JPH0359514B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention provides a compact disc player (hereinafter abbreviated as a "CD player") that plays a digital audio disc called a compact disc, in which the interval between songs during playback is preset. This relates to a method of making the time approximately constant.

Technical Background Compact discs are optical digital audio discs, and information is recorded on one side of a transparent disc with a diameter of 12 cm using digital signals based on the presence or absence of pits from the inner circumference to the outer circumference.
The player reads and reproduces the information using a laser beam.

This compact disk system is a traditional
Compared to LP records, it is possible to record long periods of music on an extremely small disk, and it has excellent characteristics such as dramatically improved sound quality and SN, and no wear on the disk or pickup. Therefore, rapid spread is expected in the future.

By the way, as shown in Fig. 1, the information recording area of this compact disc is configured from the inner circumferential side to the outer circumferential side in the order of a lead-in area, a program area, and a lead-out area. As shown, audio signals such as music are recorded divided into a plurality of songs or movements (in this specification, these are collectively referred to as "songs").

Furthermore, subcode signals as control signals are recorded in two channels, P and Q, over the entire area of the information recording area.

The P channel signal (referred to as P signal) is a signal indicating between songs, and is always "H" between songs, its length is 2 to 3 seconds, and becomes "L" at the beginning of the song.

The Q channel signal (referred to as EQ signal) has "MNR" indicating the song number (music number),
Between songs, it is "00", during a song, it is "X" which indicates the index number to search for changes in lyrics, etc. During a song, it is the time from the beginning of the song, and between songs, it is the time until the next song begins. "time" indicating the time of
and "ATIME" indicating the cumulative time from the start reference point.

Using these subcode signals, the CD player can directly search for a specified song number or randomly search (programmed song selection) in the order of pre-programmed song numbers and play them back.

By the way, the intervals between songs in the program area are
The standard playback time is 2 seconds, but
It is allowed to be longer or shorter than that, and in some cases there is no clear gap between songs, as in music 3 and 4 in Figure 1.

Furthermore, the audio signal recording areas shown by music1 and music2 in Figure 1 are not completely recorded with audio signals from beginning to end; The time until the actual audio signal is output is 0 to 1.5
seconds, and after the audio signal disappeared
The time it takes for the MNR to change and the P signal to fall is about 1 to 10 seconds, and it varies considerably depending on the disc and even the song being recorded.

Therefore, even when playing the songs recorded on a disk in order, the lengths between songs may vary and feel unnatural to the listener, and the gaps between songs may be too long or too short. many.

Furthermore, in the case of program song selection, the search time is extremely short (about 1 second or less), so there may be almost no gaps between songs.

Purpose This invention was made in order to solve such problems, and even when playing songs recorded on a compact disc in order in a CD player, it is possible to perform a random search using program selection, etc. It is an object of the present invention to make it possible for the time between songs to be a substantially constant time set in advance even when the songs are played back.

Configuration Therefore, the present invention determines that a song has ended when the audio signal played from a compact disc falls below a preset level in a CD player, and starts measuring a preset time.
After that, the beginning of the next song to be played is detected using the subcode, but if the beginning of the next song to be played is detected before the measurement of the set time is finished, the measurement of the set time is finished. If the start of playback is delayed by waiting until the start of the next song is detected, and the set time measurement ends before the beginning of the next song to be played is detected, the program immediately fast-forwards to detect the beginning of the next song to be played and starts playback. This provides a method for making the time between songs constant by starting the song.

Embodiment FIG. 2 is a block circuit diagram showing only the main parts of a CD player embodying the present invention.

The audio signal read out from the compact disk by an optical pickup (not shown) is
After undergoing predetermined signal conversion such as EFM demodulation, it becomes a 2'S complement 16-bit quantized signal, which is then D/A
It is converted into an analog signal by the converter 1, and L
This becomes the audio reproduction output signal of the channel and R channel.

This audio reproduction output signal is supplied to a speaker via an amplifier or the like (not shown).

On the other hand, the audio signal S obtained by mixing the L and R audio reproduction output signals through resistors R ₁ and R ₂ with large resistance values is input to one side of the comparator 2, and the other input to the comparator 2 is used as a comparison standard. Voltage
Give Vref.

Comparator 2 keeps output A “H” while S>Vref
and when S≦Vref, output A is set to “L”.

Therefore, if the reference voltage Vref is set to a level that makes the audio signal S silent, the presence or absence of the audio signal S can be determined based on "H" or "L" of the output A of the comparator 2. .

Simultaneously with the output A of this comparator 2, a subcode signal (P
The microcomputer 3 performs the following judgment and processing operations, and controls the disk drive system 4 and optical pickup drive system 5 based on the results, thereby always maintaining the preset values. It is possible to create almost constant intervals between songs.

Next, an example of the operation of the microcomputer 3 when creating a song interval using the output A and Q signals of the comparator 2 will be explained with reference to FIGS. 3 to 6.

(1) When the next song to be played is after the currently playing song As shown in the flowchart of Figure 3, after the start of playback, the output A of the comparator 2 becomes "L".
It is determined whether the MNR has changed, and if A becomes "L" or the MNR changes, it is determined that the song has ended and a counter is set.

This counter is built into the microcomputer 3 and serves as a timer for measuring the time between songs. For example, if it is desired to set the time between songs to 4 seconds, it is set to 4 seconds. It is assumed that at the same time as it is set, it is subtracted by a clock pulse.

In addition, to see changes in MNR, see Figure 1.
Even if there is no clear gap between songs, such as between Music 3 and Music 4, if you want to create a gap between songs at the transition point,
Omit this if it is not necessary.

After setting the counter, it is determined whether the beginning of the next song has been detected depending on whether .

If X becomes "01" before the counter reaches 0, the player is set to "pause" to wait, and when the counter becomes 0, the player is set to "play" to start playback.

If the counter reaches 0 before X reaches "01", the program immediately fast-forwards, searches for X "01" (to find the beginning of the next song), and selects "Play". Since the search distance in this case is short, the search time is about 0.5 seconds or less.

In this way, the time between songs will be approximately the set time (for example, 4 seconds) with only an error of 0 to 1.5 seconds from when X becomes "01" until the audio signal is actually played. It becomes constant.

FIG. 4 is a flowchart showing another embodiment. The process up to the counter setting is the same as FIG. 3, but after setting the counter, it is immediately fast forwarded to
Search for ``Pause'' at the beginning of the next song, wait until the counter reaches 0, and then press ``Play''.

Even in this case, it is possible to create a fixed interval between songs based on the time set in the counter.

(2) When the next song to be played is not after the currently playing song In the case of program selection, etc., the next song to be played is often not after the currently playing song. In that case, the inter-song intervals are created as shown in the flowchart of FIG.

During playback, determine whether the output A of comparator 2 has become “L” and whether the MNR has changed, and if either is YES.
When this happens, setting the counter to the time between songs (for example, 4 seconds) is the same as in case (1) above, but the subsequent processing is different.

If A becomes "L" and the counter is set, then it is determined whether the MNR has changed and whether the counter has reached t ₄ min (minimum time required for search), and the counter is set to t _{4 min} . before reaching min
If the MNR changes, the next song to play is X “01”
Search (cue) and set it to "pause", wait until the counter reaches 0, and then select "play" to start playback.

If the counter reaches t ₄ min before the MNR changes, the index number X of the next song to be played immediately (if it is specified to play from the beginning of the song, it is "01") , in the middle of a song, such as the 2nd, 3rd, etc., or the 2nd and 3rd movements.
If it is specified to play from a movement, etc., search for that index number (any one of "02" to "99") and set it to "Play."

First, when the MNR changes and the counter is set, the index number of the next song to be played is searched and set to "pause", and the counter is set to "play" after waiting for it to become 0.

Now, if you create gaps between songs in this way,
The amount of error that occurs in the actual time between songs will be examined in comparison with the case where the song gaps are created using only subcodes (in this case, the Q signal).

t ₁ : After the audio signal actually disappears
Time until MNR changes tX: Time of “00” t ₃ : Time from detecting the index number of the next song until the audio signal is actually output t ₄ : Time required for search (min 0.5 seconds, (The maximum time is 2 seconds.) T: Set time between songs τ: Error with respect to T The actual time between songs is t ₀ + T + t ₃ if the song interval is created only by sub-chords, and as shown in Figure 5. According to Fuchart, T+t ₄ max−
It can be expressed as t ₄ min + t ₃ .

Then, the error with respect to T is the error due to the former τ ₁
= t ₀ + t ₃ , error due to the latter τ ₂ = t ₄ max − t ₄ min + t ₃
becomes.

Here, t ₀ and t ₃ completely depend on the disk side, and t ₀ can be about 1 to 10 seconds, and t ₃ can be 0.
Since it is about 1.5 seconds, τ ₁ is 1 to 11.5 seconds.

On the other hand, since t ₄ min is about 0.5 seconds and t ₄ ax is about 2 seconds, τ ₂ is 1.5 to 3 seconds, which shows that the error is extremely small.

FIG. 6 is a flowchart showing another embodiment. After setting the counter in the same manner as the example in FIG. Wait for the counter to reach 0, then select "Play".

Even in this case, it is possible to create a substantially constant interval between songs as in the above embodiment.

Next, an example of the operation of the microcomputer 3 when creating a song interval using the output A of the comparator 2 shown in FIG. 2 and the P signal of the subcode will be explained with reference to FIG.

During reproduction, it is determined whether or not the output A of the comparator 2 has become "L", and when it has become "L", the counter is set to a required time between songs, and the next song to be played is searched.

In this case, the search is performed by counting the "H" level of the P signal, so it takes some time, but it determines the fall of the P signal at the beginning of the song to be played next (heading). If the cue is completed before the counter reaches 0, the game is set to "pause" and put on standby, and the game is set to "play" after waiting for the counter to reach 0.

If the counter reaches 0 before cueing is completed, play is started immediately when the P signal falls due to cueing.

Even in this case, the time between songs can be set to be a preset, substantially constant time.

In each of these embodiments, it was determined that the song ended immediately when the output A of the comparator 2 became "L," but if there was a slight silent part in the song, it was determined that the song ended. Since there is a risk of erroneous judgment, to deal with this, it is necessary to determine that the signal has ended when the state in which the signal becomes "L" continues for a predetermined period of time, or to set a predetermined value on the input side of the audio signal S of the comparator 2. It is recommended to have a time constant of .

Effects As explained above, according to this invention,
The signal that detects when the playback output of the audio signal is lost and the subcode signal are used to accurately control the time between songs to a preset time, so the information recording status on the compact disc side and the sequential playback are controlled accurately. Alternatively, the time between songs during playback can be kept substantially constant regardless of playback based on program song selection.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a signal format in the information recording area of a compact disc;
FIG. 2 is a block circuit diagram showing only the main parts of a CD player embodying the present invention, and FIGS. 3 to 7 are flowcharts showing different examples of operations for creating gaps between songs by the microcomputer in FIG. 2. It is a chart diagram. 1...D/A converter, 2...Comparator, 3...Microcomputer, _R1 , _R2 ...Resistor.

Claims (1)

[Claims] 1 In a compact disc player, when the audio signal played from the compact disc falls below a preset level, it is determined that the song has ended, and measurement of a preset time is started, and then the beginning of the next song to be played is is detected by the subcode signal, and if the beginning of the next song to be played is detected before the measurement of the set time is finished, the start of playback is delayed by waiting until the measurement of the set time is finished. and when the measurement of the set time is finished before detecting the beginning of the next song to be played, the method immediately fast-forwards, detects the beginning of the next song to be played, and starts playing. A method for making the interval between songs constant.