JPH03248359A - Inter-music detecting system for digital tape recorder - Google Patents

Abstract

PURPOSE:To prevent erroneous detection from occurring by deciding a threshold level from the maximum value or the minimum value of the past level. CONSTITUTION:This system is provided with a level monitoring means 1 which monitors the current level of an audio signal, a maximum level storage means 3 which stores the maximum value of the past level out of levels monitored by the level monitoring means 1, and a minimum level storage means 5 which stores the minimum value of the past level out of the levels monitored by the level monitoring means 1. The threshold level can be decided from the maximum value or the minimum value of the past level. Therefore, the threshold level can be decided corresponding to the level of music. In such a manner, the errone ous detection where the state in the interval of the music is assumed in spite of the continuation of the music or vice versa can be prevented from occurring.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for detecting between songs in a digital tape recorder, and in particular, to a method for detecting intervals between songs in a digital tape recorder, in particular, a method for detecting intervals in which the level of a digitized audio signal remains below a threshold level for a predetermined period of time. This relates to what is detected as an inter-song interval when the above continues.

[Prior Art] In some digital tape recorders, a start ID is written at the beginning of a multi-track record to facilitate cueing.

In order to write this start ID, it is necessary to detect the beginning of a song (that is, between songs).

As shown in FIG. 5, the conventional digital tape recorder's inter-track detection method includes level discrimination means 102. As shown in FIG. This level discrimination means 102 converts the digitized audio signal transmitted to the digital signal line 104 consisting of a plurality of bits into a predetermined level drop (for example, −60 dB) from full scale (for example, 97.2 dB). The level of the audio signal is discriminated based on the threshold level set to .

In such a conventional song interval detection method of a digital tape recorder, the level of the music signal falls below the threshold level as shown in a of FIG. 6(1), and
As shown in (b), if the state of being below the threshold level continues for a predetermined period of time (for example, 2 seconds) or more, it is detected that the time is between songs. After preparing to write the start ID, if the audio signal level exceeds the threshold level as shown in C in Figure 6 (1), that is, the start ID is written on the magnetic tape for 9 seconds at the beginning of the song. Written intentionally.

[Problems to be Solved by the Invention] However, in such conventional technology, the threshold level is determined based on the full scale, that is, it is assumed that the maximum level of the music signal reaches the full scale. Therefore, there were the following problems.

First of all, if the dynamic range of the audio signal is poor, for example when recording is performed using a cassette tape recorder as the source, the minimum value of the audio signal will exceed the threshold level as shown in Figure 6 (2). Sometimes I put it away. In this case, the level discrimination means cannot detect the intervals between songs. Therefore, in this case, the songs are continuous, i.e., there is no interlude, and the star) ID
could not be written.

Second, when the level of the audio signal is reduced, for example, when the audio signal from the source is recorded with the volume reduced, the maximum value of the audio signal will exceed the threshold level as shown in Figure 6 (3). Sometimes it goes below. In this case, the level discrimination means cannot detect the intervals between songs. Therefore, in this case as well, the start ID could not be written.

Thirdly, when the dynamic range of the audio signal is wide and the period of low level of the audio signal continues for a long time, for example, when classical music is recorded, even though it is in the middle of the song, ), the level of the audio signal often falls below the threshold level. Therefore, in this case, the start I frequently occurs while the song continues.
I ended up writing a D.

The present invention solves the above-mentioned technical problems, and reduces the possibility of detecting that the song is between songs even though the song is continuing, and reduces the detection that the song is continuing even though it is between songs. An object of the present invention is to provide a method for detecting intervals between songs in a digital tape recorder.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention has the following configuration.

FIG. 1 shows an overall configuration diagram of a song interval detection method for a digital tape recorder according to the present invention.

The inter-song detection method of this digital tape recorder includes a level monitor means 1 that monitors the current level of the audio signal, and a maximum level memory that stores the maximum value of the past level among the levels monitored by the level monitor means 1. From the maximum value stored in at least one of the minimum level storage means 5 which stores the minimum value of past levels among the levels monitored by the means 3 or the level monitor means 1, and the maximum level storage means 3, A predetermined drop in level, or
The present invention is characterized by comprising a level discrimination means 7 for discriminating the level of the audio signal at a threshold level set to a predetermined level increase from the minimum value stored in the minimum level detection means 5.

[Operation The co-level monitor means 1 monitors the current level of the audio signal. At least one of maximum level storage means 3 and minimum level detection means 5 is provided. The maximum level storage means 3 stores the maximum value of the past level among the levels monitored by the level monitor means 1. The minimum level detecting means 5 stores the minimum value of the past levels among the levels monitored by the level monitoring means 1. Level discrimination means 7
is set to a predetermined level drop from the maximum value stored in the maximum level storage means 3, or a predetermined level increase from the minimum value stored in the minimum level detection means 5. The level of the audio signal is discriminated by the threshold level.

In the present invention, the threshold level is determined from the maximum value of the past level or the minimum value of the past level. Therefore, since the threshold level can be set according to the level of the song, it is possible to reduce the possibility of detecting that the song is between songs even though it is continuing, and detecting that the song is continuing even though it is between songs. Detection can be reduced.

[Example] Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 is a circuit diagram of a digital tape recorder according to an embodiment of the present invention.

The analog audio signal input from the line input 2 is level-adjusted by a recording volume 4, and then passed through a line amplifier 6 and a low-pass filter 8 to an A/D converter 10.
and digitized. The digitized audio signal is input to the digital signal processor 12. Note that the A/D conversion of the A/D converter 10 is performed in both polarities. Further, the digitized audio signal inputted from the digital human power 14 is passed through the line amplifier 16 and the digital input/output circuit 18 to the digital signal processor 12.
is input.

The digital signal processor 12 is a circuit that interleaves digital data, adds an error correction code, etc.
Equipped with F amplifier, servo circuit, etc.

The audio signal input to the digital signal processor 12 is sent to the rotary head 24 via the recording/reproducing amplifier 22 and written on the magnetic tape 26. Note that subcodes are provided before and after the written audio signal to write data such as the song number, start ID, and time. This subcode is written when recording a music signal, and
Written during playback with dubbing.

The audio signal written on the magnetic tape 26 is input to the digital signal processor 12 via the rotary head 24. The audio signal output from the digital signal processor 12 is input to the D/A converter 34 via the digital filter 32 and converted into an analog signal. The analog audio signal is passed through a de-emphasis circuit 36, a low-pass filter 38, a line amplifier 40, and a muting circuit 4.
2 from line output 44. Further, the analog audio signal that has passed through the muting circuit 42 is level-adjusted with a playback volume 46, and is outputted from a headphone output 50 via a line amplifier 48. Further, the audio signal output from the digital signal processor 12 is transmitted to the digital output 5 via the digital input/output circuit 18, the line amplifier 52, and the line transformer 54.
It is output from 6.

A bus 62 is connected to the digital signal processor 12 . This bus 62 includes a CPU 64, a ROM 66,
A RAM 68, a display 70, etc. are connected. The display 70 displays the level of the audio signal input to the digital signal processor 12, etc. The CPU 64 monitors the level of the audio signal input to the digital signal processor 12 in accordance with a song interval detection program stored in the ROM 66, and stores the monitoring results in the RAM 68. As shown in FIG. 3, the RAM 68 includes a storage area (2) for storing the current signal level L of the audio signal, a storage area (2) for storing the past maximum signal level Lmax of the audio signal, and a storage area (2) for storing the past maximum signal level Lmax of the audio signal. Storage area ■ to store the signal level L min, storage area ■ to store the current dynamic range R of the audio signal (R=L-L-1,), past maximum dynamic range Ra a x of the audio signal
Storage area ■ to store (R,,,,=L,,,-L1.) Storage area■ to store threshold level THL
etc. will be provided.

Note that the negative curvature of the audio signal is reversed and the average value over a certain period of time is monitored.

FIG. 4 is a flowchart of the song interval detection program.

First, in step m, initial values are set in the storage areas (2) and (2) as the past maximum signal level L M a 1 and the past minimum signal level L m l n. As this initial value, a predetermined level drop value from the current signal level L or full scale is selected.

Next, in step m2, it is determined whether the current signal level L is 0.8 or more above the past maximum signal level. If it is above, proceed to step m, and the maximum level L
ma. is updated to the current signal level L (storage area ■
). When step ms is completed, the process proceeds to step m8. In step m2, if the current signal level L is less than the past maximum signal level LfflaX, step m
4, it is determined whether the current signal level L is less than or equal to the past minimum signal level L1°. If not, step m1. Proceed to. If below, step m5
Then, the past minimum signal level L, n is updated to the current signal level L (storage area ■). Then step m
Proceeding to step 6, the contents of the storage area (2) are updated to the current dynamic range R (R=LL, +I,) and stored. Next, the process advances to step m7.

In step m7, the current dynamic range R is changed to the past maximum dynamic range Rmat (Rmat”
L tax L ml. ) or more.

If not, proceed to step m, 3. If it is above, proceed to step ms. In step m8, the storage area ■
The stored contents are updated to the current dynamic range R as the past maximum dynamic range R□.

Next, the process proceeds to step m9, where it is determined whether the current level L is less than the threshold level THL. If it is equal to or higher than the threshold level T)IL, step m1. Proceed to. If it is less than the threshold level THL, the process proceeds to step m1° and a timer count is started. Next, step m! , and set the threshold level THL.
It is determined whether or not the time T, which is less than 2 seconds, has passed. If 2 seconds have not elapsed, it is assumed that the song has not ended, and the process proceeds to step m□3.

If 2 seconds have elapsed, it is assumed that the song has ended, and the process proceeds to step m12, where preparations are made to write the start ID.

Next, in step mI2, it is determined whether the start ID is ready to be written. If writing is not ready, return to step m2. If the write preparation is complete, the process proceeds to step m14, where it is determined whether or not the current signal level L exceeds the threshold level T)IL.
That is, it is determined whether the song has started. If the threshold level T)IL is not exceeded, step m1
Return to 3 and repeat until exceeded. If it exceeds the threshold level TML, it is considered to be the beginning of the song, and step m
Proceed to step 15, write the start ID for 9 seconds, complete the process, and return to the start.

In this way, the song interval is detected and the start ID is automatically written on the magnetic tape for 9 seconds.

In addition, in the above-mentioned embodiment, the past maximum signal level L3
．． 8 and the past minimum signal level L m l n are stored, and the threshold level is set to a predetermined level drop from the past maximum signal level L, . As another embodiment, the past maximum signal level L,...8 is stored and the threshold level is set to a predetermined level drop from the past maximum signal level L,...A. Alternatively, the past minimum signal level L m l n may be stored, and the threshold level may be set to a predetermined level increase from the past minimum signal level L m l n. You can also do this.

Further, the level monitor means, maximum level storage means, minimum level detection means, and level discrimination means are implemented by the CPU.

Although it is configured using ROMSRAM, it may also be configured using a logic circuit or the like.

[Effects of the Invention] As described above, in the present invention, the threshold level is determined from the maximum value of the past level or the minimum value of the past level.

Therefore, since the threshold level can be set according to the level of the song, it is possible to reduce the possibility of detecting that the song is between songs even though it is continuing, and detecting that the song is continuing even though it is between songs. Detection can be reduced.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the inter-track detection method of a digital tape recorder according to the present invention, Fig. 2 is a circuit diagram of a digital tape recorder according to an embodiment of the present invention, Fig. 3 is a memory map of the RAM 68, and Fig. 4 is a diagram. FIG. 5 is a flowchart of the song interval detection program, FIG. 5 is an overall configuration diagram of the song interval detection method of a conventional digital tape recorder, and FIG. 6 is a diagram for explaining the operation of FIG. 5. 1...Level monitor means 3...Maximum level storage means 5...Minimum level detection means 7...Level discrimination means 6 Fig. 2 seconds

Claims (1)

[Claims] In a song interval detection method for a digital tape recorder that detects a song interval when the level of a digitized audio signal continues to be lower than a threshold level for a predetermined time or more, a level monitor means for monitoring the current level; and a maximum level storage means for storing the maximum value of past levels among the levels monitored by the level monitor means;
At least one of minimum level storage means for storing the minimum value of past levels among the levels monitored by the level monitor means; and a predetermined level drop from the maximum value stored in the maximum level storage means; , a level discrimination means for discriminating the level of an audio signal at a threshold level set to a predetermined level increase from the minimum value stored in the minimum level detection means. Recorder's song interval detection method.