Disk Player for Displaying Recorded Audio Signals

This invention relates to a disk player which can play LDs, CDs and CDVs, or to a disk player which can play CDs and CDVs.

In disk players of these types, a video signal is read from a disk and then displayed on a monitor, whereas a digital audio signal read from the disk is subjected to D/A (digital-to-analog) conversion for outputting an analog audio signal. Further, data such as time, chapter and TNO which are recorded on the disk, are decoded so that they can be superimposed as character displays on the monitor.

On the other hand, the CD format has a sub-code data region. If digital picture graphs or sentences of character data are recorded in the sub-code data region, then they can be decoded so as to be displayed on the monitor.

Thus, in playing a compact disk with a disk player capable of playing LDs, CDs and CDVs or with a disk player capable of playing CDs and CDVs, characters such as time data can be displayed on the monitor in the system, or still pictures of image data previously stored in memory can be displayed on the monitor. Furthermore, in the case where sub-codes have been recorded on the compact disk, then digital graphs or characters of the sub-codes can be displayed.

However, in an audio reproduction with a compact disk having no sub-codes, nothing can be displayed on the monitor, or a meaningless still picture can be displayed; that is, it cannot be said that the disk player is sufficiently utilized.

In view of the foregoing, the present invention has been developed. The present invention provides a signal processing system, which, during audio reproduction, a signal processing operation is carried out with image data representing the circuit characteristics of the audio data reproducing system as a video output, whereby the monitor is efficiently used. According to the present invention, during audio reproduction, the power level of the audio signal is displayed on a television monitor over the frequency band of the audio signal. Additionally, audio signal levels for right and left channels, and the frequency characteristics of the equalizer may be displayed.

This invention is based on the fact that audio signals outputted by a decoder are digital data, and is intended to provide a disk player with the feature of displaying musical waveforms on a television monitor (e.g., of a NTSC system) similar to the case of an oscilloscope.

According to the present invention, a disk player includes a signal processing means which, in playing a disk having audio data, uses the audio data as an output of a video data reproducing system. The signal processing means is designed so that a digital audio signal outputted by a decoder is divided into frames with an interval therebetween, if necessary. The frames are sampled for each of the pictures handled by the video data reproducing system.

FIG. 1 is a block diagram showing one embodiment of the invention.

FIG. 2 is a time chart showing a sampling operation of an audio output so that the audio output is displayed as a picture for frames with an interval therebetween.

FIG. 3 is an explanatory diagram showing a display on a television monitor.

FIG. 4 is a graphical representation indicating the sampling data of frame (1) in FIG. 2.

One embodiment of the invention will now be described with reference to the accompanying drawings.

As shown in FIG. 1, a signal from a system controller 1 is used to drive a tracking actuator or focus actuator (not shown) so that a RF signal is read with a pickup 2. The RF signal thus read is applied through a RF amplifier 3 to a video data demodulating system 4 and to a digital data demodulating system 5.

In the video data demodulating system 4, the RF signal is demodulated into a video signal by demodulating circuit 41, and the video signal is applied through a time axis correcting circuit 42 to a video signal processing circuit 43. The horizontal synchronizing signal, vertical synchronizing signal, and control data included in the video signal outputted by the demodulating circuit 41, are extracted and separated by a separating circuit 44. In synchronization, for instance, with the extracted horizontal synchronizing signal, a local oscillator (e.g., a voltage-controlled oscillator (VCO)) 45 provides an oscillation output and a frequency division signal. A time axis control circuit 46 receives the oscillation output and the frequency division output, and the horizontal synchronizing signal and the color burst signal contained in the video signal provided by the time axis correcting circuit 42 are compared to obtain the phase difference thereof. As a result of this comparison, the time axis control circuit applies a control signal, corresponding to the phase difference, to the time axis correcting circuit 2 to thereby subject the video signal to time axis correction. The time axis corrected video signal is applied through the video signal processing circuit 43 to a video output terminal 6.

The video signal processing circuit 43 carries out a video muting operation of inhibiting the outputting of a video signal, an operation of superimposing character data provided by a character generator, and an operation of inserting images according to image data.

Since it is necessary to process a PCM audio signal separately according to a CD region and a video region, the digital data demodulating system 5 includes an equalizer circuit 51 and an amplifier 52 for CD regions, and an EFM signal extracting circuit 53, an equalizer circuit 54 and an amplifier 55 for video regions. The digital data demodulation system 5 further includes a select switch 56 for selecting between either a first system consisting of the equalizer circuit 51 and the amplifier 52, or a second system consisting of the EFM signal extracting circuit 53, the equalizer circuit 54 and the amplifier 55. A change-over instruction is applied to the select switch 56 by the system controller 1.

The reason why the two systems are employed is that if, in the recording operation, the digital signal is superposed on the FM-modulating video signal as it is, then the EFM signal will adversely affect the low frequency components of the FM video signal, and therefore the recording operation is carried out under the conditions that the EFM signal is lower by several tens of decibels (dB) than the carrier although they are equal in modulation degree. In other words, an EFM signal for a CD region and an EFM signal for a video region are different in frequency characteristic and in amplitude when reproduced, even if they are the same signal and accordingly it is necessary to provide different systems to process them.

In a CD region reproduction, the reproduced RF signal is an EFM signal, and it is compensated in frequency characteristic by the equalizer circuit 51 having a predetermined equalizing characteristic, and the compensated signal is amplified with a predetermined gain by the amplifier 52. On the other hand, in a video region reproduction, only an EFM signal included together with an FM video signal in the reproduced RF signal is extracted by the EFM signal extracting circuit 53 having a low pass filter and it is compensated in frequency characteristic by the equalizer circuit 54 having an equalizing characteristic which is different from that of the equalizer circuit 51, and it is amplified at a large gain by the amplifier 55.

Thus, in the video region reproduction, the EFM signal obtained has a frequency characteristic and an amplitude which are substantially equal to those of the EFM signal obtained in the CD region reproduction.

The reproduced EFM signal is subjected to EFM demodulation by a demodulation-correction circuit 57, and then written in a memory such as a RAM. The signal written into the RAM is used for a de-interleaving operation through the transmission of data to and from the RAM in response to a clock signal from a reference clock generator 58, and a parity check using parity in the data. The binary 16-bit digital audio signal thus demodulated and corrected is processed by an audio signal processing circuit 59 comprising a D/A converter and a deglitcher circuit, and then applied to audio output terminals 7R and 7L.

The above-described audio signal is further applied to a digital signal processing section 8, where it is processed to provide audio output waveforms for right and left channels with the horizontal axis as a time axis on the monitor (See FIG. 3). Video data obtained by conversion of the digital audio signal together with other ordinary data such as time data, chapter and TNO is laid out when necessary, and supplied, as a video signal, to the video signal processing circuit. The above-described video data is obtained as follows: The audio signal is divided into frames, with an interval (determined from a processing time) therebetween, when necessary, and the frames are sampled according to a picture handled in the video reproduction system (See FIG. 2). For instance in the case where, in sampling data at 44.1 KHz, one sample is extracted every 100 sampling operations, and 100 samples extracted from one picture, thus providing an audio output waveform, renewal for the picture takes 0.23 sec=(1/C 44.1.times.10.sup.3).times.100.times.100. Renewal for the waveform display at a speed of this order is effective in displaying waveforms on the monitor, and the merit in waveform observation of a digital oscilloscope can be confirmed on the monitor.

The waveforms for right and left channels may be displayed with time on the monitor as shown in FIG. 3, however, the waveforms may be displayed over the time access in such a manner that they overlap each other, or they may be displayed as Lissajous figures for right and left channels. In this case, an effect on measurement or on entertainment can be expected.

As was described above, according to the invention, the signal processing means is so designed that, in converting a digital audio signal into video data, the digital audio signal is sampled with an arbitrary period and displayed in correspondence with an optional picture handled by the video data reproducing system. Therefore, in the CD reproduction, the video monitor which converts video signals into pictures can display musical waveforms as in the case of an oscilloscope.