JPH044798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a moving image transmission device, and particularly relates to frame drop control in the device.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional moving image transmission device. In the figure, 1 is a camera, 2 is digital image input data, 3 is an input double buffer, and 4 is a block diagram showing a conventional moving image transmission device.
is a transmission double buffer, 5 is a variable length encoder, and 6 is a variable length encoder.
is a receiving double buffer, 7 is a variable length decoder, 8
is an output double buffer, 9 is a monitor, 10 is image output data, 11 is a transmission path, 12 is a camera synchronization signal, 13 is a transmission double buffer switching signal, 14 is a monitor synchronization signal, and the above 3 to 5 are for the image transmitter 20. 6 to 8 are provided in the image receiver 21.

On the other hand, FIG. 4 is a timing chart for explaining the operation of the conventional device. In the figure, W indicates writing to the buffer, R indicates reading from the buffer, ..., (n-1), (n). , (n+1), . . . indicate the number of the frame to be transmitted.

Next, the operation will be explained. On the transmitting side, one frame of digital image data 2, which is continuously input from the camera 1 at camera synchronization intervals, is written to one side of an input double buffer 3 (hereinafter, the double buffer will be referred to as DB). At this time, writing of the previous frame data and reading of the frame data before the previous are performed in the transmission DB 4, and as soon as these are completed, the input DB 3 is switched between reading and writing, and the image data is read out for encoding. Note that the input 2 from the camera 1 during this period is not written to the input buffer 3 and is omitted. Then the input on the other side
Write one frame worth of image data from the next camera 1 to DB3 (side), and repeat the same operation. Next, the image data read from the input DB 3 is encoded by the variable length encoder 5 and transmitted.
Write to one side (referred to as side) of DB4. Meanwhile, on the opposite side (side), the image data of the previous frame is read out and transmitted to the transmission line 11. Sending DB4
As soon as the reading/writing is completed, the reading/writing is switched, and the written data is read and transmitted. Repeat the same action below. If the encoding is variable length and the transmission time changes, the time from the start of reading from the input DB3 to the end of writing to the transmission DB4 can be made smaller than the minimum value of the transmission time to transmit without reducing transmission efficiency. It can be performed.

On the other hand, the receiving side receives the received data.
Write to one side (referred to as the side) of DB6. On the opposite side (side), the data of the previous frame is read out for decoding, and the reading is finished first. When writing is completed, reading and writing of the reception DB 6 is switched, reading of the written data and writing of the next data are started. Repeat the same action below. Next, the data read from the reception DB 6 is decoded by the variable length decoder 7 and written to one side (referred to as the side) of the output DB 8. On the opposite side (side), the previous frame data is repeatedly read in synchronization with the monitor 9, and the image output 10
shall be. The output DB 8 switches between reading and writing at the end of the next monitor output after writing, reads the written data, and outputs it to the monitor 9. Output DB
Writing to 8 starts when the next decoded data arrives. Repeat the same action below.

In the conventional video transmission device as described above, as shown in FIG. The transmission time of the previous frame and the frame before the previous frame (transmission DB4
The frame drop interval (interval from W(n) to W(n+1) in input DB3) should be approximately equal to the sum of R(n-1) and R(n-2)) minus one camera synchronization time.
is the transmission time of the frame before the previous one (R(n
-2)). Also, the time of the frame played on monitor 9 on the receiving side (output
It can be seen that the repetition time of R(n) of the DB8 is approximately the reception time of the next frame (the time of W(n+1) of the receiving DB6).

[Problem that the invention seeks to solve]

Since the conventional video transmission device is configured as described above, frames are dropped at different time intervals for each frame adaptively depending on the state of the transmission path on the transmitting side.
The playback time of the same frame on the receiving monitor generally differed, leading to problems such as jerky movements.

This invention was made in order to solve the above-mentioned problems, and it is possible to adaptively drop frames depending on the condition of the transmission path without reducing transmission efficiency, and to reproduce a dropped frame image as a smooth image. The purpose of this invention is to obtain a moving image transmission device that can transmit images.

[Means for solving problems]

The moving image transmission device according to the present invention controls reading and writing of an input buffer and switching thereof based on a synchronization signal of a camera and a switching signal of a transmission buffer,
An input buffer control means updates and writes the image data from the camera frame by frame and switches between reading and writing from the next frame after the transmission buffer is switched, and an output buffer control means controls the output buffer based on the monitor synchronization signal and the reception buffer switching signal. The apparatus is equipped with an output buffer control means for controlling reading and writing and switching thereof, and making the number of times the same frame is repeatedly read in the output buffer correspond to the writing time of the previous frame to the receiving buffer.

[Effect]

In this invention, since a different time interval for each frame dropped by the input buffer corresponds to the readout time of the previous frame read out from the transmission buffer depending on the state of the transmission path, the reception buffer By controlling the number of times the same frame is repeatedly read out in the output buffer in accordance with the write time, a frame-dropped image can be reproduced as a smooth image without reducing transmission efficiency.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. Note that the same reference numerals are used for the same or equivalent parts as in the conventional example, and the explanation thereof will be omitted.

FIG. 1 is a block diagram showing the configuration of an embodiment. In the figure, 15 is an input double buffer control device provided on the transmitter 20 side, which corresponds to the input buffer control means of the present application, and transmits the camera synchronization signal 12. Based on the double buffer switching signal 13, an input double buffer control signal 16 is output to control reading/writing and switching of the input double buffer 3.
On the other hand, 17 is an output double buffer control device provided on the side of the receiver 21, which corresponds to the output buffer control means of the present invention, and outputs an output double buffer control signal 19 based on the monitor synchronization signal 14 and the receiving double buffer 18 to control the output double buffer. Based on the switching signal 18, an output double buffer control signal 19 is output to control reading and writing of the output double buffer 8 and switching thereof.

Next, the operation of the embodiment configured as above will be explained with reference to the timing chart shown in FIG.

On the transmitting side, digital image data 2 that is continuously input from the camera 1 at camera synchronization intervals is repeatedly written to one side (referred to as the side) of the input DB 3 for each frame. The previously written data is erased and updated during the next write. Input DB3 is sent
Switching is performed at the next camera input break after writing and reading of DB4 is completed, and the last written data is read. At the same time, writing starts on the opposite side (side), and the same operation is repeated thereafter. The data read from the input DB 3 is thereafter transmitted in the same manner as in the conventional example. In this case, by making the time obtained by adding one frame time of the camera to the time from the start of reading from input DB 3 to the end of writing to transmission DB 4 smaller than the minimum value of the transmission time, transmission can be performed without reducing transmission efficiency. can.

On the receiving side, the operation of the receiving DB 6 is the same as in the conventional example. The data decoded by the variable length decoder 7 is written to one side of the output DB 8, and on the other side (side), the data of the previous frame is repeatedly read out in synchronization with the monitor 9, and the image output data 10 Output as . At this time, the number of reads corresponding to the reception time of the previous frame, that is, the write time of the reception DB 6 (equal to the transmission time, that is, the read time of the transmission DB 4) is stored in advance, and only that number of times is output. Thereafter, reading and writing of the output DB8 is switched, and the same operation is repeated thereafter. However, if writing of the next frame to the output DB 8 is not completed even after the number of reads of the output DB 8 has been exceeded, increase the number of reads; , the reading from the reception DB 6 is delayed, the number of times the output DB 8 is read is reduced, and the image output 10 is adaptively output continuously.

In the moving image transmission device of the above embodiment, from FIG. 2, the time from the image input from the camera 1 to the start of transmission on the transmitting side and the frame drop interval are
Transmission time of previous frame (R(n-
1)). In addition, since the time of the frame played back on the monitor 9 on the receiving side is controlled to be approximately the reception time of the previous frame (W(n-1) of the reception DB 6), these times are approximately equal (the transmission time reception time). Therefore, a frame-dropped image can be reproduced as a smooth image without reducing transmission efficiency.

In the above embodiment, a double buffer is provided as the output buffer, but if it is difficult to time the writing and reading, it may be possible to use three or more buffers for control. The same applies to other buffers.

〔Effect of the invention〕

As described above, according to the present invention, reading and writing of the input buffer and switching thereof are controlled based on the synchronization signal of the camera and the switching signal of the transmission buffer,
An input buffer control means updates and writes the image data from the camera frame by frame and switches between reading and writing from the next frame after the transmission buffer is switched, and an output buffer control means controls the output buffer based on the monitor synchronization signal and the reception buffer switching signal. By providing an output buffer control means that controls read/write and switching thereof, and makes the number of times of repeated reading of the same frame in the output buffer correspond to the writing time of the previous frame to the receiving buffer, the frame can be transferred without reducing transmission efficiency. This has the effect of providing a moving image transmission device that can reproduce dropped images as smooth images.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a moving picture transmission device according to an embodiment of the present invention, Fig. 2 is a timing chart of the same, Fig. 3 is a block diagram showing a conventional moving picture transmission device, and Fig. 4 is a timing chart of the same. It is. 1 is a camera, 2 is digital image input data, 3
is an input double buffer, 4 is a transmitting double buffer, 5 is a variable length encoder, 6 is a receiving double buffer, 7 is a variable length decoder, 8 is an output double buffer, 9 is a monitor, 10 is image output data, 11 is a transmission line, 12 is a camera synchronization signal, 13 is a transmission double buffer switching signal, 14 is a monitor synchronization signal, 1
5 is an input double buffer control device (input buffer control means); 16 is an input double buffer control signal;
17 is an output double buffer control device (output buffer control means), 18 is a receiving double buffer switching signal, 19 is an output double buffer control signal, 20 is an image transmitter, and 21 is an image receiver. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 The input section from the camera and the transmission section to the transmission path are equipped with an input buffer and a transmission buffer in which storage areas for one frame of digital image data from the camera are multiplexed, and the above image data is variable-length encoded and transmitted. It is equipped with an image transmitter for transmitting data to the transmission channel, a receiving buffer and an output buffer similar to those described above in the receiving section from the transmission channel and the output section to the monitor, and the variable length encoded image data is variable length decoded and monitored. and an image receiver that outputs the image data to the camera, and according to the state of the transmission path, the storage areas of the buffers are alternately switched to read and write, and the image data from the camera is dropped in frames. In the device, reading and writing of the input buffer and switching thereof are controlled based on the synchronization signal of the camera and the switching signal of the transmission buffer, and the image data from the camera is updated and written frame by frame, and the next time the transmission buffer is switched. an input buffer control means for switching between reading and writing from the frame, and controlling reading and writing and switching of the output buffer based on a synchronization signal of the monitor and a switching signal of the receiving buffer, and controlling the number of times the same frame is repeatedly read from the output buffer to the receiving buffer. 1. A moving image transmission device comprising: an output buffer control means that corresponds to the writing time of the previous frame.