JP2912643B2 - Audio signal demodulator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio demodulation circuit for demodulating an audio signal in a high-definition television (hi-vision) receiver.

2. Description of the Related Art The high-definition television (Hi-Vision) system currently displays fine television images on a large wide screen and provides audio using audio signals transmitted by digital pulse modulation (DPCM). In recent years, various countries have been attracting interest in the technology, which seeks new attractiveness such as power and realism that cannot be obtained by television broadcasting. As one method of band-compressing the high-definition television signal, a MUSE (Multipul Sub-Nyquist Sampling Encodi
ng) method is proposed by the Japan Broadcasting Corporation (NHK). For details of the contents, see Yuichi Ninomiya et al., “One-channel satellite transmission system for high-definition television,” IEICE, Vol.
D, No.4PP.647-654 (1985), or Watanabe, Takegahara “Quasi-instantaneous companding DPCM for high-definition audio baseband transmission
Method "is shown in the Institute of Electronics, Information and Communication Engineers (March, 62).

Hereinafter, an example of a conventional audio signal demodulation circuit will be described with reference to the drawings.

FIG. 2 is a block diagram of a conventional audio signal demodulation circuit. In FIG. 2, 21 is a bit deinterleave circuit, 22 is an error correction circuit, 23 is a word deinterleave circuit, 24 is a decompression circuit, 25 is a range detection / error correction circuit, 26
Is an interpolation circuit, 27 is an integration circuit, 28 is a synchronization detection circuit, and 29 is a mute circuit.

Regarding the audio signal demodulation circuit configured as described above,
The operation will be described below.

First, a synchronization pattern is detected by a synchronization detection circuit 28 to synchronize an audio input signal having 1350 kb / S as one frame. If synchronization is achieved, a synchronization lock signal (Hihg) is output, and synchronization is not achieved. In this case, a synchronous lock signal (Low) is output and applied to the mute circuit 29. Further, the bit deinterleaving circuit 21 processes the bit deinterleaving of the audio input signal on the transmission side. Next, the error correction circuit 22 performs one error correction and two error detection in the normal mode, and performs two error correction and three error detection in the enhanced mode.
Further, the output signals from the error correction circuit 22 for detecting two errors in the normal mode and for detecting three errors in the enhanced mode are input to the interpolation circuit 26 as interpolation signals. On the other hand, the output of the error correction circuit 22 is de-interleaved by the word de-interleaving circuit 23 on the transmission side. The range detection / error correction circuit 25 detects a range bit indicating the degree of compression of the audio signal, and performs one error correction.
Perform error detection. Next, in the expansion circuit 24, the output signal of the word deinterleave circuit 23 is
Is decompressed in accordance with the range bit detected by (1). Next, in the interpolation circuit 26, the output of the decompression circuit 24 is subjected to the previous sample value of the same channel and the average value interpolation or pre-interpolation by the interpolation signal output from the error correction circuit 22 described above. Next, an interpolation circuit 26 which is a difference signal
Integrate the output of. Only when the synchronization lock signal output from the synchronization detection circuit 28 described above is Low (for example, synchronization unlock forced mute), all the outputs are output by the mute circuit 29.
Set to Low and output as audio signal.

Next, the range detection / error correction circuit will be described in more detail. The range signal indicating the degree of compression of each channel performed on the transmission side is included in the audio input signal. further,
A correction code is also added to the range bit, and the range error correction circuit 32 performs one error correction and two error detection, and outputs an error detection signal when an error is detected. Next, the output of the range error correction circuit 32 and the one-frame delay circuit 33
The output delayed by the frame (1 msec) is input to the switching circuit 34. When an error is detected by the error detection signal output from the range error correction circuit 32, the switching circuit 34 detects the error of the output signal of the delay circuit 33 which is a signal delayed by one frame (previous frame). If not,
The output signal of the range error correction circuit 32 is output to the decompression circuit 24 as a range bit.

However, in the above-described configuration, when the C / N is deteriorated due to distortion of a transmission line or rainfall, an error occurs in a range bit of an audio signal, and when correction cannot be performed, the previous frame is not used. Since the audio signal is expanded by the range bit of the above, the degree of error of the audio signal becomes large, and the demodulated audio has a problem that a pop noise or the like occurs.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an audio signal demodulation circuit that reduces popping noise and the like and demodulates appropriate audio to a viewer even when C / N is deteriorated due to distortion of a transmission line or rainfall. The purpose is to provide.

Means for Solving the Problems To achieve the above object, an audio demodulation circuit according to the present invention comprises:
When a range bit error is detected, a range bit minimum circuit for outputting range bit information so as to set the range bit to a minimum so that the expansion rate of audio data is minimized is provided.

Operation The present invention, with the above-described configuration, causes C / N degradation due to distortion of a transmission line or the like due to rainfall, and when an error is detected in a range bit, an expansion process is performed using the output of the range bit minimum circuit as a range bit. Since it is configured to apply the sound, it is possible to demodulate the sound in which the pop noise or the like is reduced.

Embodiment An audio signal demodulation circuit according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a range detection / error correction circuit of an audio signal demodulation circuit according to an embodiment of the present invention. In FIG. 1, 11 is a range detection circuit, 12 is a range error correction circuit, 13 is a range bit minimum circuit, 14 is a switching circuit, and 15 is a display circuit.
The difference from the configuration of the prior art shown in FIG. 2 is that a range bit minimum circuit 13 and a display circuit 15 are provided.

The operation of the range detection / error correction circuit of the audio signal demodulation circuit configured as described above will be described below with reference to FIG.

A range bit indicating the degree of compression of each channel is included in the audio input signal, and this is detected by the range detection circuit 11. Further, a correction code is also added to this range bit, and the range error correction circuit 12 performs one error correction and two error detection, and when an error is detected, outputs an error detection signal.

Next, the output of the range error correction circuit is changed by the range bit minimum circuit 13 so that the range bit is changed to a value having the smallest expansion degree in each mode (for example, range 7 in A mode, range 5 in B mode) and output. The output of the range error correction circuit 12 and the output of the range bit minimum circuit 13 are switched by the switching circuit 14 according to the error detection signal output from the range error correction circuit 12 and output. In other words, if an error is detected in the range bit, the output of the range bit minimum circuit 13 which is the range bit having the minimum degree of expansion is selected, and if no error is detected, the output of the range error correction circuit is output as it is. . In addition, when an error is detected in the range bit, the display circuit 15 displays on the display device or the like that the range bit has an error.

As described above, according to the present embodiment, by providing the minimum range bit circuit, the C / N
If a range bit error due to C / N deterioration is detected even if the deterioration of the NR occurs, the popping sound in the demodulated voice can be reduced by supplying the value of the smallest expansion degree as the range bit to the expansion circuit. Further, by providing a display circuit, a viewer can be warned even if a pop noise occurs, so that a problem in the transmission system such as a problem in the direction of the antenna can be warned.

Effects of the Invention As described above, according to the present invention, by providing the minimum range bit circuit, it is possible to reduce the pop noise even when distortion of the transmission line or the like or deterioration of the C / N occurs.

[Brief description of the drawings]

FIG. 1 is a block diagram of a range detection / error correction circuit of an audio signal demodulation device in one embodiment of the present invention, FIG. 2 is a block diagram of an audio demodulation circuit, and FIG. 3 is a block diagram of a conventional range detection / error correction circuit. It is a block diagram. 11: Range detection circuit, 12: Range error correction circuit, 13
... The smallest range bit circuit, 14... Switching circuit, 15... Display circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-173600 (JP, A) JP-A-62-151246 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 20/18 H04B 14/04

Claims (2)

(57) [Claims] 1. A bit deinterleave circuit for canceling bit interleave processing of a voice input signal on a transmission side, an error correction circuit for correcting an error of an output of the bit deinterleave circuit, and A word deinterleaving circuit that takes an output as an input and resolves word interleaving that is being processed on the transmission side, a range detection / error correction circuit that detects the range of the output of the error correction circuit and performs error correction, An expansion circuit for expanding the output of the word deinterleave circuit by a range bit of the output of the correction circuit; an interpolation circuit for interpolating the output of the expansion circuit with an interpolation signal that is a second output of the error correction circuit; An audio signal demodulation device comprising: an integration circuit for integrating an output of an interpolation circuit; The circuit includes a range bit minimum circuit, a range detection circuit, a range error correction circuit, and a switching circuit that outputs one of an output of the range error correction circuit and an output of the range bit minimum circuit. When there is a range bit error, select and output the output of the range bit minimum circuit that generates the range bit with the smallest expansion degree in each transmission mode, and output the range error correction circuit when there is no range bit error. A quasi-instantaneous compression / expansion DPCM audio signal demodulator characterized in that an output is selected, output and supplied to an expansion circuit. 2. The quasi-instantaneous companding DPCM audio signal demodulator according to claim 1, further comprising display means for displaying that there is a range bit error when a range bit error is detected.