SU582588A1 - Device for compressing digital television signals - Google Patents

Description

The invention relates to information transmission and storage systems and can be used in transmission and recording devices of broadcast television. A device for compressing digital television signals is known, comprising a series-connected analog-to-digital converter, a bitwise comparison unit, a transmission symbol selector unit, and a coding unit, the output of the transmission unit selector unit being connected to the second input of the bit comparison unit via serially connected memory control unit and memory block. However, the known device has a low signal ratio. The purpose of the invention is to increase the signal compression ratio. For this, a device for compressing digital television signals comprising a series-connected analog-to-digital converter, a one-bit comparison unit, a transmission symbol selection unit and a coding unit, wherein the output of the transmission symbol selection unit is connected to the second input of the one-phase comparison unit through serially connected control units memory and memory block, a sync code generation block and a reference level setting block, whose input is 5 10 15 20 25, are entered; - 30 dinene with an analog-to-digital input and the output is connected to the auxiliary input of the memory unit directly to another input of the coding unit through the synchronization code generation unit, with the auxiliary output of the memory unit connected to another input of the memory management unit. The drawing shows a structural electrical circuit for compressing digital television signals. The proposed device comprises serially connected analog-to-digital converter 1, block 2 of bitwise comparison, block 3 of selection of a transmitted symbol and block 4 of coding, the output of block 3 of selecting a transmitted symbol being connected to the second input of block 2 of bitwise comparison via serially connected block 5 of memory control tue and memory unit 6, unit 7 for setting the reference level, the input of which is connected to the input of the analog-digital converter 1, and the output is connected to the auxiliary input of the memory unit 6 directly o, to another input of the coding unit 4 through the synchronization code generation unit 8, the auxiliary output of the memory unit 6 being connected to another input of the memory management unit 5.

A device for compressing digital television signals works as follows.

Memory block 6 is n counting triggers, where is the number of bits of the source code. The occurrence on one of the p outputs of block 3 for the selection of a transmitted symbol of the logical level 1 translates the counting trigger of memory block 6, which corresponds to this output, to the state opposite to the previous one. All triggers of the memory block representing the code bits younger than the changed one are set to the state opposite to the new state of the trigger in which the change is written. This operation is performed by the memory management unit 5. The output of the block 3 for the selection of the transmitted symbol is connected to the block 4 of the coding, which is assembled according to the tuner scheme with n inputs. From the output of coding block 4, the binary code is read into the communication channel, where /: log2n.

Block 7 installation reference level. is a standby multivibrator that generates signals that periodically set the triggers of memory block 6 to a certain state. For example, when transmitting a television signal to the input of the reference level setting unit 7, a full television signal is received from which the selector, which is part of the reference level setting unit 7, extracts the sync signal. The multivibrator of the reference level setting unit 7 is triggered by the front of the horizontal (frame) sync pulse and generates a signal setting the triggers of the register of memory unit 6 to the state corresponding to the dimming level in the television signal. Therefore, at the time of the occurrence of the quenching interval in the television signal, the triggers of memory block 6 on the transmitting and receiving sides of the device are set to the same position. Consequently, at subsequent moments of time there is no need to transmit information about the level of the digit code that has changed, but it is enough to transmit information about the presence of a symbol change in any bit (. Bits) of the code, with which the counting trigger of the corresponding block code bit is 6, the memory of the receiving side is set to the opposite state. Since there is no information on the level of the changed code discharge during transmission, due to the presence of failures in the communication channel, tracks can occur during reception

mistakes. The resulting error tracks are corrected at the instants of the occurrence in the dimming signal, when on the receiving side the state of all code bits is known. However, if a complete television signal is encoded (along with sync pulses), then due to the occurrence of failures and, as a result, the error tracks during reception, it is impossible to isolate the sync signal and, therefore, reproduce the transmitted message. Therefore, in the proposed device, the information about the clock signal is transmitted by a special code, which is generated by the synchronization code generation unit 9. Generator start

the synchronization code generation unit 8 is provided from the output of the reference level setting unit 7. It is quite obvious that in the described device additional efficiency in transmission does not lead to a deterioration in the quality of reproduced images. In a device for compressing digital television signals, the compression ratio of the signal increases, since the proposed device makes it possible to reduce, in comparison with the prototype, the amount of information transmitted by one bit in each sample. The quality of the reproduced images is maintained.

Claims (1)

1. USSR author's certificate No. 543192, cl. H 04L 25/49, 1975.