JPS5837815A - Pcm sound recorder and reproducer - Google Patents

Abstract

PURPOSE:To prevent assuredly the misjudgement between a carrier dropout and a horizontal synchronizing signal, by detecting the carrier dropout when a PCM signal is reproduced and then setting forcibly the level of the synchronizing signal at a prescribed value. CONSTITUTION:A detector 15 detects the amplitude of the carrier signal of the output of an equalizer 4, and delivers an output ''1'' when a carrier dropout is produced and then ''0'' in the normal mode, respectively. A gate 16 is controlled by the output ''1'' or ''0''. When the output is ''1'', the synchronizing signal given from a comparator 12 is cut off and ''1'' is forcibly fed to a terminal X. While the synchronous signal is fed to the terminal X as it is when the output is ''0''.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PCM recording and reproducing apparatus for recording and reproducing audio signals according to the PCM method using a video tape recorder (hereinafter referred to as a VTR) or a part thereof.

The PCM signal format shown in the consumer PCM encoder/decoder technology file determined by the Japan Electronics Industry Association is shown in FIGS. 1 and 2.

Figure 1 shows the vertical signal part of the PC°M signal format that conforms to standard television signals.
) shows the data arrangement and structure of the odd field as shown in Figure 1(b).
) shows the data arrangement and structure of the even field as shown in Figure 1 (C
)' shows details of the vertical synchronization signal and equalization pulse signal in Fig. 1(a), and Fig. 1(d) similarly shows details of the vertical synchronization signal and equalization pulse signal in Fig. 1(b). ing.

FIG. 2 shows the arrangement and structure of the horizontal signal section of the PCM signal format, and FIG. 2(a) shows the arrangement and structure of one horizontal signal section in units of bits. This signal waveform is based on a television signal, but the signal obtained by slicing this signal into levels, that is, the PCM data signal part, is shown in FIG. The part is shown in FIG. 2(C).

As can be seen from these, a data synchronization signal "101o#" is added to the beginning of each horizontal signal section, and a white reference signal is added to the end, and one horizontal signal section consists of 168 bits.Here, 526 line standard TV is used. However, regarding the signal former node compliant with the 626-line standard television system, the signal former node itself is the same, with only some bit configurations being different. Therefore, it can be considered in the same way as the case of 526 lines.

Figure 3 shows a conventional PCM signal that records and plays back such PCM signals.
This shows part of the playback system of the CM recording and playback device.

In FIG. 3, A is the head section of channel 1, B is the head section of channel 2, 1 and 2 are head amplifiers that amplify the output of the channel section jJB, and 3 is head amplifiers 1 and 2.
4 is an equalizer circuit, 5 is a limiter, 16 is an FM demodulator, 7 is a carrier removal filter, 8 is an amplifier, 9 is a waveform shaping filter, 10 is an automatic gain control circuit, 11 is a The clamp circuit 12 is a comparator, and the clamp circuit 11 and the comparator 12 cause the second
The synchronizing signal shown in Figure (C) is regenerated and output to terminal The data signal is reproduced and output to terminal Y.

Note that the 0 point in Figure 3 indicates the F reproduced from the magnetic tape.
The M carrier signal appears, and the equalizer output of the carrier signal appears at point D.

In conventional PCM recording and playback devices, the second
As can be seen from the figure, in order to synchronize one horizontal period when reproducing the PCM signal, the "O" period of the horizontal synchronization signal shown as i to i in Fig. 2 (C) is detected, and thereby one horizontal It is necessary to synchronize the periods, but in that case, if a carrier dropout occurs and the output of terminal One.

If the signal then returns to normal, it will be mistakenly determined to be a horizontal synchronization signal, causing a problem in that the synchronization of subsequent PCM signal processing will be disrupted.

The present invention provides a PCM recording/playback device that solves these problems with a simple configuration.

An embodiment of the present invention will be described below with reference to FIGS. 4 and 6.

In FIG. 4, parts having the same functions as those in FIG. 3 are denoted by the same reference numerals, and explanations thereof will be omitted.

16 detects the amplitude of the carrier signal appearing at the output point of the equalizer circuit 4, and when carrier dropout occurs, generates 1j' as the output Z; when normal,
In other words, it is a carrier dropout detector that generates "0" as output Z when there is no carrier dropout. 16. is controlled to open and close by the output Z of the carrier dropout detector 15, and when the output Z is "0"
, the synchronizing signal from the comparator 12 is output to the terminal This is a gate circuit that sends out 1''.

In this way, even if carrier dropout occurs, the synchronization signal at terminal can be prevented.

Note that the gate circuit 16 can be specifically configured with a tri-state circuit G1 as shown in FIG.

As described above, the present invention detects carrier dropout when reproducing a PCM signal, and when dropout occurs, the level of the synchronization signal is forcibly set to 1''. can be reliably prevented from being mistakenly judged as a horizontal synchronization signal.

[Brief explanation of drawings]

Figures 1 (a) to (d) are diagrams showing the format of a PCM signal, Figures 2 (a) to (C) are diagrams showing the configuration of one horizontal signal section, and Figure 3 is a diagram showing the conventional PCM recording and playback. FIG. 5 is a block diagram showing a part of the reproduction system of the apparatus, FIG. 4 is a block diagram of an embodiment of the present invention, and FIG. AB...Head section, 1, 2...Head amplifier, 3...Mixer, 4...Equalizer circuit, 5...Limiter -Circuit, 6...
FM demodulator, 7: Carrier removal filter, 8: Amplifier, 9: Waveform shaping filter, 10: Automatic gain control circuit,
11... Clamp circuit, 12... Comparator, 13... Amplifier, 14... Comparator,
16...: Carrier dropout detector, 16
・・・・・・Gate circuit.

Claims (1)

[Claims] P played from magnetic tape for video tape recorder
'A carrier dropout detector detects the carrier amplitude of the CM signal to detect the presence or absence of carrier dropout, and the opening/closing is controlled by the output of the carrier dropout detector, and when there is no carrier dropout, the regenerated synchronization A PCM recording and playback device characterized in that it is equipped with a gate circuit that outputs a signal as it is and forcibly sets a synchronization signal to "1" when there is a carrier dropout.