JP5166963B2 - Transmission method, transmission apparatus, and communication system - Google Patents

Description

  The present invention relates to a transmission method, a transmission apparatus, and a communication system that generate and transmit a transmission frame from data input from an external apparatus.

  In the case of transmitting streaming data such as video or audio that requires a fixed time output, the receiving device must have a mechanism for matching the data reproduction timing to the transmitting device. In the case where such data input from an external device to a transmission device is transmitted to the reception device, it is considered that the data is transmitted as a transmission frame having a continuous predetermined configuration. However, when there is a fluctuation in the data input cycle or a deviation in the operation clock frequency between the external device and the transmission device, a difference occurs between the data input rate and the transmission rate. As a result, data loss and frame discontinuity occur, and there is a problem that high-quality transmission of streaming data such as video and audio cannot be performed.

  Therefore, it is widely practiced to provide a buffer memory to absorb both speed differences and to equalize the transmission speed. However, even if a buffer memory is provided, if the fluctuation in the data input cycle is biased to one side or there is a deviation in the operating clock frequency between the external device and the transmitting device, the buffer memory overflows or underflows. Occurs.

In order to cope with the above-described problem, a technique is disclosed in which the length of a preamble constituting a frame is changed according to the accumulation amount of the buffer memory (see, for example, Patent Document 1).
JP 62-72251 A

  However, Patent Document 1 does not disclose an operation in switching external devices. In the configuration of Patent Document 1, the amount of data stored in the buffer memory instantaneously increases or decreases due to a change in data input timing when the external device is switched, and the buffer memory may overflow or underflow. . In order to prevent this, it is necessary to prepare a buffer memory that does not overflow even when the external device is switched, and to operate by storing data that does not underflow in the buffer memory.

  In this case, since an appropriate amount of data is stored in the buffer memory and operated, there is a problem that an originally unnecessary transmission delay occurs.

  An object of the present invention is to solve a problem caused by switching of operation modes in a transmission apparatus that transmits a transmission frame composed of a variable length part and a fixed length part.

The present invention is a transmission method executed in a transmission device for transmitting a transmission frame composed of a variable length part and a fixed length part,
Means for generating a reproduction synchronization signal, from a data input from an external device , generating a reproduction synchronization signal having a period corresponding to a sampling period of the input data;
Means for generating a clock signal, generating a clock signal having a period corresponding to a sampling period of data input from the external device;
A detection step of detecting means, caused by the switching of the operation mode, a signal the reproduction synchronization, detects the phase difference between the clock signal,
Frame generation means, a frame generating step of generating a transmission frame by changing the length of the variable portion in accordance with a phase difference the detection,
A transmission step of transmitting the generated transmission frame to the receiving device in synchronization with a cycle of the clock signal;
It is characterized by having.

  The present invention also provides a first operation mode for transmitting a transmission frame generated from data input from an external device, and a second operation mode for transmitting a transmission frame generated from data generated inside the transmission device. And a multi-channel acoustic data including reproduction synchronization data input from the external device, and generating acoustic data and a reproduction synchronization signal. In the case of the first operation mode, the decoder, the command data related to the system setting or the transmission data generation unit for generating null data, the acoustic data generated by the decoder is output, and the case of the second operation mode. A data selector for outputting the data generated by the transmission data generation unit, and in the case of the first operation mode, the data selector A clock selector for outputting a reproduction synchronization signal generated by a coder and controlling the signal not to be output in the second operation mode, and a clock signal having a period corresponding to the period of the reproduction synchronization signal A clock generation unit that generates the phase difference information between the reproduction synchronization signal generated by the decoder and the clock signal generated by the clock generation unit in the first operation mode, In the case of the second operation mode, an output unit that outputs predetermined phase difference information, an adjustment time determination unit that generates adjustment time information based on an output of the output unit, an output of the data selector, Based on the adjustment time information generated by the adjustment time determination unit, a data frame generation unit that generates a data frame, and the data frame generation unit A transmission unit comprising: a generation unit that generates an OFDM symbol from a data frame; a burst signal generation unit that generates a burst signal; the burst signal; the OFDM symbol; and a frame adjustment signal having a length corresponding to the adjustment time information. And generating means for generating a frame, and transmitting means for transmitting the transmission frame in synchronization with a cycle of the clock signal generated by the clock signal generating section.

  According to the present invention, it is possible to cope flexibly without degrading quality by changing the length of the variable length part included in the transmission frame in accordance with the switching of the operation mode of the transmission apparatus.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings.

  In the present embodiment, a 5.1 channel acoustic system to which the present invention is applied will be described as an example of a communication system.

  FIG. 2 is a block diagram showing a configuration example of a 5.1 channel sound system in the present embodiment. Players 200 and 201 shown in FIG. 2 read multi-channel sound data from a recording medium on which sound data such as an optical disk is recorded, and output the multi-channel sound data including reproduction synchronization data such as S / PDIF to the outside. In this embodiment, for convenience of explanation, the number of players is two, but the number of players is not limited as long as it is one or more.

  The controller 210 performs settings in the system such as delay time adjustment and volume adjustment, selects one of the acoustic data input from the players 200 and 201 based on a user instruction, and transmits it to the adapters 220 to 225.

  The adapters 220 to 225 receive the system setting data and acoustic data transmitted from the controller 210 and output them to the individually connected speakers 230 to 235. The speakers 230 to 235 output sound signals from the individually connected adapters 220 to 225.

  Acoustic channels corresponding to the installation positions of the individual speakers 230 to 235 are assigned to the adapters 220 to 225. That is, the adapter 220 is assigned to the center (C) channel, the adapter 221 is assigned to the subwoofer (SW) channel, and the adapter 222 is assigned to the front light (FR) channel. The adapter 223 is assigned to the rear right (RR) channel, the adapter 224 is assigned to the rear left (RL) channel, and the adapter 225 is assigned to the front left (FL) channel.

  The players 200 and 201 and the controller 210 are connected by an acoustic cable such as S / PDIF. The controller 210 and the adapters 221 to 225 are connected by a cable in a daisy chain format. In this example, the controller 210 and the adapter 220, the adapter 220 and the adapter 221, the adapter 221 and the adapter 222, the adapter 222 and the adapter 223, the adapter 223 and the adapter 224, and the adapter 224 and the adapter 225 are connected, respectively.

  With the configuration described above, the setting data and acoustic data transmitted by the controller 210 are received by the adapter 220 and transmitted to the adapter 221. Data received by the adapter 221 is transmitted to the adapter 222. As described above, the setting data and the acoustic data transmitted from the controller 210 are transmitted in the order of the adapter 220, the adapter 221, the adapter 222, the adapter 223, the adapter 224, and the adapter 225.

  The 5.1 channel sound system shown in FIG. 2 has four operation modes: an initial setting mode, a player A playback mode, a player B playback mode, and a synchronization holding mode. Here, the four operation modes will be described with reference to the state transition diagram shown in FIG.

  The player A reproduction mode is a reproduction mode for reproducing the player 200, and the player B reproduction mode is a reproduction mode for reproducing the player 201.

  FIG. 3 is a diagram showing an example of state transition of the 5.1 channel sound system in the present embodiment. When the system is powered on by the user, the system transitions to the initial setting mode of S301. The initial setting mode S301 is an operation mode in which the controller 210 transmits commands related to system settings such as a volume adjustment command and a delay time adjustment command to the adapters 220 to 225. Then, after the setting is completed, the process shifts to the synchronization holding mode of S302.

  The synchronization holding mode S302 is an operation mode for transmitting a signal for the purpose of synchronizing transmission and reception clocks when there is no data to be transmitted such as acoustic data and setting data. In the synchronization holding mode S302, the controller 210 continues signal transmission by transmitting non-valid data such as null data to the adapters 220 to 225.

  The player A playback mode in S303 and the player B playback mode in S304 are operation modes in which the playback data of the players (200, 201) is acoustically output based on a user instruction. When playback of the player (200 or 201) is stopped in the player A playback mode S303 or the player B playback mode S304, a transition is made to the synchronization holding mode S302. In addition, when playback is switched from the player 200 to the player 201, the player A playback mode S303 is shifted to the player B playback mode S304. Conversely, when playback is switched from the player 201 to the player 200, the player B playback mode S304 shifts to the player A playback mode S303.

  FIG. 4 is a diagram illustrating an example of a configuration of a frame transmitted in the present embodiment. The transmission frame includes a fixed-length OFDM symbol including a guard interval 402 and a valid symbol 403, a burst signal 401, and a variable time-length frame adjustment signal 404. Here, the OFDM is Orthogonal Frequency Division Multiplexing.

  Here, the burst signal 401 is a fixed-length sine wave signal transmitted for the purpose of synchronizing the transmission / reception clock. The frame adjustment signal 404 is a signal whose time length changes according to the time fluctuation of the input cycle of the acoustic data input from the players 200 and 201. The variable range of the time length of the frame adjustment signal 404 is set to be equal to or greater than the time fluctuation of the input period of the acoustic data, and a frame having a time length that matches the input period of the acoustic data including the time fluctuation is generated and transmitted. Is done.

  That is, since a frame corresponding to the deviation of the operation clock frequency of the player 200 or 201 is transmitted, an overflow or underflow of the buffer memory does not occur. Therefore, transmission can be performed without causing malfunction such as sound interruption.

  Next, the configuration and operation of the controller 210 will be described with reference to FIG.

  FIG. 1 is a block diagram showing an example of the configuration of the controller 210 in the present embodiment. In FIG. 1, reference numerals 100 and 101 denote multi-channel audio decoders (hereinafter abbreviated as decoders), which have the same configuration and operation. The decoder 100 (101) decodes multi-channel audio data including reproduction synchronization data such as S / PDIF output from the player 200 (201), and generates PCM audio data and reproduction synchronization signals for each channel. To do. The acoustic data generated here is output to the data selector 102 via the signal line 150 (152), and the reproduction synchronization signal is output to the clock selector 103 via the signal line 151 (153). The reproduction synchronization signal is generated from reproduction synchronization data (a preamble in the case of S / PDIF) output from the player 200 (201), and has a period equal to the sampling period of the acoustic data.

  Since the operation clocks of the players 200 and 201 have temporal fluctuations, the reproduction synchronization data in the audio data output from the players 200 and 201 and the reproduction synchronization signal generated from the reproduction synchronization data are also temporal. It will have a great fluctuation.

  The data selector 102 selects and outputs one of the three inputs based on the operation mode information input from the operation mode selection unit 104 via the signal line 155. Here, when the operation mode is the player A reproduction mode or the player B reproduction mode (first operation mode), the acoustic data from the decoder 100 or the decoder 101 is output to the data frame generation unit 106 via the signal line 157. . When the operation mode is the initial setting mode or the synchronization holding mode (second operation mode), the signal input from the transmission data generation unit 105 via the signal line 154 is output to the data frame generation unit 106.

  The clock selector 103 selects and outputs an input signal based on the operation mode information from the operation mode selection unit 104. Here, when the operation mode is the player A playback mode or the player B playback mode, the playback synchronization signal output from the decoder 100 or the decoder 101 is output to the phase comparison unit 111 via the signal line 158. When the operation mode is the initial setting mode or the synchronization holding mode, no signal is output.

  The operation mode selection unit 104 outputs the operation mode information selected from the four operation modes described above to the data selector 102, the clock selector 103, and the phase comparison unit 111 via the signal line 155, and the signal line 156 is output. To the transmission data generation unit 105.

  When the operation mode is the initial setting mode, the transmission data generation unit 105 generates command data related to system settings such as a volume adjustment command and a delay time adjustment command, and outputs the command data to the data selector 102 via the signal line 154. When the operation mode is the synchronization holding mode, null data is generated and output to the data selector 102.

  The data frame generation unit 106 generates the data frame shown in FIG. 5 based on the data input from the data selector 102 and the adjustment time determination unit 112.

  FIG. 5 is a diagram illustrating an example of the configuration of a data frame in the present embodiment. In FIG. 5, reference numeral 501 denotes a C channel, 502 denotes an FR channel, 503 denotes an FL channel, 504 denotes an RR channel, 505 denotes an RL channel, and 506 denotes an SW channel data area. In these data areas, acoustic data and setting data for each channel are arranged. Reference numeral 507 denotes an AUX area in which adjustment time information and operation mode information input from the adjustment time determination unit 112 are arranged. Although details of the delay time information will be described later, it is information necessary for generating a correct FFT window at the time of demodulation.

  Returning to the description of FIG. The data frame generated by the data frame generation unit 106 is output to the OFDM modulation unit 107 via the signal line 159. The OFDM modulation unit 107 performs OFDM modulation on the data frame input from the data frame generation unit 106 to generate a complex OFDM baseband signal including effective symbols and guard intervals, and transmits the complex OFDM baseband signal to the orthogonal modulation unit 108 via the signal line 160. Output.

  The orthogonal modulation unit 108 generates an OFDM passband signal by orthogonally modulating the complex OFDM baseband signal input from the OFDM modulation unit 107 and outputs the OFDM passband signal to the frame adjustment signal addition unit 109 via the signal line 161.

  The frame adjustment signal adding unit 109 generates a frame adjustment signal having a length corresponding to the adjustment time information input from the adjustment time determining unit 112 and adds the frame adjustment signal to the OFDM passband signal. A null signal or the like is used as the frame adjustment signal. The OFDM passband signal to which the frame adjustment signal is added is output to the D / A converter 110 via the signal line 162.

  The D / A conversion unit 110 D / A converts the output of the frame adjustment signal adding unit 109 based on the clock input from the clock signal generation unit 115 at the rising edge of the enable signal input from the timing signal generation unit 114. . The analog signal output from the D / A converter 110 is output to the output signal selector 117 via the signal line 163.

  The phase comparison unit 111 performs phase comparison based on the operation mode information from the operation mode selection unit 104. Here, when the operation mode is the player A reproduction mode or the player B reproduction mode, the rise time difference between the output of the clock selector 103 and the output of the frame clock generation unit 113 is counted by the clock input from the clock signal generation unit 115. The count value is output to the adjustment time determination unit 112 via the signal line 164 as a phase difference count value (phase difference information). When the operation mode is the player A playback mode or the player B playback mode, the clock selector 103 outputs a playback synchronization signal. Therefore, the phase difference between the reproduction synchronization signal and the rise time of the clock signal output from the frame clock generation unit 113 is compared, and the phase difference count value is output to the adjustment time determination unit 112. Further, when the operation mode is the initial setting mode or the synchronization holding mode, the phase difference count value 0 is output to the adjustment time determination unit 112.

  The adjustment time determination unit 112 generates adjustment time information based on the phase difference count value output from the phase comparison unit 111. The adjustment time information is output to the data frame generation unit 106, the frame adjustment signal addition unit 109, the frame clock generation unit 113, and the timing signal generation unit 114 via the signal line 165. The upper and lower limit values are set in the adjustment time information output from the adjustment time determination unit 112, and the adjustment time determination unit 112 determines that the phase difference count value input from the phase comparison unit 111 is within the upper and lower limit range. The phase difference count value is output as adjustment time information. When the phase difference count value is outside the upper and lower limit range, an upper limit value or lower limit value close to the phase difference count value is output as adjustment time information. The frame adjustment signal adding unit 109 generates a frame adjustment signal having a time length based on the adjustment time information. As a result of this operation, the variable range of the time length of the frame adjustment signal falls within a set finite length range. It will be a thing.

  The frame clock generation unit 113 divides the clock signal output from the clock signal generation unit 115 and generates a clock signal in which the rising point is changed based on the adjustment time information input from the adjustment time determination unit 112. As a result of this operation, when the operation mode is the player A playback mode or the player B playback mode, the cycle of the clock signal generated by the frame clock generation unit 113 is substantially the same as the cycle of the playback synchronization signal including time fluctuation. Become. The clock signal generated by the frame clock generation unit 113 is output to the phase comparison unit 111 and the timing signal generation unit 114 via the signal line 166.

  The timing signal generation unit 114 generates an enable signal that is at a time H level that is the sum of the OFDM symbol time and the frame adjustment signal time after a predetermined time (Δd) has elapsed since the rising edge of the clock signal output from the frame clock generation unit 113. To do. Then, the enable signal is output to the D / A converter 110 and the output signal selector 117 via the signal line 167. Here, Δd has a length of at least the longest cycle of the clock signal generated by the frame clock generation unit 113.

  The clock signal generation unit 115 outputs a clock signal to the phase comparison unit 111, the frame clock generation unit 113, the D / A conversion unit 110, the timing signal generation unit 114, and the burst signal generation unit 116 via the signal line 168. The clock signal is generated from a clock source independent of the players 200 and 201, and is a low jitter clock signal sufficient for use in the OFDM modulation / demodulation system.

  The burst signal generation unit 116 generates a transmission / reception clock synchronization signal by dividing the signal of the clock signal generation unit 115 and outputs the signal to the output signal selector 117 via the signal line 169.

  The output signal selector 117 operates based on the enable signal input from the timing signal generator 114. When the output signal selector 117 is at the H level, the output signal selector 117 selects the output of the D / A converter 110 and outputs it to the BPF 118 via the signal line 170. When the enable signal is at L level, the output of the burst signal generator 116 is selected and output to the BPF 118.

  The BPF 118 is a bandpass filter for band limitation. The signal that has passed through the BPF 118 is output to the transmission line via the signal line 169. The burst signal has its harmonics removed by the BPF 118 and becomes a sine wave signal that is output to the transmission line.

  As a result of the operation of each unit, the transmission frame shown in FIG. 4 is output to the transmission path. Further, the time length of the frame adjustment signal changes in accordance with the input period of the acoustic data including time fluctuation, and a frame having a time length that matches the input period of the acoustic data is transmitted.

Here, the detailed operation of the controller 210 will be described using a specific example. The system conditions are shown below, but the present invention is not limited to these conditions.
・ Sampling frequency of audio data: 48 kHz
-Clock frequency output by the clock signal generator 115: 90 MHz
Burst signal time: 3.28 μsec (295 MHz at 90 MHz)
・ Burst signal frequency: 18 MHz
OFDM symbol time: 17.5 μsec (1575 clock at 90 MHz)
-Variable time range of frame adjustment signal: 0 to 111 nsec (0 to 10 clocks at 90 MHz)
The time length of the frame adjustment signal is 55.5 nsec (5 clocks at 90 MHz) when the adjustment time information output from the adjustment time determination unit 112 is 0, and the time length changes according to the adjustment time information.

  The timing of the internal signal of the controller 210 for each operation mode will be described with reference to FIGS. FIG. 6 is a diagram illustrating timings of the initial setting mode and the synchronization holding mode. FIG. 7 is a diagram showing timings in the player A playback mode and the player B playback mode. FIG. 8 is a diagram showing a transition from the synchronization holding mode to the player A playback mode. Further, FIG. 9 is a diagram showing a transition from the player A playback mode to the player B playback mode.

  First, in the initial setting mode and the synchronization holding mode, an operation based on the outputs of the players 200 and 201 is not performed, and a 48-kHz data frame generated based on the 90 MHz clock output from the clock signal generation unit 115 is transmitted. .

  In FIG. 6, reference numeral 601 denotes a clock signal having a frequency of 90 MHz generated by the clock signal generator 115. Reference numeral 602 denotes an output signal of the operation mode selection unit 104, which is set to the initial setting mode or the synchronization holding mode. Reference numeral 603 denotes a clock signal output from the clock selector 103, and no signal is output in the initial setting mode or the synchronization holding mode. Reference numeral 604 denotes a clock signal output from the frame clock generator 113.

  Since the adjustment time information output from the adjustment time determination unit 112 is 0, the frame clock generation unit 113 divides the 90 MHz clock signal input from the clock signal generation unit 115 and generates a 48 kHz clock signal. Is output.

  Reference numeral 605 denotes a phase difference count value output from the phase comparator 111. When the operation mode is the initial setting mode or the synchronization holding mode, 0 is always output as the phase difference count value. Reference numeral 606 denotes adjustment time information output from the adjustment time determination unit 112. Since the phase difference count value is 0, 0 is also output as the adjustment time information.

  Reference numeral 607 denotes a data frame output from the data frame generation unit 106. The data frame generation unit 106 generates a data frame in which setting data and adjustment time information are arranged in the initial setting mode, and generates a data frame in which null data and adjustment time information are arranged in the synchronization holding mode.

  Reference numeral 608 denotes an enable signal output from the timing signal generator 114. The enable signal holds an H level for a time that is the sum of the OFDM symbol and the frame adjustment signal after a predetermined time (Δd) has elapsed since the rising edge of the clock signal output from the frame clock generation unit 113. The time length of the frame adjustment signal is always 55.5 nsec (corresponding to 5 points at 90 MHz) because the output count value of the phase comparison unit 111 is 0 in the initial setting mode and the synchronization holding mode. Therefore, the H level time of the enable signal is 17.555 μsec (corresponding to 1580 points at 90 MHz).

  Reference numeral 609 denotes an OFDM passband signal to which a frame adjustment signal output from the D / A converter 110 is added. Reference numeral 610 denotes a burst signal output from the burst signal generation unit 116, which is an 18 MHz clock signal generated by dividing the 90 MHz clock signal input from the clock signal generation unit 115.

  Reference numeral 611 denotes a frame signal output from the BPF 118 to the transmission path. The sum of the OFDM symbol time, burst signal time, and frame adjustment signal time is 17.5 μsec + 3.28 μsec + 55.5 nsec = 20.83 μsec (48 kHz).

  Next, the operation of the controller 210 in the player A playback mode and the player B playback mode will be described with reference to FIG. In the player A playback mode and player B playback mode, a signal having a frame length corresponding to the input period of acoustic data having temporal fluctuation is generated and transmitted.

  In FIG. 7, reference numeral 701 denotes a clock signal having a frequency generated by the clock signal generation unit 115 of 90 MHz. A signal 702 is output from the operation mode selection unit 104, and is set to the player A playback mode or the player B playback mode. A reproduction synchronization signal 703 is output from the clock selector 103 and has temporal fluctuations. Reference numeral 704 denotes a clock signal generated by the frame clock generation unit 113. The frame clock generation unit 113 generates a clock signal whose rising point is changed based on the adjustment time information, and outputs a clock signal that substantially matches the period of the reproduction synchronization signal.

  Reference numeral 705 denotes a phase difference count value output from the phase comparator 111. The phase comparison unit 111 outputs a value obtained by counting the rise time difference between the reproduction synchronization signal and the clock signal output from the frame clock generation unit 113 by the clock signal of the clock signal generation unit 115.

  Reference numeral 706 denotes adjustment time information output from the adjustment time determination unit 112. The adjustment time determination unit 112 outputs 5 or -5 when the phase difference count value exceeds ± 5, which is the upper and lower limit value. When the phase count value is within ± 5, the adjustment time determination unit 112 adjusts the phase count value. Output as information.

  Reference numeral 707 denotes a data frame output from the data frame generation unit 106. The data frame generation unit 106 generates a data frame in which the acoustic data output from the data selector 102 and the adjustment time information output from the adjustment time determination unit 112 are arranged. Reference numeral 708 denotes an enable signal output from the timing signal generator 114. In the player A playback mode or the player B playback mode, the enable signal holds the time H level according to the adjustment time information output from the adjustment time determination unit 112.

  Reference numeral 709 denotes an OFDM passband signal to which a frame adjustment signal output from the D / A converter 110 is added. Reference numeral 710 denotes a burst signal output from the burst signal generation unit 116, which is an 18 MHz clock signal obtained by dividing the 90 MHz clock signal input from the clock signal generation unit 115 by five.

  Reference numeral 711 denotes a frame signal output from the BPF 118 to the transmission path. The sum of the OFDM symbol time, burst signal time and frame adjustment signal time is 17.5 μsec + 3.28 μsec + 0 to 111 nsec = 20.78 to 20.88 μsec. That is, when the input period of the acoustic data fluctuates within 20.78 to 20.88 μsec, frame transmission is performed in synchronization with the input timing of the acoustic data in a form including the fluctuation. For this reason, it is possible to transmit the acoustic data without causing an overflow or underflow of the buffer memory due to time fluctuation of the input period of the acoustic data.

  Next, the operation of the controller 210 when the synchronization holding mode is switched to the player A playback mode or the player B playback mode will be described with reference to FIG. At the time of switching, the phase of the reproduction synchronization signal output from the clock selector 103 is random. At this time, the controller 210 promptly synchronizes with the input timing of the acoustic data by continuing the transmission while changing the time length of the frame adjustment signal to the maximum within the variable range. By this operation, the operation mode is switched without any sound interruption.

  In FIG. 8, reference numeral 801 denotes a clock signal generated by the clock signal generation unit 115 with a frequency of 90 MHz. Reference numeral 802 denotes a signal output from the operation mode selection unit 104, and shows a case where switching from the synchronization holding mode to the player A playback mode or the player B playback mode is performed.

  A reproduction synchronization signal 803 is output from the clock selector 103. When the operation mode is the synchronization hold mode, no signal is output, and when the operation mode is the player A playback mode and the player B playback mode, a playback synchronization signal having a temporal fluctuation is output.

  Reference numeral 804 denotes a clock signal generated by the frame clock generation unit 113. The frame clock generation unit 113 generates a clock signal whose rising point is changed based on the adjustment time information. Reference numeral 805 denotes a phase difference count value output from the phase comparator 111. The phase comparator 111 outputs a value obtained by counting the rise time difference between the reproduction synchronization signal and the clock signal output from the frame clock generator 113 by the clock of the clock signal generator 115.

  Reference numeral 806 denotes adjustment time information output from the adjustment time determination unit 112. The adjustment time determination unit 112 outputs 5 or -5 when the phase difference count value exceeds ± 5, which is the upper and lower limit value. When the phase count value is within ± 5, the adjustment time determination unit 112 adjusts the phase count value to the adjustment time. Output as information. Reference numeral 807 denotes a data frame output from the data frame generation unit 106. Reference numeral 808 denotes an enable signal output from the timing signal generator 114. Reference numeral 809 denotes an OFDM passband signal to which a frame adjustment signal output from the D / A converter 110 is added.

  A burst signal 810 is output from the burst signal generation unit 116 and is an 18 MHz clock signal obtained by dividing the 90 MHz clock signal input from the clock signal generation unit 115 by five. Reference numeral 811 denotes a frame signal output from the BPF 118 to the transmission line.

  Next, the operation of the controller 210 when the player A playback mode is switched to the player B playback mode will be described with reference to FIG.

  At the time of this switching, the phase of the reproduction synchronization signal output from the clock selector 103 is random, and the operation is similar to that at the time of switching from the synchronization holding mode to the player A reproduction mode or the player B reproduction mode shown in FIG. It will be a thing.

  In FIG. 9, reference numeral 901 denotes a clock signal generated by the clock signal generation unit 115 with a frequency of 90 MHz. A signal 902 is output from the operation mode selection unit 104, and shows a case where the player A playback mode is switched to the player B playback mode.

  A reproduction synchronization signal 903 is output from the clock selector 103. When switching from the player A playback mode to the player B playback mode, a playback synchronization signal having a random phase is output. Reference numeral 904 denotes a clock signal generated by the frame clock generation unit 113.

  Reference numeral 905 denotes a phase difference count value output from the phase comparator 111. Reference numeral 906 denotes adjustment time information output from the adjustment time determination unit 112. The adjustment time determination unit 112 outputs 5 or -5 when the phase difference count value exceeds ± 5, which is the upper and lower limit value. When the phase count value is within ± 5, the adjustment time determination unit 112 adjusts the phase count value to the adjustment time. Output as information.

  Reference numeral 907 denotes a data frame output from the data frame generation unit 106. Reference numeral 908 denotes an enable signal output from the timing signal generator 114. Reference numeral 909 denotes an OFDM passband signal to which a frame adjustment signal output from the D / A converter 110 is added.

  Reference numeral 910 denotes a burst signal output from the burst signal generator 116, which is an 18 MHz clock signal obtained by dividing the 90 MHz clock signal input from the clock signal generator 115 by five. Reference numeral 911 denotes a frame signal output from the BPF 118 to the transmission path.

  As shown in FIGS. 8 and 9, when the operation mode is switched, the controller 210 continues the transmission while changing the time length of the frame adjustment signal to the maximum within the variable range. This promptly synchronizes with the input timing of the acoustic data, and the operation mode is switched without interruption of sound.

  Next, the configuration and operation of the adapters 220 to 225 will be described with reference to FIGS. 10 and 11. In addition, since the structures of the adapters 220 to 225 are the same, only the adapter will be described here.

  FIG. 10 is a block diagram illustrating an example of the configuration of the adapter in the present embodiment. FIG. 11 is a diagram showing the input / output and internal signal timing of the adapter in this embodiment.

  In FIG. 10, the received signal is input to the A / D conversion unit 1000 and the PLL unit 1001 via the signal line 1050. The A / D converter 1000 performs A / D conversion on the received signal, and outputs the digitized received signal to the orthogonal demodulator 1002 and the gate signal generator 1003 via the signal line 1051.

  The gate signal generation unit 1003 detects a burst signal based on the output of the A / D conversion unit 1000, and generates a gate signal that is at an H level for an arbitrary time within the burst signal interval. The gate signal is output to the PLL unit 1001 through the signal line 1052.

  The PLL unit 1001 extracts a burst signal from a transmission signal output from the controller 210 or an adapter connected upstream using the gate signal input from the gate signal generation unit 1003 as a window signal. The PLL unit 1001 generates a clock signal by multiplying a burst signal by a phase lock loop (PLL), and sends it to a timing signal generation unit 1004, a burst signal generation unit 1005, and a D / A conversion unit 1010 via a signal line 1053. Output.

  The burst signal generation unit 1005 divides the clock signal input from the PLL unit 1001 to generate a transmission / reception clock synchronization signal and outputs the signal to the output signal selector 1011 via the signal line 1054.

  The orthogonal demodulation unit 1002 generates a complex OFDM baseband signal by performing orthogonal demodulation on the digital signal input from the A / D conversion unit 1000, and outputs the complex OFDM baseband signal to the OFDM demodulation unit 1006 via the signal line 1055.

  The OFDM demodulator 1006 generates a data frame by performing OFDM demodulation on the complex OFDM baseband signal. The OFDM demodulator 1006 adjusts the symbol timing of the next frame using the adjustment time information arranged in the data frame. That is, the demodulation process is performed at the correct timing by controlling the timing of opening the FFT window of the next frame based on the adjustment time information. The generated data frame is output to the output unit 1013 and the OFDM modulation unit 1007 via the signal line 1056. The adjustment time information in the data frame is output to the timing signal generation unit 1004 and the frame adjustment signal addition unit 1009 via the signal line 1057.

  The timing signal generation unit 1004 operates based on the clock signal input from the PLL unit 1001 and the adjustment time information output from the OFDM demodulation unit 1006. Then, an enable signal having a time H level that is the sum of the OFDM symbol time and the frame adjustment signal time is generated. The enable signal is output to the D / A converter 1010, the output signal selector 1011, and the output unit 1013 through the signal line 1058. In the adapters 220 to 225, the enable signal is also used as a reproduction synchronization signal.

  The OFDM modulation unit 1007 performs OFDM modulation on the data frame input from the OFDM demodulation unit 1006 to generate a complex OFDM baseband signal. The generated complex OFDM baseband signal is output to the quadrature modulation unit via a signal line 1059.

  The orthogonal modulation unit 1008 generates an OFDM passband signal by performing orthogonal modulation on the complex OFDM baseband signal input from the OFDM modulation unit 1007, and outputs the OFDM passband signal to the frame adjustment signal addition unit 1009 via the signal line 1060.

  Frame adjustment signal adding section 1009 generates a frame adjustment signal having a length corresponding to the adjustment time information input from OFDM demodulation section 1006, and adds the frame adjustment signal to the OFDM passband signal. The OFDM passband signal to which the frame adjustment signal is added is output to the D / A converter 1010 via the signal line 1061.

  The D / A conversion unit 1010 D / A converts the output of the frame adjustment signal addition unit 1009 based on the clock signal input from the PLL unit 1001 at the rise of the enable signal input from the timing signal generation unit 1004. The analog signal output from the D / A converter 110 is output to the output signal selector 1011 via the signal line 1062.

  The output signal selector 1011 operates based on the enable signal input from the timing signal generation unit 1004, selects the output of the D / A conversion unit 1010 when it is at the H level, and outputs it to the BPF 1012 via the signal line 1063. When the enable signal is at L level, the output of the burst signal generation unit 1005 is selected and output to the BPF 1012.

  The BPF 1012 is a bandpass filter for band limitation. The signal that has passed through the BPF 1012 is output to the transmission line via the signal line 1064.

  The output unit 1013 extracts the sound data and setting data of the own channel from the data frame input from the OFDM demodulator 1006. In the initial setting mode, the delay time adjustment and volume adjustment of the speaker output are performed based on the extracted setting data. In the player A playback mode and the player B playback mode, the extracted acoustic data is output to the speaker based on the enable signal input from the timing signal generation unit 1004, so that a correct acoustic output is obtained.

  As a result of the operation of each of these parts, regardless of the operation mode, the adapter receives signals received from the controller 210 or the adapter connected upstream and the signals having the same frame period and the same configuration including fluctuations thereof downstream. Send to connected adapter.

  The adapters 220 to 225 perform a uniform operation regardless of the operation mode. FIG. 11 is a diagram illustrating input / output and internal signal timings of the adapters 220 to 225 in the player A playback mode.

  In FIG. 11, reference numeral 1101 denotes a received signal from the controller 210 output from the A / D converter 1000 or an adapter connected upstream, and the time length of each frame includes fluctuations. Reference numeral 1102 denotes a gate signal output from the gate signal generation unit 1003. The gate signal generation unit 1003 detects a burst signal from the reception signal output from the A / D conversion unit 1000, and outputs a gate signal that is at an H level for an arbitrary time within the burst signal interval.

  Reference numeral 1103 denotes a clock signal output from the PLL unit 1001. The PLL unit 1001 multiplies the burst signal by 5 and outputs a 90 MHz clock signal. Reference numeral 1104 denotes a data frame output from the OFDM demodulator 1006. The OFDM demodulator 1006 performs demodulation processing at the correct timing by controlling the symbol timing of the next frame based on the adjustment time information in the data frame.

  Reference numeral 1105 denotes an enable signal output from the timing signal generator 1004. The enable signal is used by the output signal selector 1011 to switch the output between the OFDM passband signal and the burst signal, and is also used as an output timing signal to the speaker by the output unit 1013.

  A burst signal 1106 is output from the burst signal generation unit 1005. Reference numeral 1107 denotes a transmission frame output from the BPF 1012 to the transmission path.

  As shown in FIG. 11, the adapter transmits a signal having the same frame period and the same structure including the received signal received from the controller 210 or the adapter connected upstream and the fluctuation thereof to the adapter connected downstream. To do.

  According to the present embodiment, when data input at a constant cycle is transmitted in a continuous frame having a predetermined configuration, a malfunction such as sound interruption occurs even when the operation changes such as switching of an external device. Switching can be performed without any problem.

  In addition, even when a low-capacity buffer memory is used, it is possible to guarantee a stable operation that does not cause an overflow or underflow of the buffer memory.

  In this embodiment, the case where acoustic data is transmitted has been described as an example. However, the present invention is not limited to this, and is particularly useful for streaming transmission of large-capacity data such as high-definition video data.

  Since this embodiment includes a burst signal in a frame, this embodiment is useful when it is necessary to synchronize the operation clock and the frequency required for modulation / demodulation processing between the transmitting and receiving apparatuses.

  Further, in the present embodiment, a portion not including significant data is provided separately from the portion including significant data in data transmission, and the length thereof is increased or decreased. Therefore, when the portion including significant data is a fixed length Useful for.

  Therefore, for example, as in the OFDM modulation / demodulation method, the frequency of modulation / demodulation processing needs to be synchronized between the transmitting and receiving apparatuses, and the length of the portion (significant symbol in the case of the OFDM modulation / demodulation method) containing significant data is fixed It is suitable when it is long.

  Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copier, a facsimile machine, etc.) composed of a single device. It may be applied.

  In addition, a recording medium in which a program code of software for realizing the functions of the above-described embodiments is recorded is supplied to the system or apparatus, and the computer (CPU or MPU) of the system or apparatus stores the program code stored in the recording medium. Read and execute. It goes without saying that the object of the present invention can also be achieved by this.

  In this case, the program code itself read from the computer-readable recording medium realizes the functions of the above-described embodiments, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the following cases are included. That is, based on the instruction of the program code, an OS (operating system) running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. .

  Further, the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. After that, based on the instruction of the program code, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing, and the function of the above-described embodiment is realized by the processing. Needless to say.

It is a block diagram which shows an example of a structure of the controller 210 in this embodiment. It is a block diagram which shows the structural example of the 5.1 channel sound system in this embodiment. It is a figure which shows an example of the state transition of the 5.1 channel sound system in this embodiment. It is a figure which shows an example of a structure of the flame | frame transmitted in this embodiment. It is a figure which shows an example of a structure of the data frame in this embodiment. It is a figure which shows the timing of initial setting mode and a synchronous holding | maintenance mode. It is a figure which shows the timing of the player A reproduction mode and the player B reproduction mode. It is a figure which shows the transition from the synchronization holding | maintenance mode to the player A reproduction mode. It is a figure which shows the transition from the player A reproduction mode to the player B reproduction mode. It is a block diagram which shows an example of a structure of the adapter in this embodiment. It is a figure which shows the input / output and internal signal timing of the adapter in this embodiment.

Explanation of symbols

100 Multi-channel acoustic decoder A
101 Multi-channel acoustic decoder B
102 data selector 103 clock selector 104 operation mode selection unit 105 transmission data generation unit 106 data frame generation unit 107 OFDM modulation unit 109 orthogonal modulation unit 110 frame adjustment signal addition unit 111 phase comparison unit 112 adjustment time determination unit 113 frame clock generation unit 114 Timing signal generator 115 Clock signal generator 116 Burst signal generator 117 Output signal selector

Claims (8)

A transmission method executed by a transmission apparatus that transmits a transmission frame composed of a variable length part and a fixed length part,
Means for generating a reproduction synchronization signal, from a data input from an external device , generating a reproduction synchronization signal having a period corresponding to a sampling period of the input data;
Means for generating a clock signal, generating a clock signal having a period corresponding to a sampling period of data input from the external device;
A detection step of detecting means, caused by the switching of the operation mode, a signal the reproduction synchronization, detects the phase difference between the clock signal,
Frame generation means, a frame generating step of generating a transmission frame by changing the length of the variable portion in accordance with a phase difference the detection,
A transmission step of transmitting the generated transmission frame to the receiving device in synchronization with a cycle of the clock signal;
A transmission method characterized by comprising: Wherein in the detection step, the first mode of operation to transmit a transmission frame consisting of the variable portion and the transmitting the fixed length portion generated based on the data generated in the interior of the device, and the variable length portion the resulting by switching from the external device to the second mode of operation to transmit a transmission frame composed of the fixed-length portion which is generated on the basis of the input data, the phase difference between the clock signal and the reproduction synchronization signal The transmission method according to claim 1, wherein:   2. The transmission method according to claim 1, wherein the operation mode is switched by changing an external device for inputting data.   The transmission method according to any one of claims 1 to 3, wherein, in the frame generation step, the length of the variable length portion is changed within a predetermined range.   The transmission apparatus which performs the transmission method of any one of Claims 1 thru | or 4.   6. A communication system comprising: the transmission device according to claim 5; and a reception device that receives a transmission frame transmitted from the transmission device.   The program for making a computer perform the transmission method of any one of Claims 1 thru | or 4. The operation is switched between a first operation mode for transmitting a transmission frame generated from data input from an external device and a second operation mode for transmitting a transmission frame generated from data generated inside the transmission device. A transmission device capable of
A decoder that decodes multi-channel acoustic data including reproduction synchronization data input from the external device, and generates acoustic data and a reproduction synchronization signal;
Command data related to system settings, or a transmission data generation unit that generates null data,
In the case of the first operation mode, a data selector that outputs the acoustic data generated by the decoder; in the case of the second operation mode, a data selector that outputs the data generated by the transmission data generation unit;
A clock selector for outputting a reproduction synchronization signal generated by the decoder in the case of the first operation mode, and a control for not outputting a signal in the case of the second operation mode;
A clock generation unit that generates a clock signal having a period corresponding to the period of the reproduction synchronization signal;
In the case of the first operation mode, phase difference information between the reproduction synchronization signal generated by the decoder and the clock signal generated by the clock generation unit is output. In the case of the second operation mode, An output unit for outputting predetermined phase difference information;
An adjustment time determination unit that generates adjustment time information based on the output of the output unit;
A data frame generation unit that generates a data frame based on the output of the data selector and the adjustment time information generated by the adjustment time determination unit;
A generator for generating an OFDM symbol from the data frame generated by the data frame generator;
A burst signal generator for generating a burst signal;
Generating means for generating a transmission frame comprising the burst signal, the OFDM symbol, and a frame adjustment signal having a length corresponding to the adjustment time information;
Transmitting means for transmitting the transmission frame in synchronization with a cycle of the clock signal generated by the clock signal generation unit;
A transmission device comprising:

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