Television – Format conversion – Involving both line number and field rate conversion
Reexamination Certificate
1999-03-02
2002-09-03
Miller, John (Department: 2614)
Television
Format conversion
Involving both line number and field rate conversion
C348S454000, C348S459000
Reexamination Certificate
active
06445419
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus, more specifically, to an image processing apparatus for producing display image data of the Phase Alternating by Line (PAL) system from a coded image signal of the National Television System Committee (NTSC) system compressed by using the system of Moving Picture Experts Group (MPEG).
2. Description of the Related Art
In the image signal specified by either the NTSC system or PAL system, the frame rate is different in the both cases: NTSC system has 30 frames/sec. or strictly 29.97 frames/sec., while PAL system has 25 frames/sec. For this reason, a frame rate transformation is required in the case of displaying the image signal of PAL system in response to the image signal coded by NTSC system.
FIG. 5
is an electrical block diagram showing an MPEG-decoded image processing apparatus having a transformation function of frame rate to be transformed from the NTSC system to PAL system, for explaining a related art.
FIG. 6
is a flow chart explaining an operation of the image processing apparatus in the decoding.
FIG. 7
is a flow chart explaining an operation of the image processing apparatus in the display. FIGS.
8
(
a
),
8
(
b
) and
8
(
c
) are explanatory diagrams for explaining the frame rate transformation by the image processing apparatus.
As shown in
FIG. 5
, the MPEG-decode image processing apparatus having the transformation function of frame rate to be transformed the NTSC system to PAL system, constitutes substantially an input buffer
101
, a variable length decoder
102
, a reverse quantizing part
103
, a reverse discrete cosine transformation (DCT) part
104
, a motion compensating part
105
, an image memory
116
having a first core-picture memory
106
, a second core-picture memory
107
, a B-picture memory
108
and a switching part
109
. The apparatus also includes an aspect ratio transforming filter
110
, a PAL synchronizing signal generator
111
, a decoding controller
112
, a skipped image deciding part
113
, a memory controller
114
and a display controller
115
.
According to such constitution, the input buffer
101
stores temporarily a coded image input signal supplied from a coded image signal supply end. The variable length decoder
102
decodes the coded image input signal having variable length codes. The reverse quantizing part
103
quantizes reversely the decoded signal that has been quantized at the coded signal supply end. The reverse DCT part
104
reversely transforms the decoded signal that has also been transformed as discrete cosine transformation (DCT) at the coded signal supply end. The motion compensating part
105
adds the decoded image signal to an image reference signal in correspondence with a process such that an image signal is coded by a difference from the image reference signal at the coded signal supply end. The first core-picture memory
106
and second core-picture memory
107
each receives a core picture (I-picture or P-picture) alternately and outputs it therefrom. The B-picture memory
108
holds a B-picture itself. The switching part
109
selects either one of the core picture from the first and second core-picture memories
106
and
107
or the B-picture from the B-picture memory
108
, and outputs the one of those. As is apparent from the constitution, the image memory
116
has the first and second core-picture memories
106
and
107
, the B-picture memory
108
, and the switching part
109
.
The aspect ratio transforming filter
110
transforms an aspect ratio of an output image data from the image memory
116
. The PAL synchronizing signal generator
111
generates a synchronizing signal for controlling a timing between the decoding operation and display operation in PAL system. The decoding controller
112
controls the decoding operation to be performed in the necessary components in response to the synchronizing signal of the PAL system output from the PAL synchronizing signal generator
111
. The skipped image deciding part
113
decides a frame to be skipped and instructs so as to control the frame to the decoding controller
112
for a purpose of transformation between the NYSC and PAL system.
The memory controller
114
controls the image data being stored in the image memory
116
in response to an instruction from the decoding controller
112
, and also controls to read the image data from the image memory
116
in response to an instruction from the display controller
115
. The display controller
115
controls the read operation of the image memory
116
controlled by the memory controller
114
in response to the synchronizing signal from the PAL synchronizing signal generator
111
, and also controls the operation of the aspect ratio transformation performed in the aspect ratio transforming filter
110
.
Referring to
FIGS. 5
to
8
, the operation of frame rate transformation from the NTSC system to PAL system will be described below as a related art. First, an image transmission manner specified by MPEG system in general will be explained. In the case of MPEG system, the image transmission is carried out by using three types of image data containing an I-coded data, P-coded data and B-coded data at every predetermined number of frames dependent on original image data. Specifically, the I-coded data is image data coded at one frame and completed within one image data. The decoded I-coded data is referred to as an I-picture. The P-coded data is image data coded by a difference extracted from a reference of image data which is previously generated from either the I-coded data or P-coded data. The image data decoded by adding the difference data obtained from decoding the P-coded data to the reference image data, is referred to as a P-picture. The B-coded data is image data coded by a difference extracted from a reference of image data that is generated from either the immediately preceding and succeeding I-coded data or the P-coded data. The image data decoded by adding a difference data obtained from decoding the B-coded data to the reference image is referred to as a B-picture.
The image processing apparatus shown in
FIG. 5
transforms the frame rate from NTSC system to PAL system with the B-picture skipped and displayed in the ratio of one field to six frames when a coded image input signal is decoded in PAL system.
Referring to
FIGS. 5 and 6
, the decoding operation by the image processing apparatus will be described below. The decoding operation is first carried out by the decoding controller
112
controlling the necessary components in response to the synchronizing signal of PAL system output from the PAL synchronizing signal generator
111
.
That is, the coded image input signal containing variable length codes of the NTSC system is held in the input buffer
101
, thereafter, it is decoded in the variable length decoder
102
. At this time, a frame to be skipped is decided by the skipped image deciding part
113
, and the skip of B-picture is carried out at the time of the decoding performed in the variable length decoder
102
with the decoding controller
112
controlled. The variable length decoded signal is reversely quantized in the reverse quantizing part
103
, and transformed as a reverse discrete cosine transformation by the reverse DCT part
104
. Afterward, either the I-picture or P-picture output from the motion compensating part
105
is alternately written into the first and second core-picture memories
106
and
107
and the B-picture is written into the B-picture memory
108
, in response to the control by the memory controller
114
, terminating the decoding of one frame.
The subsequent operation will be explained with a flow chart shown in
FIG. 6. A
decode-starting position on the frame specified by PAL system is detected at the time of termination of decoding a previous frame in step Q
1
. Afterward, if five frames or more are decoded in step Q
2
, the decoded image signal is confirmed as a B-picture in step Q
3
and one frame is skipped in
Miller John
Scully Scott Murphy & Presser
Shang Annan Q
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