Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-10-30
2002-05-07
Vincent, David R. (Department: 2732)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S537000
Reexamination Certificate
active
06385212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data switching apparatus used in transmission or broadcasting apparatuses for selecting and transmitting the data from a plurality of received data without changing coding unit.
2. Description of the Prior Art
FIG. 16
shows a conventional data switching apparatus provided in a TV studio for example. In
FIG. 16
, received data
110
A and
110
B are TV signals (NTSC signals and so on) input to the present apparatus. The received data
110
A and
110
B include information such as a vertical drive pulse which shows a frame (synchronization). The conventional data switching apparatus also include frame detectors
101
A,
101
B, and switches
102
A,
102
B. The switches
102
A and
102
B respectively turn ON/OFF the received data
110
A and
110
B at the timing from the frame detectors
101
A and
101
B under the control of a control unit
103
. The control unit
103
controls either of switches
102
A and
102
B to turn ON/OFF by an external switching request (not shown).
The operation is explained below. A plurality of received data
110
A and
110
B input into the present apparatus are TV signals including synchronization signals. The timing of the synchronization signals is controlled so that respective timings of the received data
110
A and
110
B are the same.
The frame detectors
101
A and
101
B detect frames (synchronization signal) such as a vertical driving pulse of the received data and provides them to the switches
102
A and
102
B. This frame represents the head of the data defining the TV image. The control unit
103
instructs either of the switches
102
A and
102
B to be ON and the other to be OFF.
The switches
102
A and
102
B are switched by the instruction of the control unit
103
according to the frame timing of the frame detectors
101
A and
101
B. Since the frames of a plurality of received data
110
A and
110
B are all synchronized, the timing provided from the frame detectors
101
A and
101
B to the switches
102
A and
102
B are all synchronized. Therefore, the respective switches
102
A and
102
B are switched at the same time. At this time, only one switch turns ON and the other turns OFF.
In this way, the present apparatus always selects one data stream from a plurality of received data. In
FIG. 16
, only two pairs of frame detector
101
A and switch
102
A, and frame detector
101
B and switch
102
B are shown for simplicity of explanation. But, the data switching apparatus of
FIG. 16
may have plural pairs of the frame detectors and switches. Since the switches
102
A and
102
B are switched at the head of the frame upon selecting the data, the frame of the data at the vicinity of switching point can be held in a constant period.
Therefore, the data switched by this apparatus does not have bad influence to the image due to switching such as a image turbulence (noise) and a step-out of the frame synchronization, and therefore, the image can be kept in the same as a state without switching the data.
As explained above, the conventional switching apparatus has been necessary to meet frames of all data for each frame according to an externally applied clock. Accordingly, there is a problem in that the conventional switching apparatus cannot process the data whose respective frame timings are not synchronized.
Moreover, since the frame periods of all received data must be the same, the conventional apparatus cannot process the data if the received data is encoded with a variable length code.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a data switching apparatus which links any data at any point when it switches data.
It is another object of the present invention to provide a data switching apparatus which links the data without breaking the data.
It is a further object of the present invention to provide a data switching apparatus which operates normally even if the data unit detector delays in detecting the data unit.
It is a still further object of the present invention to provide a data switching apparatus which discards the undesired data by replacing undesired data with invalid data.
It is a further object of the present invention to provide a data switching apparatus which decreases the video buffer remaining quantity in the decoder to prevent the buffer from overflowing.
It is a further object of the present invention to provide a data switching apparatus which increases the video buffer remaining quantity in the decoder to prevent the buffer from underflowing.
It is a further object of the present invention to provide a data switching apparatus which holds the video buffer remaining quantity in the decoder to prevent the buffer from overflowing and underflowing.
It is a further object of the present invention to provide a data switching apparatus which increases the switching points for switching the data normally.
According to one aspect of the invention, a data switching apparatus includes plural data unit detectors each for detecting a coding unit of a data from a received data; plural data storages each for storing a received data in a buffer and transmitting the received data at a given time from a point specified by the data unit detector; and a data selecting unit for selecting and transmitting only one data stream from a plurality of data streams which are transmitted respectively from the plural data storages.
According to another aspect of the invention, in the data switching apparatus, the data storage starts and terminates the data transmission at the end of the coding unit in the data detected by the data unit detector; and the data selecting unit switches the data streams from the data storage so that each of the data stream from respective data storage is linked together in a continuous data stream.
According to other aspect of the invention, in the data switching apparatus, each respective storage include a delay unit which delays the received data for more than a predetermined time.
According to further aspect of the invention, the data switching apparatus further includes a pattern generator for transmitting a predetermined data pattern to the data selecting unit upon request from the data selecting unit.
According to further aspect of the invention, in the data switching apparatus, the pattern generator generates and transmits invalid data, that is, data quantity requested by the data selecting unit.
According to further aspect of the invention, in the data switching apparatus, the pattern generator generates and transmits data quantity requested by the data selecting unit and stuff data for video data.
According to further aspect of the invention, in the data switching apparatus, the pattern generator generates and transmits data quantity requested by the data selecting unit and unit coding video data with small information quantity.
According to further aspect of the invention, the data switching apparatus further includes a comparator for comparing each value of respective decoding start delay time included in two received data to be switched, wherein the data selecting unit inserts stuff data in the video data when the decoding start delay time before switching is larger than that after switching, and inserts unit coding video data with a small information quantity in the video data when the decoding start delay time before switching is smaller than that after switching, so that the respective decoding start delay times included in the two received data to be switched become the same.
According to further aspect of the invention, a data switching apparatus includes plural data unit detectors each for detecting a coding unit of received data; plural data storages each for storing a received data in a buffer and transmitting the received data specified from the data unit detector at a given time from a point specified by the data unit detector; and a multiplexer for multiplexing and transmitting any numbers of data streams from a plurality of data streams which are transmitted respectively from t
Baba Masayuki
Kato Yoshiaki
Murakami Tokumichi
Mitsubishi Denki & Kabushiki Kaisha
Vincent David R.
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