JPH0412071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital television audio multiplex control signal processing device for a television receiver.

As the signal processing of television receivers changed from analog processing to digital processing,
Costs are being reduced by reducing the number of peripheral parts, and audio multiplex signals are also being digitized. In the audio multiplex control signal processing section, 31.5k
It is determined whether it is a monaural signal or a multiplex signal based on the level of the Hz subchannel signal, and if it is a multiplex signal, whether it is a different program broadcast or a stereo broadcast is AM modulated with a 55.1kHz subcarrier.
The control signals of 922.5Hz and 982.5Hz are determined, and after determining whether it is monaural or multiplexed, it is determined whether it is a different program broadcast or a stereo broadcast.

Therefore, it depends on whether there is a 31.5kHz sub-channel signal or not.
922.5Hz and 982.5Hz sent on 55.1kHz subcarrier
It is more stable for the receiver to determine whether it is a monaural heterogeneous program broadcast or a stereo broadcast based on the presence or absence of a control signal. Conventionally, the former judgment as to whether it is monaural or multiplex is made using a digital comparator for the 31.5 kHz sub-channel signal, and judgment is made based on whether the signal exceeds or does not exceed a threshold level, so the judgment pulse is periodically generated. The judgment output is extremely unstable due to impulsive noise, etc. Therefore, the present invention attempts to stably detect whether a monaural signal or a multiplex signal is present based on the cumulative addition level by cumulatively adding 31.5KHz sub-channel signals for a certain period of time. An embodiment of the present invention will be described with reference to the drawings.

In Fig. 1, 1 is the SIF audio intermediate frequency detection output, which is an analog audio multiplexed composite signal.This composite signal is digitized by the A/D converter 2 and converted to a PCM signal 3, and the converted signal is converted into a digital BPF. (Bandpass filter)
4 to extract the 31.5kHz sub-channel signal component. This extracted 31.5kHz sub-channel signal component 5 is full-wave rectified by a full-wave rectifier circuit (consisting of an exclusive OR gate) 6, and the full-wave rectified PCM signal 7 is sent to a 31.5kHz level detection block 8. is input. This level detection block 8
is composed of a cumulative adder and a digital comparator, and the cumulative adder is composed of a full adder 9 and D-type flip-flops 11 and 13.
1 and the input of the full-wave rectifier circuit 7 are added to perform cumulative addition. Then, cumulative addition is performed at the period of the clear pulse 18 in FIG. 2, and the final state of the cumulative addition output is held by the D-type FF 13 using a latch pulse slightly before the clear pulse 18. At this time, if there is a 31.5 kHz sub-channel signal, the waveform of the output 12 of the D-type flip-flop 11 will be a triangular wave as shown in 25, as shown in 24 in FIG.
It becomes a triangular wave like . Therefore, the presence or absence of the 31.5 kHz sub-channel signal is determined by latching the cumulative addition output level such as 25 or 26 with the D-type flip-flop 13 before the clear pulse and comparing it with the threshold level of 27 with the digital comparator 15. can. Also, since cumulative addition is performed, even if impulsive noise comes in, the impulsive noise can be ignored in the cumulative addition result, so whether there is an audio multiplex signal or a monaural signal is as stable as the elbow. It can be determined whether there is Note that 21 is a clock generator.

The present invention as described above converts an audio multiplex composite signal detected from a television audio intermediate frequency signal into an A/
A D converter converts it into a PCM signal, a digital bandpass filter extracts the sub-channel FM signal from the composite signal, and the sub-channel signal is passed through a digital rectifier circuit to perform full-wave rectification. The signals are cumulatively added for a certain period of time by an accumulative adder circuit consisting of a full adder and a D-type flip-flop with a clearing function, and the presence or absence of the sub-channel signal is determined based on the accumulated level. Erroneous judgments will not be made due to impulsive noise, and stable judgments can be made.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a television audio multiplex control signal processing device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the device. 2...A/D converter, 4...Digital band pass filter, 6...Full wave rectifier circuit, 8...Level detection block, 9...Full adder, 11, 13...
...D-type flip-flop, 15...digital comparator, 21...clock generator.

Claims (1)

[Claims] 1 Convert the audio multiplexed composite signal detected from the TV audio intermediate frequency signal into a PCM signal using an A/D converter, extract the sub-channel FM signal from the composite signal using a digital bandpass filter, and convert the sub-channel signal into a digital signal. By passing it through a rectifier circuit, full-wave rectification is performed, and the full-wave rectified signal is cumulatively added for a certain period of time in an accumulative adder circuit consisting of a full adder and a D-type flip-flop with a clear function. 1. A television audio multiplexing control signal processing device, characterized in that a signal for determining whether or not a sub-channel signal exists is determined based on the level of the sub-channel signal.