JPH0385081A - Synchronizing picture transmitter - Google Patents

Abstract

PURPOSE:To build up a system immune to a transmission failt and to minimize the picture quality deterrioration by recovering a latter half of a just preceding data block when an error takes place in a synchronizing data. CONSTITUTION:When a communication fault takes place between a sender side equipment 1 and a receiver side equipment 2 and an error exists in a synchronizing data, a synchronization detection circuit 6 detects it and notifies it to a CPU 5. The sends a control signal to a data error recovery circuit 7 to recover the error in a picture data. Before the error in the synchronization data is detected, the data of the latter half of the data block stored finally in a V-RAM 4 is aborted. Then the data of the latter half of one preceding data block is copied therein. Then the all picture data of the data block whose latter half is recovered are used as the picture data of the data block having the synchronizing data error.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to repairing data transmission errors during reception in a synchronous image transmission device such as a video telephone.

In direct synchronous image transmission devices, especially devices that transmit still images,
One to several lines are transmitted as one data block, or one line divided into several parts is transmitted as one data block.

A synchronization signal (header), which is a predetermined data ψ arrangement, is added to the beginning of each data block to synchronize communication.

If a transmission error occurs due to a failure in the communication path, etc., and the synchronized data cannot be received, the missing synchronized data is detected by some means, and the image data of the data block following the synchronized data is Repair based on the data blocks before and after it. For example, in the case of a device that transmits one line in one data block, data from the previous line is copied to the line of the data block in which the error has occurred, and the data is used as data for that line.

When a transmission failure occurs on a normal communication path, the failure often continues for a certain amount of time. Therefore, when an error occurs in the synchronized data of a certain data block, there is a high probability that an error also occurs in the image data in the latter half of the data block immediately before it. In the conventional transmission device described above, only the data block in which an error has occurred is repaired, so the error in the previous data block is directly transferred to the current data block, and in the end, accurate repair is not performed. The image quality of the receiving screen was degraded.

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems and provide an image transmission device that restores image data as accurately as possible when a communication failure occurs.

In order to achieve the above-mentioned object, the present invention provides a synchronous image transmission device that transmits data blocks each consisting of synchronous data and image data, and detects that the synchronous data is abnormal upon reception. a synchronized data abnormality detection means for detecting an abnormality in the synchronized data; and when an abnormality is detected in the synchronized data, the image data in the latter half of the data block immediately before the data block is repaired, and the image data of the data block in which the abnormality has occurred in the synchronized data is restored. It is characterized by comprising an image data restoration means that generates image data based on image data of data blocks received before and/or after that.

If the synchronous data abnormality detection means detects an abnormality (error) in the synchronous data of the received data block, the image data restoration means first detects the data block received immediately before the data block in which the synchronous data abnormality occurred. Repairs the second half of the data block.

This is because if an abnormality occurs in the synchronized data, there is a high possibility that the immediately preceding data also has an abnormality. Next, image data of the data block in which an abnormality has occurred in the synchronization data is created based on the image data of the data blocks before and after it. For this purpose, various conventional error repair methods can be used.

The configuration of an image transmission device embodying the present invention will be described with reference to FIG. The transmission devices 1 and 2 of this embodiment are controlled by the CPU 5, and when operating as a receiving side, the first
As shown in the figure, there is a switch 3 that changes the destination of received data, a video memory (V-RA) that stores image data, and
M) 4. Consists of a synchronization detection circuit 6 that detects synchronization data in received data, a data error recovery circuit 7, and the like. In this embodiment, it is assumed that one data block is composed of synchronization data (SYNC) placed at the beginning and image data (PD) for one line of the screen.

The operation of the transmission device 2 on the receiving side will be explained with reference to the flowchart in FIG. (step #
1). When the synchronization detection circuit 6 detects correct synchronization data in the received data (step #2), the CPU 5 sends a control signal to the changeover switch 3, and transfers the received data to the V-RA.
Switch 3 is switched so that the signal is sent to M4 (step #3). In this way, the image data in the received data is stored in the V-RAM 4. Data of a predetermined length corresponding to the length of image data in l data block
- After storing in the RAM 4 (step #4), the CPU 5 switches the switch 3 again to the synchronization detection circuit 6 (step #1), and detects the synchronization data of the next data block. This is usually repeated for one screen (step #5).

If some communication failure occurs between the sending device 1 and the receiving device 2 and an error occurs in the synchronized data (for example,
If the synchronization data is not detected for a predetermined period of time or more), the synchronization detection circuit 6 detects that the synchronization data is not normal (step #2) and notifies the CPU 5 to that effect. At this time, the CPU 5 sends a control signal to the data error repair circuit 7 to cause it to repair the error in the image data (step #6
). This error recovery method will be explained with reference to FIG.

First, the data PD-D in the latter half of the data block DB (N-1) that was last stored in the V-RAM 4 before the error in the synchronization data (SYNC) was detected is discarded.

Next, the second half data PD-B of the previous data block DB (N-2) is copied there. Then, the data block DB (N-
Let all the image data PD-C+PD-B of 1) be the image data of the data block DB(N) in which the synchronous data error has occurred.

In this way, in the transmission device of this embodiment, when an error is detected in the synchronous data, there is a high possibility that an error has also occurred in the latter half of the immediately preceding data block. It not only repairs the data block that was previously deleted, but also the second half of the data block immediately before it. Therefore, even if a transmission failure occurs, deterioration in image quality can be minimized.

As explained above, in the present invention, when an error occurs in synchronized data, the second half of the immediately preceding data block, which is also likely to have an error, is also repaired, so image quality deterioration is minimized. This makes it possible to construct a system that is robust against transmission failures.

[Brief explanation of drawings]

Fig. 1 is a block diagram mainly showing the configuration of the receiving device side of a synchronous image transmission device embodying the present invention, Fig. 2 is a flowchart of the processing performed by the receiving device, and Fig. 3 is a diagram showing the case when synchronous data is abnormal. FIG. 3 is an explanatory diagram showing how image data is restored. DB(N-2), DB(N-1), DB(N)...
・Data block 5YNC...Synchronized data PD-A, PD-B, PD-C, PD-D...
・Image data applicant Shizuo Sano, Sharp Corporation Figure 1 Figure 2

Claims (1)

[Claims] (1) In a synchronous image transmission device that transmits data blocks each consisting of synchronous data and image data, a synchronous data abnormality detection means detects whether or not the synchronous data is abnormal at the time of reception; When an abnormality is detected in the data, the image data in the second half of the data block immediately before that data block is repaired, and the image data of the data block in which the abnormality occurred in the synchronized data is received before and/or after that. 1. A synchronous image transmission device comprising: image data restoration means for generating image data based on image data of a data block.