter
14
executes filtering for improving the image quality to alleviate a deteriorated image caused by the encoding. The post-filter
14
may be, for example, a filter for removing block distortion, noise generated near abrupt edges, quantization noise, and so on. While a variety of post-filters are available, a two-dimensional low pass filter similar to that used for the pre-filter
7
, as shown in
FIG. 2
, may be utilized by way of example.
Next, the highly efficient encoding of moving images will be explained. Since moving image data such as video signals or the like contains an extremely large amount of information, an extremely high data transmission speed is required for recording and/or reproducing the moving image data on a recording medium for a long time period. This leads to a requirement of a large magnetic tape or optical disk. Also, even when moving image data is communicated through a transmission channel or used for broadcasting, such an excessively large amount of data causes a problem that existing transmission channels cannot be utilized for communications of the moving image data as it is.
Therefore, for recording video signals on a much smaller recording medium for a long time period or for utilizing video signals for communications and broadcasting, means is indispensable for very efficiently encoding the video signals for recording and for very efficiently decoding read signals which have been encoded. To meet such requirements, highly efficient encoding schemes, utilizing a correlation of video signals, have been proposed, one of which is the MPEG (Moving Picture Experts Group) scheme. This scheme has been discussed and proposed as a standard in ISO-IEC/JTC1/SC2/WG11. Specifically, the MPEG scheme is a hybrid scheme which includes a combination of a motion compensation predictive encoding and a discrete cosine transform (DCT) coding. As an example, the MPEG scheme has been proposed by the present applicant in the specification and the drawings of U.S. application U.S. Pat. No. 5,155,593 (Date of Patent: Oct. 13, 1992).
The motion compensation predictive encoding is a method which utilizes a correlation of
Suzuki Teruhiko
Yagasaki Yoichi
Frommer William S.
Frommer & Lawrence & Haug LLP
Rao Andy
Sony Corporation
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