Television – Bandwidth reduction system – Data rate reduction
Reexamination Certificate
1999-07-12
2001-06-12
Lee, Young (Department: 2713)
Television
Bandwidth reduction system
Data rate reduction
C348S404100
Reexamination Certificate
active
06246438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image coded data re-encoding apparatus for producing a second image coded data by applying digital signal processing to a first image coded data which is obtained by coding a digital input image signal.
2. Description of Related Art
FIG. 16
is a block diagram showing a conventional image coded data re-encoding apparatus disclosed in Japanese patent application laid-open No. 2-179186/1990, for example. It is an example of a multiple site video conference system. In this figure, the reference numeral
1
designates a master station,
2
designates a relay station,
3
designates a slave station,
10
designates an image coder of the stations, and
20
designates an image decoder. The reference numerals
101
designates an input image,
102
designates image coded data,
103
designates a decoded image signal,
104
designates image re-encoded data, and
105
designates a decoded image signal.
The operation will now be described.
The image coder
10
of the master station
1
performs coding of the input image
101
, and sends the image coded data
102
to the relay station
2
. The relay station
2
receives the image coded data
102
with its image decoder
20
to decode it, and generates the image re-encoded data
104
by re-encoding the decoded image signal
103
with the image coder
10
. The image re-encoded data
104
thus generated by the re-encoding is transmitted to the slave station
3
. The slave station
3
decodes with the image decoder
20
the image re-encoded data
104
which is relayed through the relay station
2
, and uses it as the decoded image signal
105
.
When holding a conference using the relay station
2
with such a decoding and relaying function, it often occurs that the master station
1
and the slave station
3
employ different coding systems. In this case, it becomes necessary to change the amount of coded data to be generated and various types of parameters such as image size and a frame rate. Thus, the relay station
2
once decodes the received image coded data
102
into the decoded image signal
103
, and then re-encodes it into the image re-encoded data
104
, thereby matching the different coding systems.
In this way, the conventional image coded data re-encoding apparatus has a process through which the image coded data is once decoded to be re-encoded to achieve relaying or copying of the image coded data.
Since the conventional image coded data re-encoding apparatus with such an arrangement once decodes the image coded data
102
into the decoded image signal
103
, and then re-encodes the decoded image signal
103
regardless of its contents to relay or convert the image coded data
102
, it has some problems such as degrading the image quality of the decoded image signal
105
, increasing a delay involved in the relay and transform, and augmenting the size of the apparatus.
SUMMARY OF THE INVENTION
The present invention is accomplished to solve such problems, and to provide an image coded data re-encoding apparatus which can reduce the image degradation, shorten the processing delay, and shrink the device size, thereby achieving an efficient transform of the image coded data.
According to one aspect of the present invention, there is provided an image coded data re-encoding apparatus comprising: an image coded data analyzer for generating coded data after signal processing by performing a first digital signal processing on a first image coded data; and an image coded data synthesizer for generating a second image coded data by performing on the coded data after signal processing a second digital signal processing based on multiple signals associated with a first image coded data by using the coded data after signal processing output from the image coded data analyzer and the multiple signals.
This will offer an advantage of reducing the degradation of the image quality after the transform, decreasing processing delay, and achieving an image coded data re-encoding apparatus with a reduced size in comparison with a system in which the first image coded data is always once decoded into a decoded image, followed by re-encoding of the decoded image into the second image coded data regardless of the decoded data.
In image coded data re-encoding apparatus, the image coded data analyzer may extract the multiple signals in the course of generating the coded data after signal processing by performing the first digital signal processing on the first image coded data, and may provides the image coded data synthesizer with the coded data after signal processing.
This will offer an advantage of providing an information effective image coded data re-encoding apparatus capable of obviating special additional information which was needed for the second digital signal processing for generating the second image coded data.
In the image coded data re-encoding apparatus, the image coded data re-encoding apparatus may further comprise a separator for separating from the first image coded data the multiple signals which have been externally combined with the first image coded data and cannot be extracted from the first image coded data in the first digital signal processing for generating the coded data after signal processing, and the image coded data synthesizer may generate the second image coded data by using the multiple signals output from the separator.
This will offer an advantage of providing a coded data re-encoding apparatus which can use, in the second digital signal processing for generating the second image coded data, information which cannot be extracted in course of the first digital signal processing, and this will make possible more effective transform than when such information is not used.
The image coded data re-encoding apparatus may further comprise an information extractor/estimator for extracting or estimating the multiple signals needed for the second digital signal processing from the coded data after signal processing generated by the image coded data analyzer, and the image coded data synthesizer may generate the second image coded data by using the multiple signals output from the information extractor/estimator.
This will offer an advantage of providing an image coded data re-encoding apparatus with a simple configuration because it obviates special processing involved in decoding.
In the image coded data re-encoding apparatus, the image coded data synthesizer may generate the second image coded data with a data amount different from a data amount of the first image coded data input to the image coded data analyzer.
This will offer an advantage of providing an image coded data re-encoding apparatus which can perform transformation between data of different amounts with reduced image degradation and processing delay.
The image coded data re-encoding apparatus may further comprise a coefficient deletion/addition/correction portion for deleting part of the transform coefficients or quantization indices, which are extracted by the image coded data analyzer, and for correcting the transform coefficients or quantization indices in accordance with a ratio of amounts of data to be transformed.
This will offer an advantage that the amount of data can be reduced because part of the transform coefficients or the quantization indices is deleted, and that the image quality of the decoded image can be improved as compared with a system which simply thins out the transform coefficients or quantization indices because the remainder of the transform coefficients or the quantization indices is corrected in accordance with the ratio of amounts of data to be transformed.
The image coded data re-encoding apparatus may further comprise a coefficient deletion/addition/correction portion for deleting part of the transform coefficients or quantization indices, which are extracted by the image coded data analyzer, and are weighted in accordance with relationships between the transform coefficients or quantization indices and their neighboring transform coeffic
Asai Kohtaro
Murakami Tokumichi
Nishikawa Hirofumi
Lee Young
Mitsubishi Denki & Kabushiki Kaisha
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