DE9117085U1 - Device for reproducing audio signals - Google Patents

Description

Device for playing audio signals

The invention relates to a device for reproducing audio signals according to the preamble of claim 1 or according to the preamble of claim 6.

The audio signals are recorded on a video magnetic disk. In this type of video magnetic disk, each of the tracks on which the audio signals are recorded is usually divided into four sectors. The head or beginning of the audio signals is made by demodulating the audio signals recorded in the sector at the top of the track, as described in Japanese Patent Application Laid-Open No. 1-269292, and the signals are output one after another as one voice.

Audio signals can be recorded and played back in modes of about 5 seconds, about 10 seconds or about 20 seconds per track.

reproduced according to the compression ratio. Since each track consists of four sectors as described above, the recording and playback time per sector in each mode is accordingly approximately 1.2 seconds, approximately 2.5 seconds and approximately 5 seconds, respectively.

However, if, for example, the voices are recorded in the mode of about 5 seconds per track, the playback time is about 1.2 seconds, i.e. very short. Therefore, it is difficult to recognize the voices being played back. It becomes difficult to recover a designated track. On the other hand, if all the audio signals are recovered, it takes a long time and the recovery efficiency deteriorates.

JP-2-98852 (A) describes a device for reproducing audio signals in which the audio signals are recorded with a fixed recording mode. As a result, the known device cannot be used flexibly.

DE 3 9 3 4 631 A1 describes a device for reproducing audio signals recorded on a recording medium. The known device works with a fixed recording mode for the audio signals. In order to recognize the contents of the sound pieces recorded on the recording medium, the audio signals are reproduced within a predetermined time with a stretching ratio that is smaller than that used for natural reproduction of the audio signals.

It is the object of the invention to provide a device for reproducing audio signals which, in the case of recordings with different compression levels, reproduces sufficient information content when the pieces are briefly played.

This object is achieved by the features of patent claims 1 and 6. Advantageous further developments are specified in the subclaims.

Further features and advantages of the invention emerge from the following description, which, in conjunction with the accompanying drawings, explains the invention using exemplary embodiments. They show:

Fig. 1 is a block diagram of a disk recording/reproducing apparatus to which an audio signal reproducing apparatus and method according to the present invention are applied;

Fig. 2 is a schematic view of a video storage disk;

Fig. 3 is an illustration of the relationship between a track and sectors of a video storage disk;

Fig. 4 is a schematic representation of the recording state of an audio signal;

Fig. 5 is a flow chart illustrating a first method for recovering audio signals;

Fig. 6 is a flow chart illustrating a second method for recovering audio signals;

Fig. 7 is a flow chart showing a

third method for recovering audio signals;

Fig. 8 is a flow chart showing a

fourth method for recovering audio signals;

Fig. 9 is a flow chart showing a

fifth method for recovering audio signals;

Fig. 10 is a flow chart showing a

sixth method for recovering audio signals and

Fig. 11 is a flow chart showing a

seventh method for recovering audio signals.

The present invention will now be explained with reference to the embodiments shown in the drawings.

Figure 1 shows a circuit diagram of a recording/playback device operating with a storage disk, in which the inventive solution for recovering audio signals is found. A system control unit 11 is formed by a microcomputer known per se, which controls the entire arrangement. An actuating device 12 carries out various operations. An audio recovery button 13, a stop button 14 and a

High speed playback button 19, etc. are connected to the system control unit 11. Furthermore, a display device 15 for displaying various status displays is connected to the system control unit 11.

A disk drive unit includes a magnetic head 21, a tracking circuit 22 for controlling the magnetic head 21, a spindle motor 23 for rotating a video disk (floppy disk) D, a servo circuit 24 for driving and controlling the motor 23, and a PG (pulse generator) coil 25 for detecting a rotational speed of the video disk D. The PG coil 25 is connected to the servo circuit 24. The servo circuit 24 and the tracking circuit 22 are connected to the system control unit 11, which controls the magnetic disk drive so that the magnetic disk D rotates at a speed of 3,600 revolutions per minute.

A video image recording/reproducing circuit 16 is controlled by the system control unit 11 to separate video signals input from a video camera or the like (not shown) into color difference signals and brightness signals and to frequency modulate them by means of a switch 17 and record them on a video disk D. The video image recording/reproducing circuit 16 is further connected to a video output terminal (not shown). By connecting a playback device (not shown) to this terminal, it is therefore possible to view the video images recorded on the video disk D. The switch 17 is controlled by the system control unit 11 in such a way that it is connected to the video recording/reproducing circuit side.

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circuit 16 is closed when video images are recorded and reproduced, and that it is closed on the audio playback and recording circuit 31 side (which will be described later) when voices are recorded and reproduced.

A circuit arrangement for recording and reproducing voices is described below.

The audio recording and reproducing circuit 31 performs frequency modulation and frequency demodulation of signals. It is connected to the magnetic head 21 through the switch 17. An emphasis circuit 32 emphasises the high frequency component of audio signals transmitted from an audio memory when voices are recorded on the disk D and outputs the same to the audio recording and reproducing circuit 31. The emphasis circuit 32 is connected to the audio memory 33 through a low pass filter 34 and a digital/analog converter 35. An equalization circuit 36 suppresses the high frequency component of the audio signals output from the audio recording/reproducing circuit 31 when the voices recorded on the disk D are reproduced. The equalization circuit 3 6 is connected to the audio memory 3 3 via a low-pass filter 3 7 and an analog/digital converter 38.

A microphone 31 is connected to a switch 45 via an amplifier 42. A loudspeaker 43 is also connected to the switch 45 via another amplifier 44. The switch 45 is controlled by the system control unit 11 so that it is on the

side of the microphone amplifier 42 is closed when voices are recorded and on the side of the loudspeaker amplifier 44 is closed when voices are reproduced. The switch 45 is connected to a noise reduction circuit 46 which is connected to a low-pass filter 47. This is connected to an analog-digital converter 51 and a digital-analog converter 52 via a switch 58. The analog-digital converter 51 and the digital-analog converter

52 are connected to the audio memory 33. The switch 48 is controlled by the system control unit 11 in such a way that it is closed on the analog-to-digital converter 51 side when voices are recorded and that it is closed on the digital-to-analog converter 52 side when voices are reproduced. It is to be noted that the noise reduction circuit 46 and the low-pass filter 47 are controlled by the system control unit 11.

A timing unit 53 is connected to the audio memory 33, the analog-digital converters 51, 38 and the digital-analog converters 52, 35. The timing unit

53 is controlled by the system control unit 11 in such a way that audio signals are compressed and expanded in the time axis in conjunction with the audio memory 33, the analog-digital converters 51, 38 and digital-analog converters 52, 35 when voices are recorded on or reproduced from the disk D.

When voices are recorded, these voices picked up by the microphone 41 pass through the amplifier 42, the noise reduction circuit 46 and the low-pass filter 47, after which they are fed to the analog-digital converter 51. The audio signals are then time-compressed by the action of the analog-digital converter.

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converter 51, the audio memory 3 3 and the timing circuit 53. After their conversion in the digital/analog converter, they pass through the low-pass filter 34, whereupon their high frequency component is boosted by the boosting circuit 3 2. The audio signals are then frequency modulated by the audio recording/playback circuit 31 and recorded on the disk D.

When voices are reproduced, the audio signals recorded on the disk D are frequency modulated by the audio recording/reproducing circuit 31. Then, the high frequency component of the audio signals is suppressed by the equalizing circuit. Then, the audio signals pass through the low-pass filter 37 and the analog-digital converter 38 and are stored in the audio memory 33. The signals stored in the audio memory 33 are time-expanded by the action of the audio memory 33, the timing circuit 53 and the digital-analog converter 52. At the same time, they are output as analog signals and pass through the low-pass filter 47, the noise reduction circuit 46 and the amplifier 44, whereupon they are reproduced by the speaker 43.

The audio signals are time-compressed to be recorded on the magnetic disk D rotating at 3,600 revolutions. When voices are reproduced, the audio signals are stretched in time with a stretching ratio that corresponds to the compression ratio mentioned above.

Figure 2 shows a video magnetic disk D used in the disk recording/reproducing apparatus shown in Figure 1. The video disk D (floppy disk) is, for example, a 2-inch magnetic disk. The first through the fiftieth tracks, counted from the outside of the disk D, are used for recording video images, voices, and the like. Nothing is recorded on the fifty-first track. The fifty-second track is a wait track on which wait signals are recorded. Note that a track on which audio signals are recorded is divided into four sectors.

Figure 3 shows a relationship between the tracks and sectors on the video disk D. In the embodiment shown in Figure 3, the video image signals are recorded on the sixth, seventh, ninth, tenth and twelfth tracks. Audio signals are recorded on the fifth, eighth, eleventh and thirteenth tracks. Video image signals are recorded on a track as a unit. On the other hand, the track on which audio signals are recorded is divided into four sectors and the audio signals are recorded in such a way that one sector forms a unit. As will be described later, a series of audio signals can be formed by connecting the various sectors together.

There are four types of recording patterns for signals in the sectors in which audio signals are recorded. Type 1 (1 in the circle in Figure 3) is a sector followed by a sector in which audio signals are recorded; Type 2 (2 in the circle in Figure 3) is a sector containing audio signals followed by other sectors in

audio signals recorded in another sector follow; type 3 (3 in circle in Figure 3) is a sector in which a series of audio signals ends; and type 4 (4 in circle in Figure 3) is a sector in which no audio signal is recorded. In the example shown in Figure 3, namely, audio signals continue continuously from sector 2 of the fifth track to the eighth track, from sector 3 of the eighth track to the eleventh track, and from sector 1 of the eleventh track to sector 0 of the thirteenth track, where the signals end. A series of audio signals is recorded over the predetermined tracks of the fifth, eighth, eleventh and thirteenth tracks.

Figure 4 schematically shows a recording state of a signal in a sector in which audio signals are recorded. As shown in the figure, a signal starting from the start flag Fl and ending from the end flag F2 is recorded in each of the sectors. A control code Cl for recording various data is recorded immediately after the start flag Fl. Audio wave signals C2 are recorded between the control code Cl and the end flag F2.

In the type 1 of the signal recording patterns shown in Figure 4, the start flag Fl is a high level signal and the end flag F2 is a low level signal. Although in the type 2 pattern the start flag Fl is a high level signal and the end flag F2 is a low level signal, a sector following the type 2 sector in the same track is not a type 3 pattern. In the type 3 pattern, both the start flag and the end flag F2 are low level signals. In the type 4 pattern, the start flag Fl is a low level signal and the end flag is a high level signal.

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Figure 5 is a flow chart for explaining a first method for recovering audio signals. This routine is started by pressing the audio recovery key 13 in Figure 1.

In step 101 in Fig. 5, it is determined whether or not the magnetic head 21 is positioned over the fiftieth track of the video disk D, i.e., the innermost track of the recording tracks. The video disk D is read from the outer peripheral edge toward the center of the disk. If the magnetic head 21 is positioned over the fiftieth track because the reading of the recording tracks is completed, a timer (not shown) is stopped in step 119, and the process is terminated.

If the reproduction of the fiftieth track has not been carried out, a track search and setting operation is carried out in step 102, whereby the magnetic head 21 is moved inward by one track. Next, in step 103, it is determined whether the track to be reproduced is a track on which audio signals are recorded or not. This is determined from the number of an output signal received from a sync signal separating circuit (not shown). Since the sync signal separating circuit detects the start flag Fl and the end flag F2 as a vertical sync signal when audio signals are stored on the track currently being reproduced, the number of sync signals is larger than that of a track on which image signals are recorded.

If no audio signals are recorded on the track, the process returns to step 101. On the other hand, if audio signals are recorded on the track, it is determined in step 104 by reading the control code Cl (Figure 4) whether or not this sector is the header of a series of audio signals. The track number and the sector number of a header sector are namely recorded in the control code Cl in each sector of a series of audio signals. By reading these numbers, it is determined whether or not this sector is the header of a series of audio signals. If the track now being played back is not the header of a series of audio signals, the process returns to step 101. On the other hand, if the track is the header of a series of audio signals, step 105 and the following steps are carried out.

In step 105, a time limit is set in the timer * . In step 106, the timer is started.

Subsequently, in step 111*, a reproduction of audio signals is started. In step 112, it is determined whether the stop button 14 (Figure 1) has been pressed or not. If the stop button 14 has been pressed, the timer is stopped in step 119 and the process is forcibly terminated in this case. If, on the other hand, the stop button has not been pressed, step 113 and the following steps are carried out. In step 113, it is namely determined whether the sector now being reproduced is a type 3 pattern or not, i.e. whether the sector is the end of a series of audio signals. If the sector is not a type 3 pattern, the timer started in step 106 is checked in step 114. It is determined whether the time has elapsed or not. It is namely determined whether the time set in step

105 has been exceeded or not. If the time limit has not yet been exceeded, it is determined in step 115 whether the sector now being played is a type 2 pattern in which the audio signals are followed by a sector from another track. If it is not a type 2 pattern, the process returns directly to step 111. If the sector is a type 2 pattern, the magnetic head is reset in step

116 is set to the following track and the process returns to step 111.

Steps 111 to 116 are repeatedly executed, so that audio signals are reproduced in some sectors. If it is determined in step 113 that the sector now being reproduced is a Type 3 pattern or if it is determined in step 114 that the set time has elapsed, the reproduction of the audio signals is then stopped in step

117. At the same time, the timer is stopped in step 118. The method returns to step 101. The method sequence described so far is repeatedly executed, whereby the next series of audio signals is reproduced, i.e. a header of the next series of audio signals is executed.

As described above, in the first method, audio signals are reproduced in a predetermined time regardless of the compression ratio when recording the audio signals. As a result, even if it is a mode in which voices are recorded for about 5 seconds per track, the reproduction time is, for example, 2.5 seconds. (In this embodiment, the predetermined time is set to 2.5 seconds.) Therefore, the reproduction time

sufficient to enable recognition of the contents of the voices. It is also easier to retrieve the information on a specific track. Furthermore, in the first method, even if audio signals with different recording modes are mixed and present on a video recording disk, a specific selected track can be accurately retrieved because the audio signals can be reproduced in a fixed time.

Figure 6 is a flow chart for explaining a second method for recovering audio signals. This routine is started by depressing button 13 in Figure 1.

Since the operations in steps 201, 202, 203 and 204 of Figure 6 are the same as steps 101 to 104 in Figure 5, the description of these operations will not be repeated.

In step 205, a reference value N, which indicates the number of sectors to be reproduced, is set to "1". This is of course only an example and the reference number N could be set to "2" or a larger number if necessary. In step 206, it is determined whether audio signals have been recorded in a first mode in which voices are recorded for about 20 seconds per track. If the mode is not the first mode, it is determined in step 207 whether the audio signals are recorded in a second mode in which voices are recorded for about 10 seconds per track. If the mode is determined to be the second mode, the reference value N is set to

?, 1.5 -

If it is determined that it is not the second mode but a third mode in which voices are recorded for about 5 seconds per track, the reference value N is changed to "4N" in step 208.

Then, in step 210, a counter M is set to the value "1". The voices are reproduced in step 211 and in the following steps.

In step 211, a sector is reproduced, causing the voices to be reproduced. Then, in step 212, it is determined whether or not the stop button 14 (Fig. 1) has been pressed. If the stop button 14 has been pressed, in this case the process is forcibly terminated. On the other hand, if the stop button has not been pressed, step 213 and the following steps are carried out. First, in step 213, it is determined whether or not the sector being reproduced is a type 3 pattern, i.e. whether the sector is the end of a series of audio signals. If the sector is a type 3 pattern, the process immediately returns to step 201, since the series of audio signals is thus terminated. On the other hand, if the "sector" is not a type 3 pattern, it is determined in step 214 whether or not the counter M has reached the reference value N. When the counter M has reached the reference value N, i.e. when a predetermined number of sectors have been reproduced, the method returns to step 201 and the header of a next audio signal is started.

On the other hand, if a predetermined number of sectors have not been reproduced and the counter M has not yet reached the reference value N, the counter M is incremented by the value "1" in step 215. Then, in step 216, it is determined whether or not the sector being reproduced is a type 2 pattern, i.e., whether or not the audio signals recorded in the sector are continued on a sector of another track. If the sector being reproduced is not a type 2 pattern, the process returns directly to step 211. On the other hand, if it is a type 2 pattern, the magnetic head 21 is moved to a following track in step 217 and the process returns to step 211.

Steps 211 to 217 are repeatedly executed, thereby reproducing audio signals recorded in a predetermined number of sectors. If it is determined in step 213 that the sector being reproduced is a Type 3 pattern, or if it is determined in step 214 that a predetermined number of sectors have been reproduced, the process returns to step 201. The above-described operations are repeatedly executed, thereby reproducing another series of audio signals.

As described above, in the second method of reproducing signals, the amount of reproduction (or the number of sectors to be reproduced) is changed according to the compression ratio when recording audio signals. The smaller the compression ratio, the larger the number of sectors reproduced for the header. Namely, the reproduction time is constant (5

seconds) regardless of the recording mode of the audio signals. Therefore, even if the mode is one in which voices are recorded for about 5 seconds per track and the compression ratio is low, the playback time is sufficiently extended so that the voices can be easily recognized. Therefore, it is possible to accurately reproduce a selected track. Furthermore, with this method, even if audio signals having different recording modes are mixed and exist on a video disk, the number of sectors corresponding to each of the modes is reproduced. In this way, it is possible to accurately reproduce the information existing on a selected track.

Figure 7 shows a flow chart for explaining a third method for recovering audio signals. This routine is started by pressing the audio recovery key 13 (Figure 1).

In step 3 01, a readout clock is set to a high-speed mode. This readout clock is a pulse signal that is sent out at predetermined intervals so as to time the readout when audio signals recorded on the video storage disk are reproduced. The clock signal is generated by a clock generator routine (not shown). The generator cycle of the pulse signal is made short by executing step 3 01.

In step 302, it is determined whether the track currently being played back is one on which audio signals are recorded. This is determined based on

signals output by a synchronous signal separating circuit (not shown). If audio signals are recorded on the track, it is determined whether this is the head of a series of audio signals by reading a control code Cl (Figure 4) in step 303, as in step 104 in Figure 5.

When the head part of a series of audio signals is to be reproduced, step 304 is executed and the audio signals are reproduced at high speed according to the readout clock set to the high speed mode in step 301. Namely, in this method, audio signals of a series of signals starting with type 1 patterns and ending with type 3 patterns (in Figure 3, the audio signals starting from sector 0 of track 5 and ending from sector 0 of track 13) are all reproduced. The speed of reproduction is faster than, for example, twice the conventional reproduction speed. In other words, the stretch ratio of the audio signals in this reproduction is lower than the stretch ratio in conventional reproduction. If 5 seconds of audio signals are recorded in the mode in which voices are recorded for about 5 seconds per track, all the audio signals are reproduced in about 2.5 seconds.

When the high-speed reproduction is completed, it is determined in step 205 whether the stop button 14 has been pressed or not. If the stop button 14 has been pressed, the readout clock is set to a conventional speed mode, i.e. a conventional reproduction state, in step 306 and the process is terminated.

On the other hand, if it is determined in step 305 that the stop key has not been pressed, it is determined in step 307 whether or not the track being reproduced now corresponds to the fiftieth track of the video storage disk, i.e. the innermost track of the recording tracks. The video storage disk D is read from the outer edge to the center. If the reproduction of the fiftieth track is completed, the readout clock is then set to the usual speed mode in step 306 and the process is terminated. On the other hand, if the reproduction of the fiftieth track is not completed, a track search and setting operation is carried out in step 308 and the magnetic head 21 is moved inward by one track. The process then returns to step 302.

If it is determined in step 302 that the track to be reproduced is not a track on which audio signals are recorded, or if it is determined in step 303 that the sector read is not a header of a series of audio signals, steps 307 and the following steps are executed. Namely, if the reproduction of the fiftieth track is completed, the readout clock is set to the conventional speed and the process is terminated. On the other hand, if the reproduction of the fiftieth track is not yet completed, a track located within the fiftieth track is reproduced.

As described above, according to the third signal retrieval method, since all series of audio signals are reproduced at high speed in retrieving the audio signals, all voices can be heard in a short time, so that the retrieval time is shortened and the efficiency of retrieval is greatly increased.

Figure 8 shows a flow chart for explaining a fourth method for recovering audio signals. This routine is started by depressing the button 13 (in Figure 1).

Since steps 401 to 406 of Figure 8 are equivalent to steps 101 to 106 in Figure 5 and steps 411 to 419 are the same as steps 111 to 119 in Figure 5, a description of these steps will not be repeated.

If it is determined in step 401 that the magnetic head 21 is on the fiftieth track, the timer is stopped in step 419 and the readout clock is set to the usual speed in step 420. Then the process is terminated. It should be noted that the timer is stopped in order to prevent termination of the process in a state in which the timer is operated due to step 406 to be explained later.

Although steps 411 to 416 are repeatedly executed to reproduce audio signals in some sectors, if it is determined in step 413 that the sector to be reproduced is a Type 3 pattern, or if it is determined in step 414 that a predetermined time has elapsed, the reproduction of the audio signals is stopped in step 417 and the timer 418 is stopped.

Then, in step 421, the method waits for a predetermined fixed time (for example, 3 seconds) and it is determined in step 422 whether the high-speed playback button 19 (Figure 1)

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has been pressed or not. The high-speed playback button 19 is pressed when details of the audio signals are not clearly understood during playback of the audio signals in steps 411 to 416. Therefore, it is necessary to reproduce the same audio signals at high speed. Therefore, when the high-speed playback button 19 is pressed during the waiting time in step 421, step 423 and the following steps are executed to perform the high-speed playback. On the other hand, when the high-speed playback button 19 has not been pressed during the waiting time, the process returns to step 401.

In step 423, the magnetic head 21 returns to the head section of a series of audio signals. This head sector is the same as that detected in step 404, so that the same audio signals as in steps 411 to 416 are reproduced again.

In step 424, the readout clock is set to the high speed mode as in step 301 in the third method described with reference to Figure 7. Then, in step 425, all audio signals from a series thereof are reproduced at a higher speed than the usual playback speed. In step 426, the readout clock is reset to the usual speed mode. In step 427, it is determined whether or not the stop button 14 has been pressed. If it has been pressed, the method is immediately terminated. If it has not been pressed, the method returns to step 401 and each of the operations described above is repeated so that the following audio signals are also reproduced.

As described above, in the fourth signal retrieval method, when the same audio signals need to be reproduced again during retrieval of audio signals in which the audio signals are reproduced at a usual speed, the second reproduction is performed at a high speed. Namely, in the second reproduction, the audio signals are reproduced at a smaller stretch ratio than the stretch ratio during the first reproduction. Therefore, even if it is difficult to reproduce the audio signals because the time limit of the timer set in step 405 is too short, for example, all the audio signals are reproduced and their retrieval is carried out securely. Furthermore, since all the audio signals are reproduced at a high speed, their retrieval is carried out with a high efficiency in a short time.

Figure 9 shows a flow chart of a fifth method for recovering audio signals. This routine is started by depressing the button 13 (Figure 1) as in the fourth recovery method described with reference to Figure 8.

Steps 501 to 506 of Figure 9 are equivalent to steps 401 to 406 in Figure 8. Steps 511 to 514 of the flow chart shown in Figure 9 are equivalent to steps 411 to 414 of Figure 8, so that a description of these steps is unnecessary.

When the high-speed playback key 19 is depressed in this process to reproduce audio signals, the readout clock is

If the high speed mode is set in step 524, then in step 525 the time limit aT of the timer is set to the time limit T set in step 505. Where a denotes a constant that satisfies the following condition:

a > (Fn/Ff)

in it, the usual clock frequency is designated as Fn and the high-speed clock frequency as Ff. For example, if Fn/Ff = 1/2, the value "1" or "2" can be selected for a. The time period aT is then of such a length that even if all voices cannot be reproduced within the time period aT when reproducing a series of audio signals at high speed, more audio signals are reproduced than during usual reproduction within the time T. It should be noted that if a is selected to be a large number, all audio signals can be reproduced.

The process proceeds to step 506. The timer is started to cause steps 511 to 516 to be repeatedly executed, with a series of audio signals being reproduced at high speed.

During high speed reproduction, if it is determined in step 513 that a sector with a Type 3 pattern is being read or if it is determined in step 514 that the predetermined time has elapsed, the process goes to step 517 and the reproduction of the voices is stopped. The timer is then stopped in step 518. After the

After the processing has waited for a certain period of time in step 522, it is then determined in step 522 whether or not the high-speed playback key 19 has been pressed again. If the key 19 has been pressed, the processing returns to step 523 and the high-speed playback is again carried out. On the other hand, if the key 19 has not been pressed, the processing returns to step 501.

As described above, in the fifth method, all audio signals in a row are not reproduced as in the method of Figure 8. Rather, only a part of the audio signals are reproduced. Therefore, the audio signals can be confirmed in a shorter time than in the fourth retrieval method of Figure 8, so that the fifth retrieval method can bring about a further increase in the retrieval efficiency as compared with the fourth method. Note that in a mode in which the voices are recorded for, for example, 5 seconds per track, all audio signals can be reproduced.

Figure 10 shows a flow chart to explain a sixth signal recovery method for recovering audio signals. This routine is started by pressing the button 13 (Figure 1).

The operations in steps 601 to 610 of Figure 10 are the same as in steps 201 to 210 of Figure 6. Therefore, these steps will not be described again.

In step 611, when a sector is being played back, the voices are reproduced. Then, in sector 611, it is determined whether or not the stop key 14 has been pressed. If the key 14 has been pressed, in step 618 the reading clock is set to the usual speed mode, as in step 520 of Figure 9, and the process is terminated. On the other hand, if the key 14 has not been pressed, step 613 is executed. In fact, it is determined whether the sector just read has a type 3 pattern, i.e. whether or not the end of a series of audio signals is contained in it. If it is not a type 3 pattern, in step 614 it is determined whether the counter M has reached the reference value N. If the counter N has not reached the reference value N, step 615 is executed and the counter M is incremented by the value "1". Then, in step 616, it is determined whether the sector being read is a type 2 pattern, i.e., whether the audio signals continue in a sector of another track. If it is not a type 2 pattern, the process returns to step 611. On the other hand, if the sector is a type 2 pattern, the magnetic head 21 is set to the following track by a track search and setting operation in step 617 and the process returns to step 611.

Steps 611 to 617 are repeatedly executed to reproduce the audio signals in a predetermined number of sectors. If it is determined in step 613 that the sector just read is a Type 3 pattern or if it is determined in step 614 that reproduction of a predetermined number of sectors has been completed, steps 621 and the following steps are executed and high-speed reproduction is carried out if necessary.

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Steps 621 to 627 are equivalent to steps 421 to 427 of Figure 8 and are therefore not described in more detail.

As described above, in the sixth signal retrieval method, the reproduction amount of the audio signals can be changed according to the compression ratio used in recording the audio signals. Therefore, the smaller the compression ratio, the larger the number of sectors to be reproduced for the header portion.

Furthermore, when the audio signals are reproduced at high speed, all the audio signals in a row are reproduced. Therefore, even if voices are recorded in a mode with a low compression ratio, the playback time at a high speed is sufficient, so that it is easy to recognize the voices.

Figure 11 shows a flow chart for explaining a seventh method for carrying out the recovery of audio signals. This routine is triggered by pressing the button 13 (Figure 1).

The operations in steps 701 to 718 of Figure 11 are equivalent to those in steps 601 to 618 of Figure 10. Therefore, a description of these operations can be omitted.

If it is determined in step 713 that the sector being reproduced is a type 3 pattern or if it is determined in step 714 that the reproduction of a predetermined number of sectors has been completed, the readout clock is set to

set to the usual speed mode. Steps 721 and the following steps are then carried out, with high speed playback if necessary.

In steps 721 to 724, operations corresponding to those of steps 621 to 624 in Figure 10 are performed. Then, in step 725, the reference value N indicating the number of sectors to be reproduced is set to twice the value set at that time. Then, the process returns to step 710, where the counter M is set to "1". Then, steps 711 and the following steps are performed, whereby the audio signals are reproduced again.

In this case, since the reading clock is set to a high-speed mode in step 724, the audio signals are reproduced at high speed. Furthermore, since the reference value N is doubled in step 725, it is possible to reproduce twice as many sectors as in the initial reproduction.

In the seventh reproducing method, the entire series of audio signals is not reproduced as in the sixth method shown in Fig. 10, but only a part of the audio signals is reproduced at high speed. Therefore, it is possible to confirm the audio signals in a shorter time than in the sixth method shown in Fig. 10. For this reason, the recovery efficiency is increased as compared with the sixth method.

It should be noted that in some modes all audio signals can be reproduced. For example, in the second mode, in which voices are recorded for approximately 10 seconds per track, the number of sectors (2) corresponding to 5 seconds of audio signals is set in step 708 and the number of sectors (4) is set in step 725. Therefore, all audio signals are reproduced.

In the above, a video floppy disk was used as the recording medium for carrying out the described methods. However, the present invention is not limited to the use of such a storage disk. The device according to the invention can also use a magnetic tape or a magnetic drum, etc. as the recording medium.

Claims (8)

Protection claims 1. Device for reproducing audio signals recorded on a recording medium with a predetermined compression ratio corresponding to a certain recording mode, with a detector device for reading out the audio signals, a head detector device for detecting a head part of a series of audio signals, and with a playback device for reproducing the audio signals starting from the head part, wherein a set of audio signals is reproduced within a time period which serves to recognize a recorded piece, characterized in that a device is provided for determining the recording mode of the audio signals read out by the detector device (21), and that the number N of sectors is set according to the set of audio signals to be reproduced depending on the compression ratio such that the number N of sectors of the audio signals to be reproduced is greater the smaller the compression ratio. 2. Device according to claim 1, characterized in that the reproduction device reproduces the audio signals with a first stretching ratio and optionally with a second stretching ratio which is smaller than the first stretching ratio. 3. Device according to claim 2, characterized in that the reproduction device reproduces all audio signals of a series with the second expansion ratio. 4. Device according to claim 2, characterized in that the reproduction device reproduces only a part of a series of audio signals with the second expansion ratio. 5. Device according to claim 4, characterized in that the quantity of audio signals reproduced by the reproduction device is greater than the quantity of audio signals reproduced with the first expansion ratio. 6. Device for reproducing audio signals recorded on a recording medium, with a detector device for reading out the audio signals, a head detector device for detecting a head part of a series of audio signals, and with a playback device for reproducing the audio signals starting from the head part, wherein a set of audio signals is reproduced with a second expansion ratio which is smaller than a first expansion ratio used in a natural reproduction of the audio signals, characterized by a device (53) for setting a recording mode for the audio signals and by a device for determining the recording mode of the audio signals read out by the detector device (21), wherein the audio signals are recorded on the recording medium (23) with a compression ratio depending on the recording mode used, and that the playback device reproduces the audio signals with the first and then with the second expansion ratio. 7. Device according to claim 6, characterized in that the playback device reproduces all audio signals of a series with the second expansion ratio. 8. Device according to claim 6, characterized in that the reproduction device reproduces only a part of a series of audio signals with the second expansion ratio.