Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-12-17
2003-09-02
Philippe, Gims S. (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C382S236000, C348S416100
Reexamination Certificate
active
06614846
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods for low-efficiency-encoding and -decoding and transmitting two types of image signals which have different resolution or progressive scanning signals, and methods for recording and reproducing these signals on and from an optical disc, as well as apparatuses for realizing these methods.
BACKGROUND ART
At present MPEG2 is standardized as a method for applying high-efficiency-encoding TV signals. MPEG2 is characterized in that it enables high-image-quality recording and transmission at a relatively low data rate and in that it enables compression to various data rates. One method according to MPEG2 executes encoding and decoding using the correlationship between high-resolution signals and low-resolution signals.
This encoding method executes encoding by detecting motion vectors using as a reference frame a high-resolution image or an image obtained by increasing the resolution of an image obtained by encoding and decoding a low-resolution signal. The above decoding method executes decoding with applying motion compensation using as a reference frame both a decoded high-resolution image and an image obtained by increasing the resolution of a decoded low-resolution image.
According to such conventional encoding and decoding methods, if the reference image for the motion vector is changed from a low-resolution signal to an up-convert image, the motion vector becomes less accurate. In addition, since a high-resolution signal is directly encoded, the data rate increases during encoding. In addition, due to the complexity of the encoding method, the decoding method is also complicated, resulting in the need to increase the size of a circuit for realizing both methods.
MPEG2 also defines a method for transmitting a signal obtained by encoding a high-resolution signal using the correlationship between this signal and a low-resolution signal. This method multiplexes a high-resolution signal and a low-resolution signal which have been low-efficiency-encoded before transmitting these signals.
According to a transmission apparatus for realizing such a conventional transmission method, if the broadcasting of high-resolution signals is started, viewers having a conventional decoder compatible with low-resolution signals cannot view the broadcasting.
In addition, when MPEG2 encodes progressive scanning signals, it uses as an input image to encode, a 4:2:0p signal (hereafter referred to as a “
420
p signal”) that is obtained by down-sampling color difference signals of the progressive scanning signals.
On the other hand, there is another type of 4:2:0p signal defined by SMPTE294M that is a transmission standard as the 4:2:0p signal obtained by down-sampling color difference signals for progressive scanning signals. Both signals are obtained by down-sampling color difference signals of progressive scanning signals, but have different color-difference-signal sampling positions relative to a luminance signal. Thus, to use MPEG2 to encode a
420
p signal transmitted using SMPTE294M, an input signal must be up-converted to an
844
signal and then down-converted to a
420
p signal of the phase of a color difference signal according to the MPEG standard, followed by MPEG compression. On the contrary, to use SMPTE294M to decode and transmit a 4:2:0p signal that has been MPEG2-compressed, a decoded signal must be up-converted to an
844
signal and then down-converted to a
420
p signal of the phase of a color difference signal according to the SMPTE294M standard, followed by transmission.
According to such conventional image-signal encoding, decoding, and transmission methods and apparatuses using these methods, a color difference signal is converted twice between the apparatuses and may thus be degraded.
In addition, data encoded using the MPEG2 method is recorded on an optical disc for dense recording that is called a digital video disc (hereafter referred to as a “DVD”). At present, only NTSC- or PAL-based image signals that are interlaced scanning signals are recorded on a DVD, and progressive scanning signals that are image signals having more vertical scanning lines than the NTSC- or PAL-based signals have not been put to practical use yet.
When progressive scanning signals encoded using MPEG2 are recorded on a conventional optical disc, twice as many pixels as in interlaced scanning signals are required to force the data rate of a resulting bit stream to be increased. Such a high data rate may not be dealt with by the existing optical-disc standards. In addition, commercially available apparatuses cannot decode (playback) progressive image signals that have been recorded on an optical disc within a single stream, and this is inconvenient to users.
DISCLOSURE OF THE INVENTION
It is an object of this invention to provide an encoding apparatus for accurately determining motion vectors to encode two types of image signals of different resolutions and a decoding apparatus for decoding signals encoded by the encoding apparatus.
To achieve the above-mentioned object, the present invention is an image signal encoding apparatus comprising
a motion vector detecting means for detecting motion vectors using a first image signal of a high resolution, a resolution reducing means for creating a second image signal of a low resolution from said first image signal, an image signal interpolating means for interpolating said second image signal in such a way as to have the same number of pixels as said first image signal, thereby creating an interpolated signal, a differential means for determining the differential between said first image signal and said interpolated signal to create a differential signal, and
an encoding means for using said motion vectors to low-efficiency-encode said differential signal.
Further, the present invention is an image signal encoding apparatus comprising, a motion vector detecting means for detecting motion vectors using a first image signal of a high resolution, a resolution reducing means for creating a second image signal of a low resolution from said first image signal, a second encoding means for encoding said second image signal to create a second encoded signal, a second decoding means for decoding said second encoded signal to create a second decoded signal, an image signal interpolating means for interpolating said second decoded signal in such a way as to have the same number of pixels as said first image signal, thereby creating an interpolated signal, a differential means for determining the differential between said first image signal and said interpolated signal to create a differential signal, and a first encoding means for using said motion vectors to low-efficiency-encode said differential signal.
This configuration can accurately determine motion vectors and reduce the data rate after encoding by encoding differential signals.
Further, the present invention is an image signal decoding apparatus comprising a first decoding means for decoding a first stream obtained by encoding a high-resolution signal to obtain a first image signal, a second decoding means for decoding a second stream obtained by encoding a low-resolution signal to obtain a second image signal, an image signal interpolating means for interpolating said second image signal in such a way as to have the same number of pixels as said first image signal, thereby creating an interpolated signal, and an adding means for adding said first image signal and said interpolated signal to create a decoded signal for said high-resolution signal.
This configuration can use a simple circuit configuration to provide a decoding apparatus for signals encoded by the present encoding apparatus.
It is also an object of this invention to provide an image-signal transmission apparatus that enables viewers having a decoder for low-resolution signals to view broadcasting.
To achieve the above-mentioned object, the present invention is an image signal transmission apparatus comprising a dividing means for dividing an input image signal into a first image signal of a
Fujiwara Yuji
Ide Akifumi
Kobayashi Masa-aki
Matsuda Toyohiko
Nagaoka Yoshitomi
Matsushita Electric - Industrial Co., Ltd.
RatnerPrestia
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