JPH0222467B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a PCM signal processing device.

It has been widely known that high quality recording and playback is possible by converting analog audio signals to PCM (digitalization). Since the occupied frequency band of the signal increases due to PCM conversion, it is considered to use a VTR (video tape recorder) with a wide transmission frequency band for recording and reproduction.

In this case, in order to use a VTR that originally records and plays back television signals, it is necessary to convert the PCM audio signal (hereinafter sometimes abbreviated as PCM signal) into the same signal format as the television signal. It will be done. In other words, the rotary head type
When using a VTR, a horizontal synchronization signal and a vertical synchronization signal similar to television signals are added, and time axis compression processing is performed so that a data deletion period corresponding to the horizontal and vertical retrace period is formed. It will be done.

When reproducing an audio signal recorded in this manner, a video signal related to the reproduced audio signal may be simultaneously reproduced. In this case, while operating the VTR for video signals, the VTR for audio signals is connected to a PCM signal processing device, and the basic clock from the basic clock generation circuit built in this PCM signal processing device is used to operate the VTR for audio signals. It is conceivable to operate them in synchronization.

However, in this case, the VTR for video signals
Since the VTR for the audio signal and the audio signal are asynchronous,
For example, there is a problem in that the mouth movements of the narrator in the reproduced video do not match the reproduced audio, and so-called lip sync cannot be achieved.

In order to solve this problem, it is necessary to
The same standard composite synchronization signal, for example, an internal synchronization signal within a broadcasting station, is supplied to each of the VTR and audio VTR for synchronized operation, and the PCM
It is conceivable to synchronize the PCM signal processing device based on a synchronization signal reproduced from a VTR that reproduces a converted audio signal. In this case, each
The VTR itself is servoed by the in-station synchronization signal, and synchronized playback is performed to some extent.

However, for PCM audio signal playback,
Since the synchronization signal reproduced from the VTR contains a slight jitter component compared to the local synchronization signal, the basic clock is formed from this reproduction synchronization signal to operate the PCM signal reproduction processing circuit, and the reproduction processing of the PCM audio signal is performed. That is, when a digital audio signal is converted into an analog audio signal, a clock containing jitter is used, and problems such as distortion in the reproduced analog audio signal still remain.

The present invention relates to a PCM signal processing device for recording and playing back PCM signals converted into a signal format similar to that of a television signal using a VTR, and in particular to video playback and audio playback by the PCM signal processing device. The purpose of this paper is to propose a configuration that synchronizes the PCM signals and when dubbing PCM signals by a PCM signal processing device.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a standard composite synchronization signal generator installed, for example, in a broadcasting station. 2 is for video signal
4 indicates a VTR, and 4 is for PCM audio signals.
Showing a VTR. The VTR 2 has a video input terminal 3i and a video output terminal 3o. Similarly, VTR4
has an input terminal 5i and an output terminal 5o.
6 indicates a PCM signal processing device, and its output terminal 7
o is coupled to the input terminal 5i of the VTR 4, and its input terminal 7i is coupled to the output terminal 5o of the VTR 4. Input terminal 8i for PCM signal processing device 6
An analog audio signal is supplied from the VTR 4, this audio signal is converted into PCM and recorded by the VTR 4, the PCM signal reproduced by the VTR 4 is demodulated, and the reproduced audio signal appears at the output terminal 8o.

The VTR 2 and the PCM signal processing device 6 are synchronized using the composite synchronization signal Sr from the standard composite synchronization signal generator 1 mentioned above as a reference. That is, when the video signal from the video input terminal 3i is recorded by the VTR 2, the composite synchronization signal Sr is applied to the synchronization signal input terminal of the VTR 2. On the other hand, the composite synchronizing signal Sr is also applied to the synchronizing signal input terminal of the PCM signal processing device 6, and a basic clock synchronized with this composite synchronizing signal Sr is formed.

FIG. 2 shows the recording system of this embodiment, showing a configuration for forming a basic clock synchronized with the composite synchronization signal Sr.

In FIG. 2, reference numeral 11 indicates a composite synchronization signal input terminal to which a composite synchronization signal Sr is applied. A vertical synchronization separation circuit 14 is connected thereto.

The PLL circuit 12 is composed of a variable frequency generator 15, a frequency divider 16, a phase comparator 17, and a low-pass filter 18, and a basic clock _CP1 is derived from the variable frequency oscillator 15. Also provided is a crystal oscillator 19 which generates a basic clock _CP2 of the same frequency as the basic clock _CP1 .

The two basic clocks CP ₁ and CP ₂ are applied to one input of AND gates 20a and 20b, respectively. The positive phase output Q of the monostable multivibrator 13 is supplied to the other input terminal of the AND gate 20a, and the negative phase output is supplied to the other input terminal of the AND gate 20a.
0b is supplied to the other input terminal of AND gate 2
Each output of 0a and 20b is supplied to a synchronizing signal forming circuit 22 via an OR gate 21. A vertical synchronization signal from the vertical synchronization separation circuit 14 is applied as a reset signal to the synchronization signal forming circuit 22 to achieve frame synchronization.

The composite synchronization signal from the synchronization signal forming circuit 22 is applied to the synthesis circuit 23, and the basic clock CP ₁ or
CP ₂ via this synchronization signal forming circuit 22,
It is added to the PCM modulation circuit 24. This PCM modulation circuit 24 performs signal conversion processing such as sampling of the analog audio signal from the input terminal 8i, A-D conversion of the sampling output, time axis compression, and addition of an error correction code, and the output signal is sent to the synthesis circuit 24. is supplied to A PCM signal having the same signal form as the television signal appears at the output terminal 7o of the combining circuit 23.

The positive phase output Q of the above-mentioned monostable multivibrator 13 becomes "1" during the period when the composite synchronization signal Sr is applied, and conversely becomes "0" during the period when the composite synchronization signal Sr is not applied. Therefore, during the period when the composite synchronization signal Sr is applied, the PLL is
The basic clock _CP1 formed by the circuit 12 is supplied to a synchronization signal forming circuit 22, which generates a composite synchronization signal.
During the period when Sr is not applied, the basic clock _CP2 from the crystal oscillator 19 is supplied to the synchronization signal forming circuit 22. In this way, the PCM signal, which has the same signal format as the television signal, is recorded by the VTR 4. Since the VTR 4 performs a recording operation in synchronization with the vertical synchronization signal included in this PCM signal, the VTR 4 is indirectly synchronized with the composite synchronization signal Sr.

During reproduction, the VTR 2 performs a reproduction operation in synchronization with the composite synchronization signal Sr.

FIG. 3 shows the reproduction system of this embodiment, and since the portion surrounded by a chain line in the figure is exactly the same as the configuration shown in FIG. 2, a redundant explanation thereof will be omitted.

In the case of reproduction, a subtracter 33 is provided in place of the synthesis circuit 23 in FIG. 2, and a PCM demodulation circuit 34 is provided in place of the PCM modulation circuit 24.

In this PCM demodulation circuit 34, signal conversion processing such as error correction, time axis expansion, and DA conversion is performed, contrary to that in the PCM modulation circuit 24 described above.

PCM played from VTR4 is input to input terminal 7i.
An encoded audio signal is supplied. On the other hand, the composite synchronization signal Sr is input from the input terminal 11, and the composite synchronization signal formed by the synchronization signal forming circuit 22 by the same operation as that described in the operation explanation of FIG. Supplied. Input terminal 7i
Similarly, the reproduced PCM signal supplied to the subtracter 33
The composite synchronization signal, which is not necessary for the audio signal, is removed from the reproduced PCM signal.

The output signal of this subtracter 33 is the PCM demodulator 3
It is supplied to one input end of 4. The other input terminal of this PCM demodulation circuit 34 is connected to a synchronization signal forming circuit 2.
The basic clock from 2 is given, and the composite synchronization signal
Based on this basic clock synchronized with Sr,
The above-described inverse conversion process is performed, and a reproduced analog audio signal is output to the output terminal 8o. At the same time, a signal synchronized with the composite synchronization signal Sr is supplied to the VTR 4 via the PCM signal processing device 6.

According to one embodiment of the present invention described above, for video signals
The reproduced video signal obtained at the video output terminal 3o of the VTR and the reproduced audio signal obtained at the output terminal 8o of the PCM signal processing device are synchronized, which not only prevents the time relationship between the video and the audio from shifting, but also prevents the audio signal from shifting. Since there is no need to directly supply a standard composite synchronization signal to the VTR used for the VCR, the connections between the various devices can be simplified, the circuit configuration can be simplified, and the distortion components contained in the reproduced audio signal can be reduced.

In the above embodiment, the synchronization signal forming circuit 22 is reset by the vertical synchronization signal separated from the composite synchronization signal Sr to establish frame synchronization, but even if frame synchronization is not performed, the video and If the initial start point coincides with the audio, there will be a maximum deviation of only 1/30 (second), and there will be almost no audible problem.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIGS. 2 and 3 are block diagrams showing its recording system and reproduction system. 1 is a standard composite sync signal generator, 2 and 4 are
VTR, 6 is a PCM signal processing device, 11 is a composite sync signal input terminal, 12 and 19 are basic clock generation circuits, 13 is a composite sync signal detection circuit (retrigger type monostable multivibrator), 22 is a sync signal forming circuit, 24 is a PCM modulation circuit, and 34 is a PCM demodulation circuit.

Claims (1)

[Claims] 1. An analog audio signal is input, the analog audio signal is converted into a digital audio signal, and the digital audio signal is sent to a recording/reproducing device to be recorded and reproduced. A PCM signal processing device configured to perform reverse conversion to obtain an analog audio signal includes a composite sync signal input terminal into which a composite sync signal similar to a sync signal included in a television signal is input; a first basic clock generation circuit that generates a first basic clock based on the reference clock; a second basic clock generation circuit that generates a second basic clock having a frequency equal to that of the first basic clock; a composite synchronous signal detection circuit that detects whether or not the composite synchronous signal is input to the signal input terminal; and selects the first basic clock or the second basic clock according to the detection signal from the composite synchronous signal detection circuit. and a signal forming circuit that converts the analog audio signal into a digital audio signal in the form of a signal to be recorded by the recording/reproducing device, using the output of the basic clock selection circuit as a reference. A PCM signal processing device characterized in that conversion and inverse conversion processing is performed based on the output of the basic clock selection circuit.