JPH02166979A - Television sound transmitting and receiving system, transmitter and receiver - Google Patents

Abstract

PURPOSE:To balance a video and a sound by transmitting the same sound by using both FM modulation and PCM sound multiplexing and switching both demoduled sound signals in correspondence to the S/N of a transmitted video signal in a reception side. CONSTITUTION:In a transmission side, a VSB-AM modulator 5 and FM modulator 7 are provided and the same sound is transmitted by the FM modulated wave signal of a sound carrier in a television transmission band and a PCM sound multiplexing signal in the horizontal and/or vertical flyback period of the video signal. In the reception side, a BL multiplexing signal sampling device 14, sound PCM decoder 18 and FM demodulator 20, etc., are provided and a television sound signal is respectively demodulated by the transmitted FM modulated wave signal and PCM sound multiplexing signal. Then, in response to the detected value of a bit error rate for the PCM sound, the two demodulated sound signals are switched and used. Thus, when the S/N is satisfactory, the PCM sound is used and when the S/N is degraded, the sound is switched to FM sound. Then, the video and sound can be balanced over the wide range of the S/N.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a television audio transmission/reception system, and in particular to the combined use of Folder transmission and PCM transmission of audio signals.

(Summary of the Invention) The present invention relates to a television audio transmission/reception system, and on the transmitting side, the same audio is transmitted through FM modulation of an audio carrier wave within the television transmission band, and horizontal and/or vertical blanking of a video signal. It is transmitted using two methods of multiplexing PCM audio within the period, and on the receiving side, the demodulated audio signal of the image transmission method is automatically switched and used according to the S/N of the transmitted video signal. are doing.

As a result, when the reception S/N of the video signal deteriorates and the reception error of PCM audio becomes large and becomes unusable, it is automatically switched to demodulated audio to prevent the audio signal quality from deteriorating.

(Prior Art) Conventionally, for example, NTS was used to transmit television audio signals.
A method that transmits FM-modulated audio carrier waves within the transmission band, such as C-2, or a method that multiplexes PCM audio as a digital signal during the horizontal and/or vertical retrace period, such as the MUSE method for high-definition television. A transmission method has been devised and implemented. The former is resistant to noise during transmission, but is susceptible to transmission distortion, resulting in lower sound quality than the latter. Furthermore, although the latter has high sound quality, it is susceptible to S/N deterioration.

(Problems to be Solved by the Invention) In the method of multiplexing and transmitting PCM audio on a television signal, there is a problem in balancing the quality of video and audio when the S/N deteriorates during transmission. In the case of video, the deterioration of image evaluation due to deterioration of S/N is relatively gradual, but in the case of PCM audio, error correction codes are used to improve the deterioration of audio quality due to noise, but the error rate is corrected. There is a drawback in that voice quality deteriorates rapidly when the correction capability of the code is exceeded. As a result, when the S/N is low, the quality of audio deteriorates more than that of video. Figure 2 shows S in PCM audio.
The relationship between /N (horizontal axis) and bit error rate (vertical axis) is shown for reference.

On the other hand, the sound quality of the normal NTSC audio signal, that is, the audio signal that is group-modulated on the audio carrier wave, is slightly lower, but the FM
Since it is a modulation method, it is relatively resistant to noise.

(Means for Solving the Problems) Therefore, in view of the above-mentioned problems, an object of the present invention is to use PCM audio when the S/N is good, and switch to FM audio when the S/N deteriorates. , (2) It is an object of the present invention to provide a television audio transmission/reception system that can balance video and audio over a wide range of S/H by taking advantage of the advantages of audio and PCM audio and compensating for their drawbacks.

In order to achieve this object, the television audio transmission and reception system of the present invention transmits and receives television audio signals, and on the transmitting side, the same audio is transmitted as an F14 modulated wave signal of an audio carrier wave within the television transmission band, The PCM audio multiplexed signal is transmitted within the horizontal and/or vertical retrace period of the video signal, and on the receiving side, the transmitted F1 modulated wave signal and the PCM audio multiplexed signal are transmitted, respectively. Demodulates the television audio signal and P
The present invention is characterized in that the two demodulated audio signals are switched and used in accordance with the detected value of the bit tap rate of the CM audio.

Further, the television audio transmitting device of the present invention is a transmitting device used in the transmitting/receiving system of the present invention, and the device converts the television audio signal into PCM and converts the television video signal into horizontal and/or vertical retrace lines. means for multiplexing in a period, means for modulating a video carrier wave with the multiplexed signal, means for group modulating an audio carrier wave with the same audio signal as the television audio signal, the modulating means, and the F
The present invention is characterized by comprising means for performing M modulation and means for mixing and transmitting both output signals.

Furthermore, the television audio receiving device of the present invention is a receiving device used in the transmitting/receiving method of the present invention, and the device is capable of receiving the transmitted FM modulated wave signal and the PC.
means for demodulating the television audio signal from the M audio multiplexed signal, means for detecting the bit error rate of PCM audio, and the two demodulated audio signals according to the detected bit error rate values. The present invention is characterized by comprising means for switching and outputting the FM sound and means for synchronizing the timing of the FM sound and the PCM sound.

(Examples) The present invention will be described in detail below by way of examples with reference to the accompanying drawings.

FIG. 1 shows a block diagram of a configuration of an embodiment of a transmitter/receiver according to the system of the present invention, and this embodiment is based on a normal NTSC transmission system.

According to the configuration shown in the first diagram, on the transmitting side, the input video signal (R
, G, B) are input to NT by video encoder 1.
SC encoded. On the other hand, the input audio signal is divided into two parts, one of which is converted into a digital signal with PCM encoding and an error correction code added by the audio PCM encoder 2, pulse amplitude modulated by the PAM waveform shaper 3, and then filtered through a roll-off filter. The waveform is shaped by the BL multiplexing circuit 4 and multiplexed in the horizontal and/or vertical retrace period of the output signal from the video encoder 1. This multiplexed signal is VSB-
The 4M modulator 5 amplitude modulates the television video carrier wave into a vestigial sideband form.

The other side of the input audio signal is an audio PCM encoder 2, P
After being delayed by the delay device 6 by the delay time of the PCM voice signal generated by the AM waveform shaper 3, etc., the voice carrier wave is FM-modulated by the FM modulator 7. The output of the VSB-4M modulator 5 and the output of the FM modulator 7 are combined by a combiner 8, amplified by an amplifier 9, and sent to a transmission line.

On the other hand, on the receiving side, the signal transmitted via the transmission path is first intensified by the amplifier 10 to the required level [11, and then the signal is
distributed into two signal paths. A video signal from the signal on one of the signal paths is extracted by a band pass filter BPFII, demodulated by a video detection circuit I2, and then passed through a low pass filter LP.
The baseband of the video signal is extracted via F13. After that, the BL multiplex signal extractor 14 extracts the signal corresponding to the PCM audio multiplexed during the retrace period of the video signal, and after shaping the waveform in the waveform shaper 16, the level determiner 1
At step 7, the level is determined and returned to a digital signal of zero or one, and then returned to the original audio signal at an audio PCM decoder I8. After the P (J audio signal) multiplexed during the retrace period is extracted by the BL multiplex signal extractor 14, the video signal is extracted by the video decoder I5.
It is SC decoded and becomes the original three primary color video signals of R, G, and B.

Next, from the signal distributed to the other signal path by the output of the amplifier 10, the audio carrier wave that has been FM modulated by the band pass filter BPF 19 is taken out, and is FM demodulated by the FM demodulator 20 to produce the original audio. After being converted back into a signal, it is delayed by a delay device 21 in order to adjust the time difference with the lIc4 audio signal.

The FM demodulated audio signal and the PCM demodulated audio signal thus obtained are selected by the switching switch 23 and output as an audio signal on the receiving side. The changeover switch 23 operates according to the result of the bit error rate determination 22 of the audio PCM decoder 18. That is, when performing error correction in the audio PCM decoder 18, the number of errors to be corrected is counted, and when the error rate is large, the changeover switch selects the FM demodulated audio signal, and when the error rate is small, the changeover switch selects the PCM demodulated audio signal. .

The basic transmission method of the embodiments described above is NT.
SC method, but it is not limited to this method, PCM in other horizontal and/or vertical retrace periods
The system of the present invention can be applied to any television transmission system that can multiplex audio.

(Effect of the invention) As described in detail above, according to the method of the present invention, F.
By using both M voice and PCM voice in combination, it is possible to simultaneously obtain the high quality of PCM voice during high S/N transmission and the gradual voice quality deterioration due to FM voice during low S/N transmission. It is possible to realize balanced television audio transmission of video and audio over a wide range of S/N.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of the configuration of an embodiment according to the system of the present invention, and FIG. 2 is a diagram showing the relationship between S/N and bit error rate in PCM audio. 1... Video encoder 3... PCM waveform shaper 5 ・VSB-AM conversion ma 7... FM modulator 9, lO... Amplification, etc. 12... Video detection circuit 14... BL multiplexing Signal extractor 16... Waveform shaper 18... Audio PCM decoder 22... Error rate determination

Claims (1)

[Claims] 1. When transmitting and receiving television audio signals, on the transmitting side, the same audio is transmitted to the FM modulated wave signal of the audio carrier wave within the television transmission band and the horizontal and/or vertical video signal. transmitting the PCM audio multiplexed signal within the retrace period, and on the receiving side, demodulating the television audio signal using the transmitted FM modulated wave signal and the PCM audio multiplexed signal, respectively; A television audio transmission/reception system characterized in that the timings of the two demodulated audio signals are adjusted according to a detected value of a bit error rate of PCM audio, and then the signals are switched for use. 2. A transmitting device used in the transmission/reception system according to claim 1, wherein the device converts a television audio signal into PCM and multiplexes it in the horizontal and/or vertical retrace period of a television video signal; means for modulating a video carrier wave with the multiplexed signal; means for FM modulating the audio carrier wave with the same audio signal as the television audio signal; and output signals from both the modulating means and the FM modulating means. What is claimed is: 1. A television audio transmitting device characterized by comprising means for mixing and transmitting. 3. A receiving device used in the transmitting/receiving method according to claim 1, wherein the device receives the transmitted FM modulated wave signal and the P.
means for demodulating the television audio signal from a CM audio multiplexed signal, means for detecting a bit error rate of PCM audio, and the two demodulated audio signals according to the detected bit error rate values; 1. A television audio receiving device comprising means for switching and outputting.