JP3294996B2 - Digital audio signal playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio signal reproducing apparatus which makes it possible to determine an operation mode in a programmable manner and to prevent generation of abnormal noise at a mode change point.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in digitalization of audio / video equipment, and many of them have a plurality of recording modes. For example, some video devices support both PAL and NTSC, and many audio devices support a plurality of sampling frequencies and quantization bit numbers.

As a conventional example of such a digital audio signal reproducing apparatus for reproducing audio data recorded in a plurality of modes, there is Japanese Patent Laid-Open No. 4-117671. Hereinafter, a conventional digital audio signal reproducing apparatus will be described with reference to FIGS.
It will be described based on.

FIG. 4 shows a conventional digital audio signal reproducing apparatus. 21 is a demultiplexer, 22 is a decoder, 23 is a mute unit, 24 is a control unit, 25 is a latch, and 26 is a coincidence detector.

[0005] A reproduction signal in which the reproduction audio signal and the reproduction identification mode are multiplexed is separated by a demultiplexer 21 into a reproduction audio signal and a reproduction identification signal. The reproduced audio signal is subjected to a decoding process such as a deinterleaving process for rearranging the audio signal in accordance with the time series and an error data interpolation process in the decoder 22. The output signal of the decoder 22 is output as a reproduced output audio signal through the mute unit 23.

[0006] The mute unit 23 receives a first mute control signal, which is an output signal of the control unit 24, and a second mute control signal, which is an output signal of the coincidence detector 26.
Mutes the output signal of

The control section 24 determines an operation mode command based on the reproduction identification signal from the demultiplexer 21 and sends the operation mode command to the demultiplexer 21 and the decoder 22. Further, it is determined whether or not the operation mode indicated by the reproduction identification signal is a mode corresponding to the reproduction apparatus. If the operation mode is not supported, the first mute control signal is activated to mute, thereby generating abnormal noise. To prevent

For example, in a place where the decoder only supports a sampling frequency of 32 kHz,
When the digital audio signal sampled at Hz is reproduced, the control unit 24 can judge this from information included in the reproduction identification signal and mute.

The reproduction identification signal is latched by the latch 25 for a predetermined period, and is compared with the reproduction identification signal by the coincidence detector 26.
If the result of the comparison does not match, that is, if the mode has changed, the match detector 26 activates the second mute control signal, and the mute section 23 mutes the audio signal.

[0010]

FIG. 5 shows a case where the operation mode is switched from mode A to mode B.
As shown in this figure, when a delay due to serial transmission or the like occurs in signal transmission between the control unit 24 and another block,
In the above-described conventional digital audio signal reproducing apparatus, a state like a period 33 occurs in which the mute state is released in a period in which the reproduced signal does not match the operation mode command.

FIG. 6 shows a case where the operation mode is switched from the mode B to the operation mode C which is not supported by the apparatus. In this case, a state such as a period 37 occurs in which the second mute control signal and the first mute control signal are not continuous and the mute state is temporarily released.

As described above, in the above-described conventional digital audio signal reproducing apparatus, when the signal transmission between the control unit 24 and another block is delayed due to serial transmission or the like, an abnormal sound is generated in the reproduced sound. Therefore, there is a demand for a device that does not generate abnormal noise.

[0013] It is an object of the present invention to provide a digital audio signal reproducing apparatus which does not generate an abnormal sound in a reproduced sound even when a signal transmission between a control unit and another block is delayed due to serial transmission or the like. And

[0014]

A digital audio signal reproducing apparatus according to the present invention compares a reproduction identification signal output from a demultiplexer with an operation mode command output from a control unit, and performs a second operation.
The mute unit is controlled using the coincidence detector that outputs the mute control signal of the above.

According to the present invention, it is possible to prevent noise generation at a mode change point regardless of the signal transmission time between the control unit and other blocks even when the mode is switched.

[0016]

A digital audio signal reproducing apparatus according to a first aspect of the present invention comprises a demultiplexer for separating a reproduced audio signal and a reproduction identification signal from a reproduction signal in which an audio signal and an identification signal are multiplexed; A control unit that inputs an identification signal and outputs an operation mode command and a first mute control signal; a decoder that decodes the reproduced audio signal according to the operation mode command; and compares the reproduction identification signal with the operation mode command. A match detector for outputting a second mute control signal, and a mute unit for muting the output signal of the decoder with the first mute control signal and the second mute control signal. The operation mode indicated by the reproduction identification signal separated from the reproduction signal by the demultiplexer in the detector and the operation mode from the control unit By comparing the signal input to the decoder that performs the actual signal processing with the operation mode command mode that determines the operation mode (decode mode) of the decoder, and detects abnormal noise due to the mode change. Can be reliably prevented. Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1) FIG. 1 shows a digital audio signal reproducing apparatus according to the present invention. Reference numeral 11 denotes a demultiplexer that separates a reproduction signal into a reproduction audio signal and a reproduction identification signal.
Reference numeral 2 denotes a decoder for decoding the reproduced audio signal output from the demultiplexer. Reference numeral 13 denotes a mute unit, which outputs an output signal from the decoder 12 to a first mute control signal output from the control unit 14 and a second output from the match detector 15. Mute with mute control signal. A control unit 14 receives a reproduction identification signal output from the demultiplexer 11 as an input signal, outputs an operation mode command to the demultiplexer 11, the decoder 12, and the coincidence detector 15, and outputs a first mute control signal to the mute unit 13. Output.

Reference numeral 15 denotes a coincidence detector, which is a demultiplexer 1
The operation mode indicated by the reproduction identification signal output by the control unit 1 is compared with the operation mode command output by the control unit, and a second mute control signal is output to the mute unit 13.

The operation of the digital audio signal reproducing apparatus of the present invention configured as described above will be described below. First, a reproduction signal in which the reproduction audio signal and the reproduction identification mode are multiplexed is separated by the demultiplexer 11 into a reproduction audio signal and a reproduction identification signal. The reproduced audio signal is subjected to a decoding process such as a deinterleaving process for rearranging the audio signal according to its time series and an error data interpolation process in the decoder 12. The output signal of the decoder is
3 and output as a reproduced output audio signal.

The mute unit 13 mutes the output signal of the decoder unit in accordance with a first mute control signal which is an output signal of the control unit 14 and a second mute control signal which is an output signal of the coincidence detector 15.

The control unit 14 determines an operation mode command based on the reproduction identification signal from the demultiplexer 11, and sends the operation mode command to the demultiplexer 11, the decoder 12, and the coincidence detector 15. Further, it is determined whether or not the operation mode indicated by the reproduction identification signal is a mode corresponding to the reproduction apparatus. If the operation mode is not supported, the first mute control signal is activated to mute, thereby generating abnormal noise. To prevent For example, 32 khz as a decoder
When a digital audio signal sampled at 48 kHz is reproduced at a location corresponding only to the sampling frequency of z, the control unit 14 can judge this from information included in the reproduction identification signal and mute. The operation up to this point is the same as the conventional example.

The difference from the conventional example is that the operation mode command output from the control unit 14 is also sent to the coincidence detector 15, and this operation mode instruction is compared with the operation mode indicated by the reproduction identification signal by the coincidence detector 15. It is in.

If the result of the comparison is a mismatch, the match detector 15 activates the second mute control signal, and the mute section 13 performs mute processing on the audio signal. 2 and 3 show the timing of generating the mute control signal in the embodiment.

FIG. 2 shows a case where the operation mode indicated by the reproduction identification signal is switched from mode A to mode B. The frame in the figure is the minimum time unit at which the mode of the reproduction signal is switched. For example, in the case of an audio signal recorded together with an NTSC or PAL video signal, the video frame corresponds to an audio frame. In general, mode switching is performed.

Here, one frame is transmitted when the reproduction identification signal is transmitted from the demultiplexer 11 to the control unit 14, and one frame is transmitted when the operation mode command is transmitted from the control unit 14 to the decoder 12 and the coincidence detector 15. Suppose a delay occurs.

The timing of the operation command mode at this time is as follows:
As shown in FIG. 2, it is delayed by two frames from the reproduction identification signal. Since the coincidence detector 15 of the present invention compares the reproduction identification signal with the operation mode command, the second mute control signal becomes active in the periods 42 and 43 in which the states of the reproduction identification signal and the operation mode command are different. By muting the audio signal by the mute unit 13 using the second mute control signal, generation of abnormal noise can be prevented.

FIG. 3 shows a case where the operation mode indicated by the reproduction identification signal is switched from mode B to operation mode C which is not supported by the apparatus. In this case, in addition to the second mute control signal being active in the periods 46 and 47 as in the case of FIG. 2, the first mute control signal output from the control unit 14 becomes active from the period 48 Become. For this reason, since the first mute control signal and the second mute control signal are continuously generated, the mute process can be performed without generating abnormal noise.

The control unit 14 can be constituted by a microcomputer, and has serial communication means for serially transmitting signals to and from other blocks.

[0029]

As described above, according to the present invention, by providing the coincidence detector for comparing the reproduction identification signal with the operation mode command, the operation mode indicated by the reproduction identification signal and the operation command mode from the control unit can be changed. By applying the audio mute at the time of non-coincidence, even when transmission of a signal with the control unit takes time, generation of abnormal noise at a mode change point can be completely prevented. Also, compared to the conventional example, the circuit can be reduced by eliminating the need for latching the identification signal, and the effect of the implementation is great.

[Brief description of the drawings]

FIG. 1 is a block diagram of a digital audio reproducing apparatus according to an embodiment;

FIG. 2 is a timing chart showing an operation when the operation mode is switched from A to B in the embodiment;

FIG. 3 is a timing chart showing an operation when the operation mode is switched to an unsupported operation mode of the device in the first embodiment;

FIG. 4 is a block diagram of a conventional digital audio reproducing apparatus.

FIG. 5 is a timing chart showing an operation when the operation mode is switched from A to B in the conventional example.

FIG. 6 is a timing chart showing an operation when the operation mode is switched to an unsupported operation mode of the device in the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Demultiplexer 12 Decoder 13 Mute part 14 Control part 15 Match detector

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Haruhisa Inoue 1 Baba Zujo, Nagaokakyo-shi, Kyoto, Japan Inside Mitsubishi Electric Engineering Co., Ltd. Inside the company (72) Inventor Hidemi Oka 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Toshihide Ishimoto 1006 Okadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-4-117671 (JP, A) JP-A-4-47560 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 20/10 321

Claims (3)

(57) [Claims] A demultiplexer for separating a reproduction audio signal and a reproduction identification signal from a reproduction signal in which an audio signal and an identification signal are multiplexed; an input of the reproduction identification signal, an operation mode command and a first mute control A control unit that outputs a signal; a decoder that decodes the reproduced audio signal in accordance with the operation mode command; and a second unit that compares the reproduction identification signal with the operation mode command.
A digital audio signal reproducing device, comprising: a coincidence detector that outputs a mute control signal of (i), and a mute section that mutes an output signal of the decoder by the first mute control signal and the second mute control signal. 2. The digital audio signal reproducing device according to claim 1, wherein the control unit comprises a microcomputer. 3. The digital audio signal reproducing apparatus according to claim 1, wherein the control unit includes a serial communication unit for serially transmitting a signal to and from another block.