JP3364936B2 - TV signal transmission device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TV signal transmitting apparatus, and more particularly to a TV signal transmitting apparatus for transmitting a TV signal by an FM system. 2. Description of the Related Art A conventional TV signal transmission apparatus includes:
The pre-emphasis circuit applies the emphasis specified in CCIR recommendation 405-1 to the TV signal to be transmitted, and then transmits the signal after FM modulation, and the receiving side converts the demodulated TV signal into a de-emphasis circuit. To receive a TV signal. [0003] As described above, conventionally, a TV signal is transmitted by emphasis specified by CCIR. However, as shown in FIG. 3, when the TV signal that changes sharply (FIG. (A)), to the signal
In order to include many high-frequency components, so that the instantaneous frequency by multiplying the emphasis exceeds a predetermined pass band (FIG. (C)). And the passband
Signal components that exceed
Therefore , impulse-like noise is generated in demodulation on the receiving side (FIG. 2B). Because of this, especially the brightness
When the average level is low, that is, when the screen is dark,
There is a problem that impulsive noise is conspicuous . An object of the present invention is to provide a TV signal transmission device capable of reducing the effects of impulsive noise generated by applying emphasis to the TV signal which changes sharply. [0005] A TV signal transmitting apparatus according to the present invention is a TV signal transmitting apparatus for transmitting a TV signal by the FM system, wherein the transmitting side comprises an average luminance level for each field of the TV signal. A luminance average detection unit that detects a value and outputs a signal indicating an average value, a variable pre-emphasis unit that changes an emphasis amount according to the signal indicating the average value, and an encoder that encodes the signal indicating the average value When,
A multiplexing unit that multiplexes a signal encoded by the encoder during a vertical blanking period of the TV signal,
The receiving side includes a separating unit for extracting the coded signal multiplexed in the vertical blanking period of the demodulated TV signal, a decoder for decoding the signal extracted by the separating unit, and a decoder for decoding the signal. changing the emphasis amount in accordance with the signal, the example Bei a variable de-emphasis unit for correcting the emphasis exerted by the variable pre-emphasis of the send side, before Symbol variable pre-emphasis unit and the variable deemphasis unit, When the average value of the luminance levels is small, the emphasis amount is reduced, and the operation is performed so as to increase the emphasis amount as the average value of the luminance levels increases. Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention. The luminance average detection unit 11 of the transmitter 1 outputs the TV signal S
An average value of the luminance level for each field of v is detected, and a signal D1 indicating the average value is output. The variable pre-emphasis unit 12 changes the emphasis amount according to the signal D1. The encoder 13 encodes the signal D1 to generate a signal D2
Output as The multiplexing unit 14 multiplexes the signal D2 during a vertical blanking period of the TV signal. The FM modulator 15
The carrier is FM-modulated with the output signal of the multiplexing unit 14. The output signal of the FM modulator 15 is sent out via the bandpass filter 16 and the transmitter 17. The FM demodulator 23 of the receiver 2 demodulates the signal received via the receiver 21 and the bandpass filter 22. The separation unit 24 extracts the signal D2 multiplexed in the vertical blanking period of the demodulated TV signal.
The decoder 25 decodes a signal D1 indicating the average luminance level from the extracted signal D2. The variable de-emphasis unit 26 changes the amount of emphasis according to the decoded signal D1, corrects the emphasis applied by the variable pre-emphasis unit 12 of the transmitter 1, and reproduces the TV signal Sv. The variable pre-emphasis unit 12
Changes the emphasis amount according to the average luminance level of each field of the TV signal as shown in FIG. That is, when the average value of the luminance levels is small, the emphasis amount is suppressed to be small, and as the average value of the luminance levels increases, the emphasis amount is increased. [0010] By doing so, the average value of the brightness level is low Itoki, means that when the dark screen, Enfu
By suppressing the amount of ASIC, even if emphasis is applied to a TV signal whose luminance level changes rapidly,
Signals beyond the passband cut by the bandpass filter
Demodulation on the receiving side because the energy of the signal component can be reduced
The occurrence of impulse noise due to reduces, impulse
Ru can be as inconspicuous Jo noise. As described above, according to the present invention, a variable pre-emphasis unit and a variable de-emphasis unit are provided on the transmission side and the reception side, respectively. The average value is detected, the pre-emphasis amount is adjusted according to the average value, and a signal indicating the average value is multiplexed on the TV signal and transmitted to the receiving side.
On the receiving side extracts the signal indicating the average value, Ri by the adjusting the de-emphasis amount in accordance with the average value, the receiving side by Rukoto over-emphasis TV signal changing sharply
Impulse noise generated by demodulation can be reduced ,
Ru can be as inconspicuous a scan-like noise.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram for explaining an operation of a variable pre-emphasis unit shown in FIG. 3A and 3B are diagrams for explaining a problem when emphasis is applied to a TV signal, and FIG. 3A illustrates an example of a TV signal waveform in which an average value of a luminance level is low and luminance changes rapidly. b) shows an example of a demodulated waveform on the receiving side when conventional emphasis is applied to the TV signal shown in FIG.
(C) shows a conventional emphasis on the TV signal shown in ( a ).
2 shows an example of a frequency spectrum resulting from multiplication. [Description of Code] 1 Transmitter 2 Receiver 11 Brightness average detector 12 Variable pre-emphasis unit 13 Encoder 14 Multiplexer 24 Demultiplexer 25 Decoder 26 Variable de-emphasis unit Sv TV signal D1 Indicates the average value of the brightness level of the TV signal Signal D2 Signal obtained by encoding signal D1

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Claims (1)

(57) [Claims 1] A TV transmitting a TV signal by the FM system
In the signal transmission device, the transmission side detects a luminance level average value of each field of the TV signal and outputs a signal indicating the average value, and an emphasis amount according to the signal indicating the average value. A variable pre-emphasis unit for changing the average value, an encoder for encoding the signal indicating the average value, and a multiplexing unit for multiplexing the signal encoded by the encoder in a vertical blanking period of the TV signal. Is a separator for extracting the coded signal multiplexed during the vertical blanking period of the demodulated TV signal, a decoder for decoding the signal extracted by the separator, and a decoder for decoding the signal extracted by the decoder. A variable de-emphasis circuit for changing an emphasis amount according to a signal to correct the emphasis applied by the variable pre-emphasis unit on the transmission side. And a variable pre-emphasis unit and
And the variable de-emphasis unit controls the average of the luminance level.
When the average value is small, reduce the emphasis amount and
The emphasis amount increases as the average value of the degree level increases.
TVs each operating to increase
Signal transmission device.