JPH01138866A - Television signal digital transmission method - Google Patents

Abstract

PURPOSE:To attain the digital transmission of a television signal at a minimum transmission speed by using the least significant bit of a digital data corresponding to a signal front porch, a horizontal synchronizing signal and a back porch as a frame synchronizing bit. CONSTITUTION:In a frame of the television signal digital transmission method, the least significant bit Y0 among digital data Y0-Y8 after A/D conversion is replaced into a frame synchronizing bit F. As the frame synchronizing bit, '1', '0' alternate pattern is used and the digital data after A/D conversion is not converted but sent as it is. When the frame is detected from the frame synchronizing bit at the reception side, whether or not the frame synchronizing bit is included is discriminated by the signal after D/A conversion. Through the constitution above, the digital transmission of the television signal is applied at minimum transmission speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to digital transmission of television signals, which is characterized in that frame synchronization bits can be introduced.

Prior art Conventional television signal digital transmission method and 29.N
o, 6. pp. 684-691, (1983).

FIG. 2 shows a frame structure in this conventional television signal digital transmission method, and shows a 40-bit frame. F is a bit for frame synchronization, and Yo-Y8 is A/Y8 for one sample of television signal.
The digital data after D conversion, D0 to D2, are auxiliary data bits and will not be treated here. One word is 10 pits, which is the number of quantization pits of 9-bit A/D conversion data plus 1 bit.If the sampling frequency is f 3 Hz, and the serial data transmission speed is fD b/B, then , fp = fB X (9+1). D0~
Even without the auxiliary data bits of D2, the transmission rate f
D is f p = 9 x f 3 x 37 / 36
becomes.

Problems to be Solved by the Invention However, in the above example, the transmission rate fD is the product of the number of quantization bits and the sampling frequency, and the minimum required 9Xf
s transmission speed. In the former case, the increase in transmission speed is large, and in the latter case, although the increase in transmission speed is small, a complicated circuit is required for speed conversion of 37/36.

The present invention has been made in view of the above, and an object of the present invention is to provide a television signal digital transmission method in which the transmission rate is the product of the number of quantization bits and the sampling frequency, and in which frame synchronization bits can be introduced.

Means for Solving the Problems The present invention provides a method for converting the least significant bit of digital data corresponding to all or part of the front porch, horizontal synchronizing signal, and back porch of a television signal out of the digital data after A/D conversion. This is a television signal digital transmission method in which frame synchronization bits are used as frame synchronization bits, and frame synchronization bits are not transmitted when transmitting digital data corresponding to other television signals.

Function As described above, the present invention uses the least significant bit of digital data obtained by A/D converting all or part of the front porch, horizontal synchronizing signal, and back porch of a television signal as a frame synchronization bit, and uses the other bits as frame synchronization bits. In this case, only A/D converted digital data is transmitted, so the transmission speed is given by the product of the number of quantization bits and the sampling frequency. Transmit signals digitally.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a frame structure of a television signal digital transmission method according to an embodiment of the present invention. This is the part of the digital data after /D conversion, and (b) is the other part. F is a bit for frame synchronization, and Y is the least significant bit of the digital data Y0 to Y8 after A/D conversion. This is a replacement for . In the case of digital transmission of television signals, an alternating pattern of 1'',''Oj is generally used as frame synchronization bits.

In the digital data part shown in FIG. 1(b), A/
The digital data after D conversion is transmitted as is without being converted at all. In this embodiment, the frame synchronization bits have an alternating pattern of 1'' and ``OJ'', so the frame length is 18 bits for 2 samples.

On the receiving side, if a frame can be detected from the frame synchronization bits, it can be determined whether the television signal after D/A conversion contains the frame synchronization bits, and it is possible to determine whether the frame synchronization bits are out of synchronization during a period in which there are no frame synchronization bits. However, other than that, the same circuit as in the case where frame synchronization bits are always transmitted may be used.

In the case of an NTSC television signal, the width of the horizontal synchronizing signal is approximately 5 μB, and if the front porch and part of the back porch are added, a synchronization pull-in time of approximately 10 μS is provided. On the other hand, if the sampling frequency is 14.3MHz, which is four times the color subcarrier frequency, the average synchronization pull-in time is approximately 6.3MHz.
This is 7 μs, and on average, synchronization can be achieved with one horizontal synchronization signal.

The reason why the least significant bit is used as a frame synchronization bit is because the receiving side does not have to remove the frame synchronization bit before D/A conversion. This is because there is no practical problem as long as the signal is modulated.

As described in detail, according to the present invention, no extra time slot for frame synchronization bits is added, so the transmission speed is given by the product of the number of quantization bits and the sampling frequency.
Digital transmission of television signals is possible at the minimum transmission speed, and its practical effects are significant.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a frame configuration diagram of a television signal digital transmission method according to an embodiment of the present invention, and FIG. 2 is a conventional frame configuration diagram. F... Frame synchronization bit, Yo-Y8...
...Digital data.

Claims (1)

[Claims] When a television signal is A/D converted and transmitted as digital data, among the digital data after A/D conversion, the front porch of the television signal, horizontal synchronization signal,
A television signal digital transmission method characterized in that the least significant bit of digital data corresponding to all or part of a back porch is used as a frame synchronization bit.