JP2007280584A - Data receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data receiver capable of preventing deterioration of a tone quality of audio data output from the data receiver when a recording medium is played back by a player, whereon audio data and video data are recorded, in a system to transmit the audio data to the data receiver from the player by using a digital interface. <P>SOLUTION: The data receiver is equipped with such a control means 15 that a transmitting side clock is adjusted so that the transmitting side clock and a receiving side clock detected from the input audio data are synchronized, a confirmation is made whether a receiver clock control mode for synchronizing the receiving side clock and transmitting side clock is carried out or not, and when response such as unable to carry out the receiver clock control mode is received from the receiver, the controls are carried out for storing the input audio data to a storage means and for reading out the audio data from the storage means in accordance with the receiving side clock to be formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a data receiving apparatus that receives data via a digital interface.

  A playback device for playing back digital data (video data, audio data, etc.) recorded on a recording medium such as a DVD (Digital Versatile Disc), and receiving the digital data played back from the playback device, There is a system including an amplifying device that amplifies and outputs the amplified signal to a speaker. In recent years, in this system, a digital interface such as an IEEE (Institute of Electrical and Electronic Engineers) 1394 interface has been used for transmission of audio data from a reproduction apparatus to an amplification apparatus, and audio data reproduced by the reproduction apparatus is converted into high-quality digital data. Data can be transmitted to the amplifier.

  In a system that transmits audio data from a playback device to an amplification device using a digital interface, the master clock generated by the clock generation unit of the amplification device and the master clock generated by the clock generation unit of the playback device may not be synchronized. . In this case, since jitter occurs in the audio data received from the playback device, the amplifying device cannot correctly demodulate the received audio data, and noise is generated in the audio signal output from the speaker or the audio signal is May be interrupted.

  As a method of synchronizing the master clock of the reproduction device and the amplification device, the amplification device generates a master clock synchronized with the audio data transmitted from the reproduction device, and the audio data transmitted from the reproduction device using the master clock is generated. A method of demodulating is disclosed in Patent Document 1. Hereinafter, the operation mode synchronized by this method is referred to as a transmitter clock control mode in this specification.

  As another method, the amplifying apparatus detects whether or not the master clock generated by the clock generation unit and the digital data transmitted from the reproduction apparatus are synchronized, and the generated master clock and the audio data are Patent Document 2 discloses a method for generating correction information for correcting a synchronization shift and transmitting the correction information to a playback apparatus. In this method, the playback device adjusts the frequency of the master clock based on the correction information received from the amplification device, encodes audio data using the adjusted master clock, and transmits the encoded audio data to the amplification device. Hereinafter, the operation mode synchronized by this method is referred to as a receiver clock control mode in this specification.

JP-A-6-296173 JP 2003-32572 A

  In the method (transmission device clock control mode) in which the amplification device disclosed in Patent Document 1 generates a master clock synchronized with the master clock of the reproduction device and synchronizes the master clock of the reproduction device and the amplification device, the master in the amplification device A PLL (Phase Locked Loop) circuit using a clock oscillated from a VCO (Voltage Controlled Oscillator) circuit is used to generate the clock. In this VCO circuit, since the allowable range of clock synchronization is ± 1000 ppm (Parts Per Million) with respect to the center frequency of the clock, jitter is generated in the generated master clock. For this reason, when the audio data transmitted from the reproduction device is demodulated using the master clock generated by the VCO circuit in the amplification device, jitter occurs in the audio data, and the sound quality of the audio data output from the amplification device deteriorates. There is a problem of doing.

  A method of adjusting the master clock frequency of the reproduction device to synchronize the master clock of the reproduction device and the amplification device so as to be synchronized with the master clock generated by the amplification device disclosed in Patent Document 2 (receiver clock control mode) In the amplifying apparatus, adjustment is made so that the master clock of the reproducing apparatus is synchronized with the master clock of the amplifying apparatus. Since the audio data transmitted from the playback device is synchronized with the master clock of the amplification device, no jitter occurs in the audio data received from the playback device in the amplification device. For this reason, the amplification device can reproduce the audio data received from the reproduction device with high sound quality. However, since the master clock for audio transmission of the playback device is synchronized with the master clock of the amplification device, the video master clock and the audio master clock cannot be synchronized in the playback device, and the video data to be played back This causes a problem that the moving image stops for a moment or skips and plays back one frame image.

  From the above, in a system in which audio data is transmitted between a playback device and an amplification device using a conventional digital interface, the playback device has audio data such as DVD-AUDIO or CD-DA (Compact Disc-Digital Audio). In the case of reproducing a recording medium on which only the information is recorded, the master clock of the reproducing apparatus and the amplifying apparatus is synchronized in the above-described receiving apparatus clock control mode. Therefore, the amplifying apparatus can reproduce the audio data received from the reproducing apparatus with high sound quality.

  On the other hand, when the reproducing apparatus reproduces a recording medium on which audio data and video data such as DVD-VIDEO are recorded, the moving image of the reproduced video data stops momentarily when the receiving apparatus clock control mode is used. Since problems such as skipping frames of images occur, the master clocks of the reproduction device and the amplification device are synchronized in the above-described transmission device clock control mode.

  That is, when the playback device plays back a recording medium on which audio data and video data are recorded, when the transmission device clock control mode is used, the video of the played back video data stops momentarily or an image for one frame It is possible to prevent the occurrence of problems such as skipping playback. However, in the transmission device clock control mode, the amplifier demodulates the audio data transmitted from the reproduction device using the master clock generated by the VCO circuit, so that jitter occurs in the audio data and the sound quality deteriorates.

  The present invention has been made to solve the above problems, and in a system that transmits audio data from a playback device to a data reception device using a digital interface, the playback device records audio data and video data. When playing back a recording medium, the sound quality of the audio signal output from the data receiving device is prevented from being degraded, and the video data video stops for a moment or skips one frame of image and plays back. The present invention provides a data receiving apparatus that does not need to be performed.

  In order to solve the above problems, the invention according to claim 1 of the present application is a data receiving device that receives audio data transmitted from a playback device via a digital interface, and inputs the audio data via the digital interface. Operation of the data receiving device, input means for performing signal processing on the audio data input by the input means, output means for outputting the audio data subjected to signal processing by the signal processing means, Clock generating means for generating a receiving clock to be controlled, storage means for storing audio data, a transmitting clock detected from audio data input from the input means, and a receiving clock generated by the clock generating means Adjust the transmitter clock to synchronize with the receiver The playback device confirms whether or not to use the receiver clock control mode for synchronizing the lock and the transmission side clock, and if there is a response from the playback device that the receiver clock control mode cannot be set, it is input from the input means. And control means for controlling the audio data to be stored in the storage means, and for controlling the audio data to be read from the storage means in accordance with the reception side clock generated by the clock generation means.

  The invention according to claim 2 of the present application is the data receiving device according to claim 1, further comprising detection means for detecting silence from the audio data stored in the storage means, wherein the control means comprises: The detection means controls the storage means to stop storing audio data and to erase the stored audio data in response to detection of silent audio data.

  According to the present invention, in a system that transmits audio data from a playback device to a data reception device using a digital interface, when the playback device plays back a recording medium on which audio data and video data are recorded, the data reception device To provide a data receiving apparatus that prevents deterioration of the sound quality of an output audio signal and that does not cause problems such as a momentary stop of a video data moving image or skipping and reproducing an image of one frame. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a data receiving apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is an input unit, 2 is an analog audio input unit, 3 is a digital audio input unit, 4 is an IEEE 1394 interface (IEEE 1394 I / F), 5 is an IEEE 1394 input unit, 6 is a RAM (Random Access Memory), 7 is PLL circuit, 8 is an ADC (Analog to Digital Converter), 9 is a DIR (Digital Interface Receiver), 10 is a DSP (Digital Signal Processor), 11 is a DAC (Digital to Analog Converter), 12 is an amplifier, and 13 is an output unit , 14 indicates a clock generation unit, and 15 indicates a control unit. The data receiving apparatus of this embodiment is an amplifying apparatus such as an AV (Audio Visual) amplifier.

  The input unit 1 shown in FIG. 1 includes an analog audio input unit 2, a digital audio input unit 3, and an IEEE 1394 I / F 4. The analog audio input unit 2 inputs an analog audio signal output from a playback device such as a DVD player. The analog audio input unit 2 includes an input terminal for inputting analog audio signals of a plurality of channels. The digital audio input unit 3 inputs digital audio data output from the playback device.

  The IEEE 1394 I / F 4 is a digital interface compliant with the IEEE 1394 standard, and includes an IEEE 1394 input unit 5, a RAM 6, and a PLL circuit 7. The IEEE 1394 input unit 5 inputs IEEE 1394 digital data output from the playback device via the IEEE 1394 serial bus, and demodulates the input IEEE 1394 digital data into digital audio data. The RAM 6 stores IEEE digital data input to the IEEE 1394 input unit 5 under the control of the control unit 15. The IEEE digital data stored in the RAM 6 is demodulated into digital audio data by the IEEE 1394 input unit 5.

  The digital audio data demodulated by the IEEE 1394 input unit 5 is input to the DSP 10. The PLL circuit 7 includes a VCO circuit, and generates a master clock synchronized with digital data input to the IEEE 1394 input unit 5 using a clock oscillated from the VCO circuit under the control of the control unit 15. The master clock generated by the PLL circuit 7 is used by the IEEE 1394 input unit 5 to demodulate the input IEEE 1394 digital data.

  The ADC 8 converts the analog audio signal input from the analog audio input unit 2 into digital audio data for each channel. The converted digital audio data is input to the DSP 10. The DIR 9 demodulates the digital audio data input from the digital audio input unit 3 and inputs the demodulated digital audio data to the DSP 10.

  The DSP 10 performs various surround format signal processing and the like on the digital audio data input from the ADC 8, DIR 9, or IEEE1394 input unit 5. The DAC 11 converts the digital audio data subjected to signal processing by the DSP 10 into an analog audio signal. The amplifying unit 12 amplifies the analog audio signal input from the DAC 11. The amplified analog audio signal is output from a speaker (not shown) connected to the output unit 13 for each channel. The clock generation unit 14 generates a master clock that controls the operation of the data receiving apparatus of this embodiment.

  The control unit 15 comprehensively controls the data receiving apparatus according to this embodiment. The control unit 15 transmits / receives commands to / from a playback device connected via the IEEE 1394 serial bus via the IEEE 1394 I / F 4. In the data receiving apparatus according to the present embodiment, when communication with the reproducing apparatus via the IEEE1394 interface is started, the control unit 15 determines whether or not the reproducing apparatus can operate in the receiving apparatus clock control mode to synchronize with the reproducing apparatus. Send a command to confirm.

  When receiving a command permitting the operation in the reception device clock control mode from the playback device, the control unit 15 performs control to synchronize in the reception device clock control mode. In this embodiment, as in the prior art, when the playback device plays back audio data recorded on a recording medium such as DVD-AUDIO or CD-DA, the playback device permits operation in the receiver clock control mode. To do.

  When operating in the receiver clock control mode, the control unit 15 inputs the master clock generated by the clock generation unit 14 to the IEEE 1394 input unit 5. The IEEE 1394 input unit 5 demodulates the input IEEE 1394 digital data into digital audio data using the master clock input from the clock generation unit 14.

  Then, the control unit 15 detects whether or not the master clock generated by the clock generation unit 14 is synchronized with the digital data transmitted from the playback device, and corrects the synchronization deviation between the master clock and the audio data. Are generated in accordance with a protocol defined by IEEE 1394 via the IEEE 1394 I / F 4 to generate FAST (+ 1%), SLOW (-1%), and STANDARD (0%) commands. That is, when the synchronization deviation is within a predetermined frequency range, the control unit 15 generates a STANDARD command, and a master clock (hereinafter referred to as a transmission side clock) generated by a clock generation unit built in the playback device is generated. When it is detected that a predetermined frequency is lower than a master clock (hereinafter referred to as a receiving side clock) generated by the clock generator 14, a FAST command is generated, and in the opposite case, a SLOW command is generated and sent to the playback device. Send it out.

  When receiving the FAST, SLOW, and STANDARD commands, the playback device controls the frequency of the transmission side clock to be generated according to the commands. That is, in the playback device, when the STANDARD command is received, the current frequency of the transmission side clock is maintained, and when the FAST command is received, the frequency of the transmission side clock is increased by 1% and the SLOW command is changed. When received, the frequency of the transmission side clock is lowered by 1%.

  On the other hand, when playing back audio data and video data recorded on a recording medium such as DVD-VIDEO, the playback device disables the operation in the receiver clock control mode, and the data receiver receives the receiver clock control mode operation. Send a disabled command. When the control unit 15 receives a command that disables the operation in the reception device clock control mode from the playback device, the control unit 15 causes the clock generation unit 14 to generate the reception side clock and inputs the reception side clock to the IEEE 1394 input unit 5. do.

  The control unit 15 controls to store the IEEE 1394 digital data input to the IEEE 1394 input unit 5 in the RAM 6 and controls to read the IEEE 1394 digital data stored in the RAM 6 and demodulate it into digital audio data. The IEEE 1394 input unit 5 stores, reads, and demodulates IEEE digital data using the receiving side clock.

  At this time, the playback device plays back the audio data and video data recorded on the recording medium using the transmission side clock generated by the built-in clock generation unit according to the transmission device clock control mode. Then, the reproduced audio data is output from the IEEE 1394 digital interface as IEEE 1394 digital data. The reproduced video data is output to a display device such as a monitor connected to the reproducing device.

  In this way, in the reproducing apparatus, the audio data and the video data recorded on the recording medium are reproduced in the transmitting apparatus clock control mode, so that the video master clock and the audio master clock of the transmitting clock are synchronized. For this reason, the problem that the moving image of the video data output from the display device stops for a moment or skips and reproduces one frame image does not occur.

  In the prior art, when the operation to synchronize with the reproduction device cannot be performed in the reception device clock control mode, the operation is switched to the operation to synchronize with the reproduction device in the transmission device clock control mode using the PLL circuit. On the other hand, in the data receiving apparatus of the present embodiment, the IEEE 1394 digital data received from the reproducing apparatus using the receiving clock generated by the clock generating unit 14 without performing the operation for synchronizing with the reproducing apparatus. The operation of demodulating is performed. For this reason, it becomes impossible to synchronize with the playback apparatus, and there is a possibility that the IEEE 1394 digital data received from the playback apparatus cannot be demodulated correctly.

  However, in order to solve this problem, the data receiving apparatus of the present embodiment temporarily stores the IEEE digital data received from the reproducing apparatus in the RAM 6 and reads the IEEE digital data from the RAM 6 at a reading speed suitable for demodulation. Absorb the generated jitter. Therefore, the data receiving apparatus according to the present embodiment can correctly demodulate the IEEE digital data read from the RAM 6 by using the reception side clock generated by the clock generation unit 14. For this reason, the data receiving apparatus according to the present embodiment correctly demodulates IEEE 1394 digital data input from the reproducing apparatus via the IEEE 1394 interface even when the reproducing apparatus reproduces a recording medium on which audio data and video data are recorded. Therefore, it is possible to prevent deterioration of the sound quality of the output analog audio signal.

  Here, since the IEEE digital data received from the playback device is temporarily stored in the RAM 6 in the data receiving device of this embodiment, the analog audio signal output from the speaker and the analog audio signal output from the display device A shift occurs in the synchronized video signal. In general, humans can recognize the difference between video and sound when the difference between video and sound is several tens of milliseconds or more. For this reason, the RAM 6 provided in the data receiving apparatus of this embodiment has a storage capacity capable of storing IEEE digital data corresponding to an analog audio signal of several tens of milliseconds or less.

  As described above, in the data receiving apparatus of the present embodiment, when the IEEE digital data received from the reproducing apparatus is stored in the RAM 6, the reception side clock generated by the clock generation unit 14 and the transmission side clock of the reproducing apparatus are The frequency is different. If the frequencies of the receiving clock and the transmitting clock are different, an overflow or underflow may occur in the RAM 6 due to the difference between the clock frequencies.

  An overflow occurs in the RAM 6 when the frequency of the reception side clock is lower than the frequency of the transmission side clock, that is, when the writing speed of the IEEE digital data to the RAM 6 is higher than the reading speed. On the other hand, underflow occurs in the RAM 6 when the frequency of the reception side clock is higher than the frequency of the transmission side clock, that is, when the writing speed of the IEEE digital data to the RAM 6 is lower than the reading speed.

  In order to prevent overflow and underflow of the RAM 6, the control unit 15 sets an upper limit threshold and a lower limit threshold in the RAM 6 and monitors the storage capacity of the IEEE digital data. When the storage amount of the IEEE digital data stored in the RAM 6 is larger than the upper limit threshold value or the storage capacity of the IEEE digital data stored in the RAM 6 is smaller than the lower limit threshold value, the control unit 15 In the apparatus clock control mode, control is performed to switch to an operation that synchronizes with the playback apparatus.

  The control unit 15 stops the input of the receiving side clock from the clock generation unit 14 to the IEEE 1394 input unit 5, and controls the PLL circuit 7 to generate a master clock synchronized with the IEEE digital data input from the IEEE 1394 input unit 5. To do. The IEEE 1394 input unit 5 demodulates the input IEEE 1394 digital data using the master clock generated by the PLL circuit 7.

  As described above, in the data receiving apparatus according to the present embodiment, it is possible to prevent the RAM 6 from overflowing and underflowing by synchronizing with the reproducing apparatus in the transmitting apparatus clock control mode from an asynchronous state with the reproducing apparatus. When the IEEE digital data is stored in the RAM 6 to such an extent that overflow or underflow does not occur, the control unit 15 controls to perform the operation before switching to the operation of the transmission device clock control mode.

Next, a data receiving apparatus according to the second embodiment of the present invention will be described.
FIG. 2 is a block diagram showing the configuration of the data receiving apparatus according to the second embodiment of the present invention. In FIG. 2, the same components as those of the data receiving apparatus of the first embodiment shown in FIG.

  The silence detection unit 16 shown in FIG. 2 detects silence from the digital audio data of IEEE digital data stored in the RAM 6 under the control of the control unit 15. The silence detection unit 16 outputs a detection signal to the control unit 15 when silence is detected. FIG. 3 is a diagram showing sample data of digital audio data stored in the RAM 6. FIG. 3 shows sample data of 16-bit digital audio data of LPCM (Linear Pulse Code Modulation) system reproduced from DVD-VIDEO.

  When the sample data stored in the RAM 6 is 0000h, the silence detector 16 detects silence digital audio data and outputs a detection signal to the controller 15. The control unit 15 controls to delete the digital audio data (sample data) stored in the RAM 6 when the silence detection unit 16 detects silence continuously for a predetermined number of times.

  For example, as shown in FIG. 3, when the sample data of 0000h is continuous for 8 samples, the silence detection unit 16 detects silence for 8 times continuously, so that the control unit 15 detects the digital data stored in the RAM 6. Control to delete audio data. The control unit 15 performs control for erasing the digital audio data stored in the RAM 6 and then stores the digital audio data of the IEEE digital data input from the IEEE 1394 input unit 5 to the RAM 6.

  In this embodiment, the silence detector 16 detects 0000h sample data and determines that it is silent. However, when a predetermined number of minute level sample data such as 0002h and 0001h continues in addition to 0000h, the controller 15 May control the digital audio data stored in the RAM 6 to be erased.

  As described above, in the data receiving apparatus of this embodiment, when a predetermined number of silent digital audio data is continuously stored in the RAM 6, the digital audio data stored in the RAM 6 is controlled to be erased. Therefore, the data receiving apparatus according to the present embodiment can prevent an overflow or underflow of the RAM 6 that occurs when the frequencies of the receiving clock and the transmitting clock are different.

  As described above, the present embodiment has been described using the IEEE 1394 interface as the digital interface, but an HDMI (High Definition Multimedia Interface) interface may be used.

1 is a block diagram showing a configuration of a data receiving apparatus according to a first embodiment of the present invention. The block diagram which shows the structure of the data receiver which is the 2nd Example of this invention. The figure which shows the sample data of the digital audio data memorize | stored in RAM6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Input part, 2 ... Analog audio input part, 3 ... Digital audio input part, 4 ... IEEE1394 interface, 5 ... IEEE1394 input part, 6 ... RAM, 7 ... PLL circuit, 8 ... ADC, 9 ... DIR, 10 ... DSP 11 ... DAC, 12 ... amplification unit, 13 ... output unit, 14 ... clock generation unit, 15 ... control unit, 16 ... silence detection unit

Claims (2)

In a data receiving device that receives audio data transmitted from a playback device via a digital interface,
Input means for inputting audio data via a digital interface;
Signal processing means for performing signal processing on the audio data input by the input means;
Output means for outputting audio data subjected to signal processing by the signal processing means;
Clock generating means for generating a receiving side clock for controlling the operation of the data receiving device;
Storage means for storing audio data;
A receiving apparatus for adjusting the transmitting clock so that the transmitting clock detected from the audio data input from the input means and the receiving clock generated by the clock generating means are synchronized, and to synchronize the receiving clock and the transmitting clock. Control that confirms whether or not to perform clock control mode with the playback device, and if there is a response from the playback device that the receiver device clock control mode cannot be performed, the audio data input from the input means is stored in the storage means And a control means for controlling the audio data to be read from the storage means in accordance with the receiving-side clock generated by the clock generation means. In the data receiving device according to claim 1,
Further comprising detection means for detecting silence from the audio data stored in the storage means,
The data receiving apparatus according to claim 1, wherein the control means controls the storage means to stop storing audio data and to erase the stored audio data in response to detection of silence by the detecting means.

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