Television – Bandwidth reduction system – Frame field or line dropping followed by time expansion and...
Reexamination Certificate
1996-08-01
2002-03-12
Faile, Andrew (Department: 2611)
Television
Bandwidth reduction system
Frame field or line dropping followed by time expansion and...
C348S440100, C348S466000, C382S251000, C725S143000
Reexamination Certificate
active
06356309
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video coding device, and more particularly to a device for coding and transmitting moving pictures.
2. Description of the Background Art
(First Conventional Example)
Conventional video compression coding systems for moving picture communication at a low bit rate include ITU Recommendation H.261.
FIG. 18
is a block diagram showing the structure of a video coding device for realizing the video coding system recommended in H.261. Structures and operations of parts of this first conventional example will be described below.
In
FIG. 18
, a video coding device
90
includes a video input portion
11
, a coding device
12
, a transmission control device
17
and an output device
18
. The transmission control device
17
includes a transmission buffer
171
and a transmission control portion
172
.
The video input portion
11
, composed of a camera etc., performs input of video. The coding device
12
codes the video inputted from the video input portion
11
according to the video coding method recommended in H.261. The transmission buffer
171
stores the video data coded in the coding device
12
. The transmission control portion
172
transmits the coded video data stored in the transmission buffer
171
to a video receiving device
1000
at a predetermined transmission rate through the output device
18
.
FIG. 19
is a block diagram showing more detailed structure of the coding device
12
in FIG.
18
. In
FIG. 19
, the coding device
12
includes a video input device
100
, a coding control portion
101
, a SW (switch)
102
, a scan conversion portion
103
, a differential portion
104
, a quantization portion
105
, a motion vector detecting portion
106
, a motion compensation portion
107
, a frame memory
108
, a inverse quantization portion
109
, an addition portion
10
a
, a multiplexer
10
b
and a code output device
10
c.
The SW
102
switches whether to code or not a video frame inputted from the video input portion
11
(that is, frame dropping or not). The coding control portion
101
carries out frame dropping control for controlling whether the video frame inputted at the video input portion
11
is to be coded and transmitted, or to be dropped without coded and quantization control for determining the most suitable quantization step size from both the reproducibility of the motion and the video quality. The scan conversion portion
103
scan-converts the moving picture data inputted from the video input device
100
and outputs it as data in block unit composed of a plurality of pixels. The motion vector detecting portion
106
detects the motion vector of the data block outputted from the scan conversion portion
103
. The frame memory
108
stores local decoded moving picture data one frame before. The motion compensation portion
107
retrieves a prediction value from the moving picture data in the frame memory
108
on the basis of the motion vector information which is an output of the motion vector detecting portion
106
and outputs the same.
The differential portion
104
calculates the difference between the data block from the scan conversion portion
103
and the prediction value from the motion compensation portion
107
to output a prediction error. The quantization portion
105
quantizes the prediction error from the differential portion
104
. The inverse quantization portion
109
inversely quantizes the prediction error quantized in the quantization portion
105
. The addition portion
10
a
adds the prediction error inversely quantized in the inverse quantization portion
109
and the prediction value from the motion compensation portion
107
to calculate decode moving picture data and stores it in the frame memory
108
. The multiplexer
10
b
multiplexes the prediction error quantized in the quantization portion
105
and the motion vector detected in the motion vector detecting portion
106
.
Coding operation of the conventional video coding device constructed as described above will now be described. The frame dropping control and the quantization control by the coding control portion
101
will be described later.
The moving picture frame inputted from the video input portion
11
is inputted to the coding,device
12
. In the coding device
12
, the moving picture signal inputted from the video input device
100
is scan-converted by the scan conversion portion
103
and then inputted to the motion vector detecting portion
106
for each block formed of a plurality of pixels. The motion vector detecting portion
106
compares the local decoded video data one frame before stored in the frame memory
108
and the block inputted from the scan conversion portion
103
to obtain motion vector and outputs it to the motion compensation portion
107
and the multiplexer
10
b
. The motion compensation portion
107
finds a corresponding prediction value from the video data in the frame memory
108
on the basis of the inputted motion vector information and outputs it to the differential portion
104
and the addition portion
10
a.
The differential portion
104
calculates a difference between the block outputted from the scan conversion portion
103
and the prediction value outputted from the motion compensation portion
107
to find a prediction error and outputs it to the quantization portion
105
. The quantization portion
105
quantizes this prediction error with a quantization step size determined in the coding control portion
101
and outputs it to the multiplexer
10
b
and the inverse quantization portion
109
. The inverse quantization portion
109
inversely quantizes the prediction error and outputs it to the addition portion
10
a
. The addition portion
10
a
adds the inversely quantized prediction error and the prediction value outputted from the motion compensation portion
107
to decode the video data and stores it in the frame memory
108
. The quantized prediction error and the motion vector are multiplexed in the multiplexer
10
b
and stored in the transmission buffer
171
through the code output device
10
c
. The transmission control portion
172
transmits the coded video data in the transmission buffer
171
at a predetermined transmission rate to the video receiving device
1000
through the output device
18
.
Next, the frame dropping control performed in the coding control portion
101
will be described. Conventionally, as the frame dropping control system, the system of determining whether frame dropping is required or not on the basis of comparison between the accumulated amount in the transmission buffer and a determination threshold is proposed. (Refer to Yasuhiro Takishima et al. “A Study on Control Method for Low Bit Rate Video Coding,” The Institute of Electronics, Information and Communication Engineers, Spring National Meeting, D-311, pp.7-63, 1990.) The coding control portion
101
performs frame dropping control using the technique disclosed in this paper.
FIG. 20
is a sequence diagram showing operation of the conventional frame dropping control system. Referring to
FIG. 20
, the coding control portion
101
carries out coding of video frame if the accumulated amount in the transmission buffer
171
is smaller than a certain threshold at the start of coding (that is, it connects the devices
1
-
2
of the SW
102
) and if it is larger than the certain threshold, it does not code that video frame, but drops the frame. (That is to say, it connects the devices
1
-
3
of the SW
102
.) In
FIG. 20
, at the points (T
1
, T
3
) at which coding of the frame
2
and the frame
4
is started, the accumulated amount in the transmission buffer
171
exceeds the threshold, so that the frames
2
and
4
are dropped.
Next, the quantization control made in the coding control portion
101
will be described. Conventionally, the coding control system of determining a quantization step size for a coded frame using a coding rate of already coded video frames is proposed. (Refer to Japanese Patent Laying-Open No.7-107482.)
Kurobe Akio
Masaki Shoichi
Shinoda Mayumi
Faile Andrew
Matsushita Electric - Industrial Co., Ltd.
Srivastava Vivek
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Video coding device and video transmission system using the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Video coding device and video transmission system using the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Video coding device and video transmission system using the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2865617