JP3868390B2 - Source switching device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a source switching device, and more particularly to a MIX function that fades out a previous source and outputs the next source at the same time when the source is switched.
[0002]
[Prior art]
Most playback devices such as home audio devices and in-vehicle audio devices have playback units for various sources such as CD (Compact Disc) players, DVD (Digital Versatile Disk) players, MD (Mini Disc) players, cassette decks, and radio tuners. I have. In this type of playback device, the user can switch to a desired source and enjoy viewing music and video.
[0003]
When switching from one audio source to another, a single, large switching noise may occur. When this switching noise is output from a speaker on an amplifier, it is very annoying. Therefore, conventionally, in order to avoid the switching noise being output from the speaker, many hundreds of milliseconds have been muted at the source switching timing.
[0004]
However, when mute is applied, the sound is interrupted at that moment. Therefore, as the next stage, it is desired to avoid switching noise without causing sound interruption. As a specification for that purpose, it is conceivable that the source sound before the switching is faded out and at the same time the next source sound is faded in to mix and play back and forth sources (hereinafter referred to as the MIX function). Called).
[0005]
The MIX function is also provided in a DSP (Digital Signal Processor) used in an in-vehicle system equipped with a navigation device or a hands-free device. For example, when the navigation device uses the route guidance function, the traveling direction and the like are guided by voice when the vehicle approaches within a predetermined distance from the guidance intersection on the guidance route. At this time, when the audio source is also reproduced, the above-described MIX function is used. That is, by reducing the volume of the audio source being reproduced and outputting the guidance voice, the guidance voice can be easily heard.
[0006]
Also, when a call is received with a hands-free device, the volume of the audio source being played is reduced and the voice of the telephone is output so that the call voice and the other party's voice can be easily heard. Thus, the MIX function of the DSP is used when outputting the guidance voice of the navigation device and the telephone voice of the hands-free device while outputting the voice of the audio source.
[0007]
The DSP having the MIX function has two primary and secondary audio processing systems. The audio source is assigned to primary, and the information source such as guidance voice and telephone voice is assigned to secondary. Normally, the playback sound of the audio source is output using the primary, but when outputting an information source that suddenly enters, the primary audio source and the secondary information source are mixed and output.
[0008]
A technique has also been proposed in which the end of the previous song is faded out and the beginning of the next song is fed in when a song such as a CD is switched (see, for example, Patent Document 1). However, this is a description of the crossfade function that works when switching between songs in the same source, and requires special processing such as double-speed playback and high-speed switching of the switch. It is different from the function.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-81829
[Problems to be solved by the invention]
As described above, if the MIX function provided in the conventional DSP is used, it is possible to avoid switching noise without causing sound interruption. That is, as shown in FIG. 4, the previous source being output is faded out using the primary, and the next source to be reproduced is faded in using the secondary, so that the audio sources before and after are mixed and output. Is possible.
[0011]
However, in the conventional DSP, since the secondary assumes the output of monotonous voices such as guidance voices and telephone voices, it does not have an acoustic effect addition function such as an equalizer or loudness. For this reason, if the next audio source is assigned to the secondary and mixed, the next source after mixing will not be able to use its functions even though the equalizer and loudness are set, resulting in a flat sound. was there.
[0012]
For this reason, the MIX function cannot be used at the time of switching the audio source, and the fact is that it must be switched by muting. If the secondary is also provided with an equalizer function and a loudness function, the problem can be solved, but a large hardware change is required and the cost of the DSP increases.
[0013]
The present invention has been made in order to solve such problems, and it is possible to perform normal sound even for the next source output after switching the audio source without greatly changing the hardware configuration of the DSP. It is an object to make it possible to use the MIX function in such a way that effect addition control can be performed.
[0014]
[Means for Solving the Problems]
In order to solve the above-described problem, in the source switching device according to the present invention, when the audio source is switched, the audio source output by the first sound processing system having the acoustic effect addition function before switching is used as the acoustic effect. The second audio processing system having no additional function is switched and assigned, and the next audio source to be reproduced after the switching is assigned to the first audio processing system. Thereafter, the audio source assigned to the second sound processing system is faded out, and the audio source assigned to the first sound processing system is faded in.
[0015]
According to the present invention configured as described above, the source allocation to the audio processing system is switched before the mix processing, and the audio source that has been played so far is then played back to the second audio processing system. An audio source is assigned to the first audio processing system. The first audio processing system is provided with a sound effect addition function, and the next audio source is output by fading in from the first audio processing system, so that the next audio source output after the mix processing It is also possible to perform normal sound effect addition control.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a DSP 100 that implements a source switching apparatus according to the present invention. As shown in FIG. 1, the source switching device (DSP) 100 of this embodiment includes a microcontroller (microcomputer) 1, selectors 2 and 3, an acoustic effect adding unit 4 such as an equalizer and loudness, mute processing units 5 and 6, A mix processing unit 7 and a D / A conversion unit 8 are provided.
[0017]
The selector 2, the sound effect adding unit 4 and the mute processing unit 5 constitute a primary 10 audio processing system (corresponding to the first audio processing system of the present invention). The selector 3 and the mute processing unit 6 constitute a secondary 20 audio processing system (corresponding to the second audio processing system of the present invention). The secondary 20 is not provided with an acoustic effect adding function such as an equalizer and a loudness.
[0018]
Hereinafter, functions of each unit will be described. The microcomputer 1 controls the entire DSP 100. The selector 2 selectively switches and outputs one of a plurality of types of audio sources such as AM / FM radio, CD, and MD in accordance with control from the microcomputer 1. In accordance with control from the microcomputer 1, the selector 3 selectively outputs one of the guidance voices of the navigation device in addition to a plurality of types of audio sources such as AM / FM radio, CD, and MD.
[0019]
The sound effect adding unit 4 adds sound effects such as equalizer and loudness to the audio source selected by the selector 2. The mute processing unit 5 mutes the audio signal output from the acoustic effect adding unit 4 to lower the volume. The mute processing unit 6 mutes the audio signal output from the selector 3 to lower the volume. The mute processing units 5 and 6 are switched on / off by the microcomputer 1 and the volume is instantaneously reduced when the mute processing units 5 and 6 are turned on.
[0020]
The mix processing unit 7 performs a process of fading out one audio signal processed by the primary 10 and the secondary 20 and fading in the other audio signal. In the mix processing unit 7, ON / OFF of the MIX processing is switched by the microcomputer 1. The microcomputer 1 controls which audio signal of the primary 10 or the secondary 20 is faded out and which audio signal is faded in according to the type of the next source to be reproduced after switching.
[0021]
For example, when outputting the guidance voice of the navigation device during CD playback, the playback voice of the CD previously assigned to the primary 10 is faded out and the guidance voice of the navigation device newly assigned to the secondary 20 is used. Fade in. At this time, the reproduced sound of the CD is not completely faded out to 0 level but is lowered to a certain volume and maintained.
[0022]
Further, for example, when switching from CD playback to radio playback, before mixing processing, the CD source that has been selected by the selector 2 so far is switched to be selected by the selector 3, and the radio source is selected by the selector 2 Switch to select. That is, the assignment of the CD source is switched from the primary 10 to the secondary 20, and the radio source to be reproduced next is assigned to the primary 10. Thereafter, the CD source assigned to the secondary 20 is faded out, and the radio source assigned to the primary 10 is faded in.
[0023]
The D / A converter 8 converts the digital audio signal output from the mix processor 7 into an analog signal. The analog audio signal output from the D / A converter 8 is amplified by the amplifier 101 with a predetermined amplification factor and output from the speaker 102.
[0024]
Next, the operation of the DSP 100 configured as described above will be described with reference to the timing chart shown in FIG. FIG. 2 (a) shows the operation when the guidance voice of the navigation device is output during CD playback, and FIG. 2 (b) shows the operation when switching from CD playback to radio playback.
[0025]
In FIG. 2A, during playback of the CD source, the selector 2 selects the CD source according to the control from the microcomputer 1. As a result, the playback sound of the CD source is processed by the primary 10 and output to the mix processing unit 7. At this time, the mute processing unit 5 is set to OFF. On the other hand, the mute processing unit 6 of the secondary 20 is set to ON. The MIX function of the mix processing unit 7 is set to OFF.
[0026]
During playback of such a CD source, when the vehicle approaches within a predetermined distance from the guidance intersection on the guidance route, a predetermined command is transmitted from the outside of the DSP 100 to the microcomputer 1. The microcomputer 1 selects the guidance voice by controlling the selector 3 of the secondary 20 at the timing t1 when the command is received. Further, after the MIX function of the mix processing unit 7 is turned on, a fade-in / fade-out time is set, and the mute of the mute processing unit 6 is released.
[0027]
As a result, the playback sound of the CD assigned to the primary 10 until then fades out to a predetermined volume level, and the guidance sound of the navigation device newly assigned to the secondary 20 fades in. Thereafter, when the voice guidance is finished at a certain timing t2, the CD voice of the primary 10 fades in and the guidance voice of the secondary 20 fades out to return to the original state.
[0028]
Also in FIG. 2B, the operation during playback of the CD source before switching is the same as in FIG. That is, the CD source is selected by the selector 2 according to the control from the microcomputer 1, the mute processing unit 5 of the primary 10 is set to OFF, and the mute processing unit 6 of the secondary 20 is set to ON. Further, the MIX function of the mix processing unit 7 is set to OFF.
[0029]
During playback of such a CD source, for example, when a user instructs switching to a radio source, the instruction command is transmitted from the outside of the DSP 100 to the microcomputer 1. The microcomputer 1 switches the mute processing unit 5 to ON at the timing T1 when receiving this command, and applies a short mute for several milliseconds to the output of the primary 10. During the short time T1 to T2 during which the muting is applied, the microcomputer 1 performs the following operation.
[0030]
First, the selectors 2 and 3 are controlled to switch the source between the primary 10 and the secondary 20. As a result, the primary 10 is assigned the next source, and the secondary 20 is assigned the previous source. In other words, the CD source that has been selected by the selector 2 is switched so as to be selected by the selector 3, and the selector 2 is switched so that the next radio source is selected.
[0031]
Next, after the MIX function of the mix processing unit 7 is turned on, fade-in / fade-out times in the primary 10 and the secondary 20 are set, and the mute of the mute processing units 5 and 6 is released. As a result, the CD source that is the previous source assigned to the secondary 20 fades out, and the radio source that is the next source assigned to the primary 10 fades in.
[0032]
By performing such a mixing operation in the DSP 100, the radio source that is the next source is faded in and output from the primary 10, and the equalizer function by the sound effect adding unit 4 is also applied to the next source that is output after the mixing process. The loudness function can be applied. Moreover, the primary 10 is muted for a very short time, and the audio source that is being faded out is hardly noticeable to the user even if the equalizer function or the loudness function is not working, which is particularly problematic for hearing. There is no.
[0033]
By the way, as described above, the fade-in / fade-out times of the primary 10 and the secondary 20 are set before the mixing process, which is one of the features of the present embodiment. In the present embodiment, the microcomputer 1 sets a fade-in / fade-out time according to the type of source to be switched.
[0034]
FIG. 3 is a diagram showing an example of setting the fade-in / fade-out time. For example, in the case of an audio source such as AM / FM radio, CD, MD, DVD, and cassette tape, the fade-out time is set to about 200 milliseconds and the fade-in time is set to about 800 milliseconds. In the case of an information source such as a guidance voice of a navigation device or a telephone voice of a hands-free device, both the fade-out time and the fade-in time are set to about 200 milliseconds. The reason why the fade-in time of the information source is shorter than that of the audio source is that switching is more urgent.
[0035]
In addition, a specific priority message may be set assuming that the urgency of switching is higher, and the fade-in / fade-out time may be further shortened for the priority message (for example, 50 milliseconds or less).
[0036]
As described above in detail, according to the present embodiment, the secondary 20 is switched by switching the source of the primary 10 and the secondary 20 at a timing before applying the mute for a short time before mixing the previous source and the next source. It is dedicated to the fade-out output of the previous source. Thus, the MIX function can be used in such a way that normal sound effect addition control can be performed for the next source output after the source switching without requiring a large hardware change for the DSP 100. become.
[0037]
In addition, the said embodiment is only what showed the example of actualization in implementing this invention, and, as a result, the technical scope of this invention should not be interpreted limitedly. In other words, the present invention can be implemented in various forms without departing from the spirit or main features thereof.
[0038]
【The invention's effect】
As described above, according to the present invention, the MIX function at the time of source switching can be satisfied without requiring a large hardware change, and normal sound effect addition control can be appropriately applied to the next source after switching. Will be able to do.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a DSP in which a source switching device according to the present invention is implemented.
FIG. 2 is a timing chart showing a mixing operation at the time of source switching according to the present embodiment.
FIG. 3 is a diagram illustrating an example of fade-in / fade-out time setting;
FIG. 4 is a timing chart showing a mixing operation at the time of conventional source switching.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Microcomputer 2, 3 Selector 4 Sound effect addition part 5, 6 Mute processing part 7 Mix processing part 8 D / A conversion part 10 Primary 20 Secondary 100 DSP

Claims (3)

A source switching device that has a first sound processing system having a sound effect addition function and a second sound processing system that does not have a sound effect addition function, and performs sound output by switching to any sound processing system. And
At the time of switching from the first audio source to the second audio source, the first audio source being processed in the first audio processing system is switched and assigned to the second audio processing system before the switching. And source allocation switching means for allocating the second audio source to be reproduced after switching to the first audio processing system,
The first audio source assigned to the second audio processing system is faded out by the source allocation switching means, and the second audio source is assigned to the first audio processing system by the source allocation switching means. And a mix processing means for fading in the source switching device. The source allocation switching means performs muting when switching audio sources, and switches allocation of audio sources to the first audio processing system and the second audio processing system during the mute period. 2. The source switching device according to 1. 3. The source switching apparatus according to claim 1, further comprising fade time setting means for setting the fade-in time and the fade-out time according to the type of the source to be switched.

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