Television – Format conversion
Reexamination Certificate
1999-12-30
2002-12-31
Miller, John (Department: 2614)
Television
Format conversion
C348S443000, C348S445000, C348S715000, C348S725000
Reexamination Certificate
active
06501508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital receiver and more particularly to an apparatus for converting the size of an input image in compliance with an output format of a digital TV.
2. Discussion of Related Art
A digital TV receives images of various types and sizes. Thus, a digital TV requires a format converter which converts the type and size of images in compliance with the format of the display device. Particularly when the input video format is of a high definition grade but the display format is of a standard definition grade, a vertical and horizontal filtering is required. For example, when the input video format has 1,920 pixels×1,080 lines and the display format has 720 pixels×480 lines, the input video must be filtered in the vertical and horizontal directions.
FIG. 1
is a block diagram of a digital receiving system in the related art including a format converter. Referring to
FIG. 1
, a tuner
102
selects a channel from a plurality of channels received through an antenna
101
and outputs the selected channel to a demultiplexer
103
. The demultiplexer
103
selects a desired program from a plurality of programs included in the channel and divides the selected program into audio and video bit stream packets. The divided video bit stream is output to a video decoder
104
, which removes the overhead (header information, start code, etc.) from the video bit stream and variable-length-decodes the data information. The video decoder
104
also inverse quantizes, inverse discrete cosine transforms and using motion vectors for the decoded data information, motion compensates the data information to restore the pixel values of the original picture. The restored picture is then output to a format converter
105
. The format converter
105
converts the input video format to conform to the display format if the two formats are different, and outputs the received picture for display.
FIG. 2
is a block diagram of a format converter for performing video format conversion in the vertical direction. The input video data is received through an input buffer
201
and stored in the first line memory of a memory
202
. One line memory is capable of storing the amount of data corresponding to one line of input video data, and the number of line memories of memory
202
is equal to the number of taps in a filter
206
. The line memories of memory
202
have a first-in-first-out (FIFO) structure. Thus, when data is read, the previous data is output from a line memory and input to the next line memory. The vertical format conversion for the video data will be explained below.
One address of a line memory may store data by one byte or by eight bytes. If the data is stored by eight bytes, a P2S unit
203
is required to convert the eight-byte data into a byte unit which can be filtered by the filter
206
. Each P2S of P2S unit
203
is a kind of multiplexer that converts the data of eight bytes output in parallel from each line memory into data of one byte. The one-byte data which passed through the P2S unit
203
enters the filter
206
. The filter
206
multiplies the input video data items {I
0
, I
1
, . . . , In} by filter coefficients {C
0
, C
1
, . . . , Cn}, respectively, and adds the multiplied data items, as represented by Equation (1) below, where n is an odd number.
OUT=(
I
0
×
C
0
)+(
I
1
×
C
1
)+, . . . ,+(
I
center×
C
center)+, . . . ,+(
In×Cn
) (1)
The coefficients of the filter
206
are previously stored in a filter coefficient table
204
. Accordingly, the coefficients required for a current format conversion are selected under the control of a controller
200
, and are loaded on the filter
206
through a buffer
205
. For example, when the filter
205
has five taps, five line memories of memory
202
are required.
Referring to FIG.
3
A~
3
C, when the input video data items are vertically decimated by half, data items {D
2
, D
4
, D
6
, . . . } become the input center values (Icenter) of filter
206
. Also, the data items corresponding to lines D
0
~D
4
are stored sequentially from the lowest line memory due to the line shift of the input data, as shown in
FIG. 3B
, and are output to the filter
206
. The locations of the input center values (Icenter) and the coefficient center value (Ccenter) of filter
206
are fixed. Particularly, the coefficient center value and the input center values must be input respectively through the Ccenter and Icenter at all times. Moreover, the filter coefficients are symmetrical with respect to the Ccenter. Accordingly, the center value of input data item D
2
is input into Icenter of filter
206
to be multiplied by the coefficient center value C
2
.
Typically, the coefficient center value Ccenter is given
20
the largest value among the coefficient values input into the filter
206
.
FIG. 3B
shows an example in which the coefficient center value C
2
is 0.4, the coefficient values C
1
and C
3
on either sides of coefficient center value C
2
is 0.2, and the outermost coefficient values C
1
and C
4
is 0.1. Thus, the filter coefficient serves as a kind of weight and the output of the filter
206
becomes as follows.
OUT=
D
0
C
0
+
D
1
C
1
+
D
2
C
2
+
D
3
C
3
+
D
4
C
4
=0.1
D
0
+0.2
D
1
+0.4
D
2
+0.3
D
3
+0.1
D
4
.
As the data items corresponding to lines D
0
~D
4
are output to the filter
206
, the data items corresponding to lines D
2
~D
6
are stored sequentially from the lowest line memory of memory
202
, as shown in
FIG. 3C
, and are output to filter
206
. The center value of the input data item D
4
is input into Icenter of filter
206
to be multiplied by the coefficient center value C
2
(=0.4). Thus, the output of filter
206
becomes 0.1D
2
+0.2D
3
+0.4D
4
+0.2D
5
+0.1D
6
. According to the aforementioned process, the number of lines of the video data output from the input buffer
201
is reduced by half as they pass through the filter
206
.
A line memory
207
connected to the output port of the filter
206
is used when the output video data is extracted between lines of video, i.e. when interpolation is needed. For example, if 1080 lines are converted into 480 lines, the filter
206
first converts the 1080 lines into 540 lines through the ½ down-filtering. Thereafter, the 540 lines are converted into 480 lines by interpolation because 540 is not a multiple of 480. Thus, when interpolation is required, the filtered result of the first video line is stored in the line memory
207
until the filtered result of the second video line is output from the filter
206
. An interpolation unit
208
then interpolates the filtered result of the first line stored in line memory
207
and the filtered result of the second video line output by the filter
206
.
In other words, the video data that was filtered by the filter
206
is either stored in the line memory
207
according to the format conversion and be interpolated with the filtered result of the next video line data, or output without interpolation by bypassing the line memory
207
.
As shown in
FIG. 4
, for example, when the output data must be extracted from a position (
1
) between video data items D
3
and D
4
, i.e. the middle of the two lines D
3
and D
4
, the video data items D
1
~D
5
are first filtered by filter
206
and stored in the line memory
207
. The filtered result of the video data items D
1
~D
5
is represented by Equation (2) below.
OUT (
D
1
~
D
5
)=
D
1
C
0
+
D
2
C
1
+
D
3
C
2
+
D
4
C
3
+
D
5
C
4
(2)
Thereafter, the filter
206
filters video data items D
2
~D
6
and outputs the filtered result to the interpolation unit
207
. The filtered result of video data items D
2
~D
6
is represented by the Equation (3) below.
OUT (
D
2
~
D
6
)=
D
2
C
0
+
D
3
C
1
+
D
4
C
2
+
D
5
C
3
+
D
6
C
4
(3)
The interpolation
Ahn Jin Ho
Han Dong Il
Song Seung Chul
Birch & Stewart Kolasch & Birch, LLP
Desir Jean W.
LG Electronics Inc.
Miller John
LandOfFree
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