JPH04141863A - Compressed sound signal reproducing device - Google Patents

Abstract

PURPOSE:To decide the termination of sound sequence without detecting the control code of a subsequent track by invalidating a subsequent sound track number which a control code detection means detects by means of a sound track where a control flag is detected by means of a control flag detection means. CONSTITUTION:A system control circuit 54 gives a detection instruction to the control code detection circuit 53 and a sector type detection circuit 10. A sequence discrimination circuit 55 compares the control codes from the outputs of the control code detection circuit 53 and discriminates the connection of the sound track. When the sector type detection circuit 10 detects a type-3 in the track, the 'subsequent sound track number' is invalidated from the output of the control code detection circuit 53 and information on the sound sequence is outputted to the system control circuit 54. Thus, the reproduction of sound can be terminated without accessing to the track of the 'subsequent sound track number'.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a compressed audio signal reproduction apparatus for reproducing a time-base compressed audio signal recorded on a magnetic disk by, for example, a video floppy recorder.

Conventional technology In recent years, instead of cameras using film.

A video floppy recorder that records still images on a 2-inch floppy disk (hereinafter referred to as a video floppy) has been commercialized, and in the future, a function to record audio signals as well as still images for a predetermined period of time will be added, and various products will be available. It is expected that it will be produced.

The compressed audio signal reproducing apparatus as described above will be described below with reference to the drawings.

FIG. 4 is a block diagram showing a video floppy audio recording device as an example of a device for recording a time-base compressed audio signal, and FIG. 5 shows a recording format of the audio signal. Figure 5 (a
) shows the track format, (b) the sector format, and (c) the sector type.

This will be explained below using FIG. 4.

As is well known, the video floppy 40 has 50 concentric tracks facing toward the inside of the outer shell, and a video signal (still image) or an audio signal is recorded on each track. Also, the rotation speed of the video floppy 40 is 3 e OOr
pffh That is, since it rotates once every 1/60 seconds, a video signal is compressed into one field in the case of a video signal, and an audio signal is compressed into 1760 seconds on the time axis and recorded on each track. The time axis compression ratio of the audio signal is 320 times, 640 times, 1280 times.
Three double modes are available, and each track can record approximately S seconds, approximately 10 seconds, and approximately 20 seconds of audio signals. When the time axis compression ratio is 640 times, the audio signal recorded on one track is approximately 10 seconds long, but when recording audio signals longer than that, multiple tracks are used to record, and each track is is recorded with control codes such as the first audio track number and the subsequent audio track number of a series of audio signals added.

As shown in FIG. 4, the audio signal is input from an input terminal 1 to a low pass filter (LPF) 30 and band-limited, and then input to a time axis conversion circuit 31.

The time axis conversion circuit 31 is well known and includes an A/D converter 32 that converts an analog audio signal into a digital signal, a memory 33 that stores the digital signal, and a D/A converter that converts the digital signal into an analog signal. It is constituted by a container 34.

The signal input to the time axis conversion circuit 31 is converted into a digital signal by the A/D converter 32. Thereafter, it is written into the memory 33 at the write clock frequency fw. After this writing is completed, the data is read out at the read clock frequency fr, and converted into an analog signal by the D/A converter 34. Time axis conversion rate K of time axis conversion circuit 31
c is expressed by the following formula.

Kc=fw/fr When Kc<1, the time axis conversion circuit 31 operates as a time axis compression circuit, and when Kc>1, the time axis conversion circuit 31 operates as a time axis expansion circuit.

During recording, the time axis conversion circuit 31 operates as a time axis compression circuit, and outputs a time axis compressed audio signal (hereinafter referred to as a compressed audio signal) that is time axis compressed to 1760 seconds.

An adder 35 adds a control code and a flag to this compressed audio signal. After that, a pre-emphasis circuit 36, an FM modulation circuit 37. The signal passes through an amplifier 38 and is recorded on a video floppy 40 by a magnetic head 39.

Next, the recording format of the audio signal will be explained using FIG. FIG. 5(a) is a diagram showing the track format. DSP is a data start point. The compressed audio signal is divided into four septa and recorded.
A space is provided between each sector. FIG. 4B is a diagram showing the sector format. The control code is information possessed by the audio signal, and includes the "first audio track number" and "subsequent audio track number" of the series of audio signals mentioned above, as well as the "track number where the corresponding video signal is recorded", 1 The same control code is recorded in each sector on the same track. The same compressed audio signal as the last part of the compressed audio signal of the previous sector is recorded in the overlap.

The start flag and end flag indicate the beginning and end of a sector, and serve as a time axis reference when reproducing a compressed audio signal.

Furthermore, although the start flag is a positive signal in FIG. 5(b), it becomes a negative signal when, for example, no compressed audio signal is recorded in this sector. Further, the end flag is a negative signal, but becomes a positive signal if, for example, recording of the compressed audio signal ends in this sector and does not continue to the next sector. That is, as shown in FIG. 5(C), the sector type is represented by the polarity of these two flags, and the sector is divided into four types. Type 1 continues with the next sector on the track, Type 2 continues with sector 0 of the following track at the end of the track. Also, type 3 means the sector ends, and type 4 means unused. However, in the control code of the track including type 3, "
"Subsequent audio track numbers" have no meaning.

The reproduction operation of a compressed audio signal recorded in the above format will be explained using FIGS. 6, 7, and 8.

In FIG. 6, 40 is a video floppy disk and 50 is a playback head. Reference numeral 51 denotes a head access section, which moves the reproducing head 50 to an arbitrary track. 5
2 is a demodulation circuit that amplifies and FM demodulates the signal read from the reproducing head 50. 31 is the time axis conversion circuit mentioned earlier, which operates as a time axis expansion circuit during playback, and expands the compressed audio signal captured at 1/60 seconds to 840 times in the 640 times mode, and sends it to the output terminal. 2 outputs an audio signal. A control code detection circuit 53 detects a control code recorded on the audio track and outputs its contents. 54 is a system control circuit which gives an access instruction to the head access unit 51 so that the playback head 50 accesses a desired track, gives a playback instruction to the time axis conversion circuit 31, and gives a playback instruction to the control code detection circuit 53. It gives a detection instruction. 55 is a sequence discrimination circuit, which compares control codes from the output of the control code detection circuit 53 and discriminates the connection of audio tracks;
It outputs audio sequence information to the system control circuit 55.

FIG. 7 shows a part of the control code of the compressed audio signal recorded on the video floppy 40.

FIG. 7(a) shows the "absolute track number," (b) shows the "first audio track number J," and FIG. 7(c) shows the "subsequent audio track number."

The reproduction operation of the video floppy 40 recorded as described above will be explained with reference to FIG. FIG. 8(a) shows the position of the reproducing head 50, and the shaded area indicates that it is moving. (b) shows the writing period of the compressed audio signal to the time axis conversion circuit 31 and the detection period of the control code, and (c) shows the reading period from the time axis conversion circuit 31. First, the system control circuit 54 gives an access instruction to the head access section 51 to move the playback head 50 to the first track. When the playback head 50 moves to the first track, the output of the playback head 50 is amplified by the demodulation circuit 53 and F
M is demodulated and output. And the system control circuit 54
By giving a reproduction instruction and a detection instruction to the time axis conversion circuit 31 (time axis expansion circuit) and the control detection circuit 53, the time axis conversion circuit 31 writes a compressed audio signal, and the control detection circuit 53 detects a control code. . The control detection circuit 53 outputs the contents to the sequence determination circuit 55, determines that the audio track following the first track is the second track, and outputs it to the system control circuit 54. The system control circuit 54
When the writing of the compressed audio signal for the track is completed, the second
The head access unit 51 is instructed to access the playback head 50 to the track. After the access is completed, a reproduction instruction and a detection instruction are given to the time axis conversion circuit 31 and the control detection circuit 53. Similarly to the first track, when the time axis conversion circuit 31 writes a compressed audio signal, the simultaneous control detection circuit 53 detects a control code. The control detection circuit 53 outputs its contents to the sequence discrimination circuit 55. The sequence determination circuit 55 determines that the audio track following the second track is the third track, and outputs the result to the system control circuit 54. When the writing of the compressed audio signal on the second track is completed, the system control circuit 52 instructs the playback head 5o to access the third track, and after the access is completed, the system control circuit 52 instructs the time axis conversion circuit 31 and the control detection circuit 53 to playback. and give detection instructions. Similarly to the first and second tracks, the time base conversion circuit 31 writes the compressed audio signal, and at the same time the control detection circuit 53 detects the control code. The control detection circuit 53 outputs its contents to the sequence determination circuit 55. The sequence determination circuit 55 determines, for example, from the "first audio track number" that the third track is a different audio sequence and the second track is the final audio track, and outputs this to the system control circuit 54.

The system control circuit 54 instructs the time axis conversion circuit 31 to reproduce up to the second track, and this series of reproduction operations ends when the audio signal of the second track is reproduced.

Problems to be Solved by the Invention However, in the conventional configuration described above, it is not possible to determine that the final audio track is the final audio track, and the track with the "successive audio track number" recorded in the control code is accessed, and the track of the control code is accessed. It was only after detection was performed that it was determined whether the previous tiger, RI, was the final audio tiger, RI or not.

Therefore, as shown in the above embodiment, if the track with the "subsequent audio track number" written in the control code of the final audio track is an audio track, the third
The compressed audio signal of the track was written,
The problem was that readout control of the time axis conversion circuit was extremely difficult.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an excellent compressed audio signal reproducing device that can determine the end of an audio sequence without detecting the control code of a subsequent track.

Means for Solving the Problems In order to achieve the above object, the compressed audio signal reproducing device of the present invention has a compressed audio signal that is time-base compressed and is divided into a plurality of tracks, and each track contains a series of divided audio signals. A record having an audio track recorded with a control code indicating the first audio track number and the subsequent audio track number of the signal, and a control flag indicating whether or not this is the last track of the divided compressed audio signal. a medium, a head for reproducing a compressed audio signal recorded on the track, an access means for moving the head to an optimal position on the medium, a reproducing means for obtaining an audio signal from the output of the head, and an output of the head. control code detection means for detecting the control code recorded on the audio track from the output of the head; control flag detection means for detecting the control flag recorded on the audio track from the output of the head; a system control means for instructing a track to be moved to, and for instructing the reproduction means, the control code detection means, and the control flag detection means to reproduce and detect an audio signal; and the control code detection means and the control flag detection means. The apparatus further includes a sequence determining means that receives the output of the system as an input, determines the connection of a plurality of audio tracks recorded on the recording medium, and appropriately outputs information on the connection of the audio tracks to the system control means.

Effect of the Invention With the above configuration of the present invention, the sequence determination circuit can determine whether the "subsequent audio track number" recorded in the control code is meaningful or not at the time of detection of the control code. This results in
It is possible to end audio playback without accessing the track of the "subsequent audio track number."

EXAMPLE A first example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a video floppy audio reproducing apparatus in one embodiment of the present invention.

In the figure, 40 is a video floppy disk, 50 is a playback head, and 51 is a head access section.
to any track. 52 amplifies the audio signal read out from the playback head 50 and FM
This is a demodulation circuit that performs demodulation. Reference numeral 31 denotes the time axis conversion circuit mentioned earlier, which operates as a time axis expansion circuit during reproduction. A control code detection circuit 53 detects a control code recorded on the audio track and outputs its contents.

The above is the same as the conventional example, and will not be explained here.

Reference numeral 10 denotes a sector type detection circuit, which detects whether sector type 3 exists in the track to be detected. 10a is a positive flag detection circuit that detects a flag with positive polarity, and 10b is a comparison circuit that compares it with a predetermined value. The number of positive flags included in the audio track having the following audio track is 4 including the start flag and the end flag. However, in a track including a type 3 sector, both the type 3 start flag and end flag are positive, so the number of positive flags is five. Therefore, by setting the predetermined value of the comparator circuit 10b to, for example, 5, it is possible to detect whether type 3 is present in the track. 54 is a system control circuit, and the playback head 50
In order to access a desired track, an access instruction is given to the head access unit 51, and the time axis conversion circuit 3
1 and a detection instruction to the control code detection circuit 53 and sector type detection circuit 10. 55 is a sequence discrimination circuit;
The control code is compared from the output of the control code detection circuit 53 to determine the connection of the audio tracks, but if the sector type detection circuit 10 detects type 3 in the track, the control code detection circuit 53, the "subsequent audio track number" is invalidated, and audio sequence information is output to the system control circuit 54.

FIG. 2 shows part of the control code of the compressed audio signal recorded on the video floppy 40.

Figure 2 (a) shows "first audio track number", (b) shows "
"Subsequent audio track number."

The reproduction operation of the video floppy 40 recorded as described above will be explained with reference to FIG. FIG. 3(a) shows the position of the reproducing head 50, and the shaded area indicates that it is moving. (b) is a writing period of the compressed audio signal to the time axis conversion circuit 31;
(C) shows the readout period from the time axis conversion circuit 31, the detection period of the control code detection circuit 53, and the detection period of the sector type detection circuit 10. First, the system control circuit 54 gives an access instruction to the head access section 51 to move the playback disk 50 to the first track. When the playback head 50 moves to the first track,
The output of the playback head 50 is amplified by a demodulation circuit 53 and converted into FM
It is demodulated and output. Then, the system control circuit 54 issues a reproduction instruction to the time axis conversion circuit 31 (time axis expansion circuit).
Further, a detection instruction is given to the control code detection circuit 53 and the sector type detection circuit 10. As a result, the time axis conversion circuit 31 writes the compressed audio signal, and the control code detection circuit 53 and sector type detection circuit 10 each start detection. The control code detection circuit 53 outputs the contents of the control code written on the first track to the sequence determination circuit 11. The sequence determination circuit 55 determines that the audio track following the first track is the second track, and outputs the result to the system control circuit 54.

When the writing of the compressed audio signal on the first track is completed, the system control circuit 54 causes the playback head 5 to write the compressed audio signal on the second track.
The head access unit 51 is instructed to access 0. After the access is completed, the time axis conversion circuit 31 receives a reproduction instruction,
A detection instruction is given to the control code detection circuit 53 and sector type detection circuit 10.

Similarly to the first track, the time axis conversion circuit 31 writes a compressed audio signal in response to a reproduction instruction, and the control code detection circuit 53 and sector type detection circuit 10 start detection. The control code detection circuit 53 outputs the contents of the control code written on the second track to the sequence determination circuit 11. Further, at this time, the positive flag detection circuit 10a detects five positive flags, and the comparison circuit 10b outputs to the sequence determination circuit 11 that type 3 exists in the second track. The sequence determination circuit 11 invalidates the fact that the audio track following the second track from the output of the sector type detection circuit 10 is the third track, and outputs to the system control circuit 54 that the audio sequence ends with the second track. .

The system control circuit 54 instructs the time axis conversion circuit 31 to reproduce up to the second track, and this series of reproduction operations ends when the audio signal of the second track is reproduced.

Effects of the Invention As is clear from the above embodiments, the present invention makes it possible to determine the end of an audio sequence without accessing the track of the "successive audio track number".
The readout operation of the time axis conversion circuit is also simplified, and the circuit can be configured simply.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a compressed audio signal reproducing device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the contents of a control code recorded on a video floppy, and FIG. An operation explanatory diagram for explaining the operation, FIG. 4 is a block diagram showing an example of a conventional recording device,
Figure 5 shows the format, Figure 5 (a) is a track format diagram, Figure 5 (b) is a sector format diagram, Figure 5 (C) is a waveform diagram showing sector types, and Figure 6 is a conventional 7 is an explanatory diagram for explaining the contents of the control code recorded on the video floppy, and FIG. 8 is an operational explanation for explaining the operation of the device. It is a diagram. 10... Sector type detection circuit, 10a... Positive flag detection circuit, 10b... Comparison circuit, 31
... Time axis conversion circuit, 40 ... Video floppy 50 ... Playback head, 51 ... Head access section, 52 ... Demodulation circuit, 53 ... Control code detection circuit, 54 ... System Control circuit, 55... Sequence discrimination circuit. Name of agent: Patent attorney Haruaki Koebi and two others

Claims (2)

[Claims] (1) A compressed audio signal subjected to time axis compression is divided into a plurality of tracks, and each track includes a control code indicating the first audio track number and the subsequent audio track number of a series of divided audio signals, and a recording medium having an audio track recorded with a control flag indicating whether or not it is the last track of a compressed audio signal; a head for reproducing the compressed audio signal recorded on the track; access means for moving the medium to an optimal position; playback means for obtaining an audio signal from the output of the head; control code detection means for detecting the control code recorded on the audio track from the output of the head; control flag detection means for detecting the control flag recorded on the audio track from the output of the head; and control flag detection means for instructing the access means to a track to which the head should be moved; A system control means for instructing a flag detection means to reproduce and detect an audio signal, and outputs of the control code detection means and the control flag detection means are input, and a connection between a plurality of audio tracks recorded on the recording medium is determined. death,
sequence determining means for appropriately outputting information on the connection of audio tracks to the system control means, and the audio track for which the control flag has been detected by the control flag detecting means is determined by the sequence determining means for appropriately outputting information on the connection of audio tracks to the system control means, and the audio track for which the control flag has been detected by the control flag detecting means is determined by the sequence determining means for outputting information on the connection of audio tracks to the system control means, and the audio track for which the control flag has been detected by the control flag detecting means A compressed audio signal playback device that invalidates the audio track number of. (2) The control flag indicating whether it is the last track is
It is determined by the polarity of flags added to the start and end of the compressed audio signal, and the polarity of the flags at the start and end are both positive, and the control flag detection means detects the flag recorded in one track with positive polarity. 2. The compressed audio signal reproducing apparatus according to claim 1, further comprising a correct flag detecting means for detecting the number of correct flags, and a comparing means for inputting the output of the correct flag detecting means and comparing it with a predetermined value.