JPS62266990A - Inter-frame decoder - Google Patents

Abstract

PURPOSE:To prevent a random picture from being projected on a receiving picture monitor by outputting the signal of a memory circuit by a selection circuit when a decoder between frames does not receive an encoding signal between the frames. CONSTITUTION:Encoding data between the frames is inputted to an input terminal 1, decoded into a TDM signal in a decoding circuit 4 between the frames and a decoding TDM signal (c), a frame pulse (d) indicating the top of the frame and a signal (d) indicating that the decoding error is not present are outputted. The signal (c) is ordinarily outputted to an output terminal 3 through the selection circuit 7. An FF5 is ordinarily reset and when it is reset by a control signal (e) from an input terminal 2, a timing is taken by the pulse (d) in a register 6 to have the selection signal of the circuit 7 and the circuit 7 selects the signal from the memory circuit 8. At this time, in the circuit 8, since the signal of its own is fed back, the data is not updated but the decoding TDM signal before a signal (g) is changed over is repeatedly outputted and a still picture is projected on the receiving picture monitor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an interframe decoding device for decoding an interframe coded television signal.

[Conventional technology]

In a system such as a video conference, a signal such as a facsimile is passed through a wideband PCM transmission line (PCM - next group level) that transmits a signal compressed and encoded using interframe coding technology, and one transmission is performed. There are cases where it is desired to share the line and use the line efficiently. If you use the line in this way, from the perspective of the interframe decoding device, the line will be disconnected for several seconds while transmitting facsimile signals, making it impossible to receive encoded signals, and causing random images to appear on the receiving monitor. The problem arises that the image is photographed.

[Problem that the invention seeks to solve]

The object of the present invention is that when the line is used as described above, the line is blocked for transmitting other signals, and while the line for transmitting video is disconnected, the line is disconnected. To provide an interframe decoding device which continues to reproduce the previous decoded image and prevents random images from being displayed on a received image monitor.

[Means for solving problems]

An uninvented interframe decoding device includes an interframe decoding circuit capable of detecting decoding errors, a storage circuit capable of storing one frame of decoded TDM signals of the interframe decoding circuit, and an interframe decoding circuit capable of storing one frame of decoded TDM signals of the interframe decoding circuit. When a control signal indicating that encoded data is not input is received from the outside, the first state is entered, and when no decoding error is detected in the interframe decoding circuit, the flip-I flow enters the second state. receives a decoded signal from the interframe decoding circuit and a signal from the storage circuit, selects a signal from the storage circuit when the flip-flop is in a first state, and selects a signal from the storage circuit when the flip-flop is in a second state. The apparatus further includes a selection circuit that selects a decoded signal from the interframe decoding circuit and outputs the decoded signal to the storage circuit and the outside.

When the interframe decoding device does not receive an interframe encoded signal, the selection circuit selects the signal of the storage circuit, and therefore updating of the signal of the storage circuit is prohibited. That is, the decoded image before the line was disconnected continues to be reproduced, and no random image is displayed on the received image monitor.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of an interframe decoding device of the present invention. Interframe encoded data is input to the input terminal 1, decoded into a TDM signal by the interframe decoding circuit 4, and a decoded TDM signal C, a frame pulse d indicating the beginning of the frame, and a signal indicating that there is no decoding error are output. Ru. The decoded TDM signal C is normally output to the output terminal 3 via the selection circuit 7. Further, the output signal is stored for one frame time in the storage circuit 8 and outputted to the selection circuit 7. The flip-flop 5 is set by a control signal e from the input terminal 2, and is reset if there is no error as a result of decoding error detection.

The flip-flop 5 is normally reset, but when it is set to a set state by the control signal e, it is timed by the frame pulse d in the register 6 and becomes the selection signal g of the selection circuit 7, which receives the signal from the storage circuit 8. You will be able to choose. At this time, since the memory circuit 8 is fed back with its own signal, the data in the memory circuit 8 is no longer updated, and the decoded TDM signal before the selection signal g is switched is repeatedly output to the output terminal 3. In other words, a still image will be displayed on the reception image monitor. The flip-flop 5 remains in the set state until the control signal e is turned off and no decoding error occurs in the interframe decoding circuit 4, and enters the reset state only after the No. 12 error disappears. Therefore, the output terminal 3 receives no errors. A signal that does not exist will be output. In addition, input terminal 2
The control signal e is a signal indicating that the transmission path is occupied by other signals (for example, facsimile data) instead of interframe encoded data, and the input terminal 1 is not receiving interframe encoded data. Further, decoding errors in the interframe decoding circuit 4 can be detected by, for example, calculating and comparing the respective parities of the local decoded signal of the interframe decoding circuit and the decoded signal of the interframe decoding circuit 4. .

〔Effect of the invention〕

As explained above, the present invention provides a storage circuit and a selection circuit, and further inputs a control signal indicating that interframe encoded data is not received to an input terminal of an interframe decoding device, and this control signal is input to an input terminal of an interframe decoding device. When this happens, the selection circuit outputs the signal from the storage circuit, thereby having the effect of prohibiting the output of an abnormal signal to the receiving image monitor (maintaining the screen before the abnormality).

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of an interframe decoding device of the present invention. 1.2...Input terminal. 3... Output terminal, 4... Inter-frame decoding circuit, 5... Flip-flop, 6... Register, 7... Selection circuit, 8... Memory circuit. Figure 1

Claims (1)

[Claims] An interframe decoding device that decodes an interframe encoded television signal, comprising an interframe decoding circuit that can detect decoding errors, and a decoded TDM signal of the interframe decoding circuit for one frame. When the interframe decoding circuit receives a control signal from the outside indicating that interframe encoded data is not input, the interframe decoding circuit enters a first state, and the interframe decoding circuit detects a decoding error. a flip-flop that is in a second state when the interframe decoding circuit is not in the first state; an interframe decoding device comprising a selection circuit that selects a decoded signal from the interframe decoding circuit when the flip-flop is in a second state, and outputs the decoded signal to the storage circuit and the outside.