Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
2000-09-18
2003-12-02
Britton, Howard (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C375S240160, C375S240280
Reexamination Certificate
active
06658058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a picture coding apparatus composing a terminal apparatus in which data including picture data is transmitted and received.
2. Description of Related Art
An example of a conventional picture coding apparatus using a H.263 coding method (ITU-T Recommendation) is shown in FIG.
1
.
In a motion compensation predicting unit
27
, referential picture data of a memory unit
19
and input picture data are received, a block matching operation is performed for each macro-block (16 pixels×16 lines), and motion information is obtained. Thereafter, in the motion compensation predicting unit
27
, referential picture data of a position corresponding to the motion information is received from the memory unit
19
, and a predicted picture is produced. The predicted picture produced in the motion compensation predicting unit
27
is output to a subtracting unit
13
and a locally-decoded picture producing unit
18
.
In the subtracting unit
13
, a differential picture obtained from the input picture data and the predicted picture is produced for each macro-block.
Thereafter, in a coding mode judging unit
14
, a coding mode (intra/inter) is selected according to a prescribed method for each macro-block. In cases where an intra-coding mode is selected, picture data of one macro-block is output to a discrete cosine transforming (DCT) unit
15
. In contrast, in cases where an inter-coding mode is selected, the differential picture of one macro-block is output to the DCT unit
15
. The selected coding mode is output to the locally-decoded picture producing unit
18
.
In the DCT unit
15
, the differential picture input of the macro-block is divided into a plurality of differential pictures respectively corresponding to one block (8 pixels×8 lines), and a DCT processing is performed for the differential picture for each block of the macro-block. The differential pictures, for which the DCT processing is performed, are output to a quantizing unit
16
.
In the quantizing unit
16
, a quantization processing is performed for each differential picture according to a prescribed method, quantized DCT coefficients (hereinafter, expressed by a group of quantization indexes) are output to a variable length coding (VLC) unit
20
and a locally-decoding prediction error signal producing unit
17
.
In the locally-decoding prediction error signal producing unit
17
, an inverse quantization processing and an inverse DCT processing are performed for the group of input quantization indexes, and a locally-decoding prediction error signal is produced. The produced locally-decoding prediction error signal is output to the locally-decoded picture producing unit
18
.
The locally-decoded picture producing unit
18
is operated according to the coding mode for each macro-block. In cases where the coding mode is the intra-coding mode, the input locally-decoding prediction error signal is written in the memory
19
as a locally-decoded picture. In contrast, in cases where the coding mode is the inter-coding mode, the locally-decoding prediction error signal and the predicted picture are added to each other to produce a locally-decoded picture, and the locally-decoded picture is written in the memory
19
.
In the VLC unit
20
, header information and the group of quantization indexes are coded according to the H.263 syntax, and a multiplexed bit stream is output.
In the above header information, a synchronization signal is included for each prescribed interval corresponding to a prescribed number of blocks, and a differential motion vector (which denotes the difference between a motion vector of a corresponding macro-block and a motion vector of a macro-block adjacently placed on the left side of the corresponding macro-block) is included for each macro-block.
FIG. 2
shows an example of the bit stream output from the VLC unit
20
. In this example, header information including one motion vector is added to the bit stream for each group of quantization indexes corresponding to one macro-block, and one synchronization signal is inserted into the header information every eight macro-blocks. That is, one synchronization signal is inserted into the bit stream every eight pieces of header information.
However, as is described above, in the conventional picture coding apparatus, a picture coding processing is performed regardless of quality conditions of a data transmission line through which media data including compressed picture data is transmitted. Therefore, in cases where the quality conditions of the data transmission line become worse because of some causes, it becomes impossible to play back any type of media data on the receiving side. As a result, there is a problem that the media data playback fails when the media data decoded result is displayed.
SUMMARY OF THE INVENTION
Therefore, to make the playback of any type of media data possible on the receiving side regardless of the quality conditions of the data transmission line, an object of the present invention is to provide a picture coding apparatus in which compressed picture data is output while performing the control of an amount of bits of the compressed picture data, the control of insertion intervals of synchronization signals and the control relating to insertion intervals of intra-coded blocks.
To achieve the above object in a present invention, a picture coding apparatus composing a terminal apparatus, in which data including picture data is transmitted and received, is characterized in that the picture coding apparatus comprises differential motion information threshold value determining means for setting a threshold value, which gives a value range to differential motion information, according to a quality condition of a given line, and outputting the threshold value; and
picture data coding means for performing a motion compensation processing for input picture data and reproduced picture data obtained by performing a coding processing and a decoding processing for preceding picture data precedent to the input picture data to obtain motion information, calculating a difference between the motion information and preceding motion information obtained in a preceding motion compensation processing precedent to the motion compensation processing as the differential motion information, producing a renewed differential motion information by setting a limit to the differential motion information according to the threshold value set by the differential motion information threshold value determining means in cases where the differential motion information is beyond the value range given by the threshold value, coding the input picture data and outputting compressed picture data.
Also, to achieve the above object in a next present invention, a picture coding apparatus composing a terminal apparatus, in which data including picture data is transmitted and received, is characterized in that the picture coding apparatus comprises control signal setting means for outputting a control signal indicating a first mode, at which the picture data quantized in a frequency area is coded, or a second mode, at which the picture data quantized in a frequency area is not coded, according to a quality condition of a given line; and
picture data coding means for coding the input picture data and header information in cases where the control signal output from the control signal setting means indicates the first mode, coding only the header information in cases where the control signal indicates the second mode, and outputting compressed picture data.
Also, to achieve the above object in a next present invention, a picture coding apparatus composing a terminal apparatus, in which data including picture data is transmitted and received, is characterized in that the picture coding apparatus comprises code-word limiting means for setting a threshold value, which gives a value range of a code length to a variable length code-word obtained in an entropy coding of picture data for which an
Asai Kohtaro
Hasegawa Yuri
Kuroda Shin-ichi
Murakami Tokumichi
Ogawa Fuminobu
Britton Howard
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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