JP2012039260A - Transmission and reception system, transmitter, and receiver - Google Patents

Abstract

In a transmission / reception system in a digital interface for video / audio transmission, it is possible to transmit audio data with high sound quality and without interruption of sound when content is switched.
A received audio clock generator generates a plurality of audio clocks RAC1 and RAC2 based on a reference clock RCLK, and an audio clock information generator 115 generates audio clock information IAC including frequency information of the audio clock RAC1. Generate. The audio clock reproduction unit 105 reproduces the audio clock TAC1 having the frequency indicated by the audio clock information IAC, and the transmission audio clock generation unit 106 generates a plurality of audio clocks TAC1 and TAC2 based on the audio clock TAC1. In data transmission, the transmission audio clock generation unit 106 selects the transmission audio clock TAC according to the sampling frequency information of the transmission audio data, and the reception audio clock generation unit 116 receives the reception audio clock according to the sampling frequency information separated from the transmission data. Select RAC.
[Selection] Figure 1

Description

  The present invention relates to a transmission / reception system used for high-speed transmission of video data and audio data.

  An HDMI (High-Definition Multimedia Interface) standard is known as an interface standard for transmitting digitized video / audio data at high speed. In a transmission line compliant with the HDMI standard, frequency division parameters M and N for connecting a pixel clock synchronized with video data and an audio clock are obtained, and the frequency division parameters M and N are transmitted in place of the audio clock.

  FIG. 4 is a block diagram showing a configuration example of a conventional transmission / reception system. In FIG. 4, a transmission device 401 and a reception device 402 are connected to each other via a transmission line that conforms to the HDMI standard. The transmission device 401 multiplexes audio data with video data and transmits the multiplexed audio data to the reception device 402. Examples of the transmission device 401 include a DVD player and a BD (Blue-ray Disc) recorder, and examples of the reception device 402 include a plasma television and a liquid crystal television.

  FIG. 5 is a diagram for explaining the relationship between the audio clock and pixel clock and the frequency division parameters M and N. The frequency f of the audio clock is often set to an integer multiple of the sampling frequency fs when digitizing the audio signal that was originally an analog signal. In FIG. 5, 128 times the sampling frequency fs is set as the frequency f of the audio clock. Specifically, when fs = 48 kHz, f = 128 × fs = 6.144 MHz.

The frequency division parameter N is a parameter for dividing the audio clock, and the frequency division parameter M is a parameter for dividing the pixel clock. The following relationship exists among the frequency f of the audio clock, the frequency pclk of the pixel clock, and the frequency division parameters M and N.
pclk / M = f / N
In order to obtain such frequency division parameters M and N, for example, N may be a predetermined value, and M may be the result of counting the N frequency division of the audio clock with the pixel clock. For example, when pclk = 27 MHz and f = 6.144 MHz, if N = 6144 is set, M = 27000 is obtained. In the transmission device 401, the audio clock is divided by N by the frequency divider 102, and the counter 103 counts it by the pixel clock to obtain M.

  The frequency division parameters M and N thus obtained are packetized by the video / audio / packet multiplexing unit 104 and multiplexed during the blanking period of the video data. The video / audio / packet multiplexing unit 104 packetizes the audio data in the same manner and multiplexes it during the blanking period of the video data.

  The video / audio / packet multiplexed data and the pixel clock output from the transmission device 401 are transmitted via the transmission path and received by the reception device 402. In the receiving apparatus 402, the video / audio / packet separating unit 114 separates and outputs the video data and the pixel clock. The video data is synchronized with the pixel clock, and is generally displayed on a plasma panel or a liquid crystal panel after image processing for improving image quality is performed later.

The video / audio / packet separation unit 114 separates and outputs the frequency division parameters M and N.
f = (pclk / M) × N
Therefore, if the pixel clock is divided by M by the frequency divider 112 and the output of the frequency divider 112 is multiplied by N by the multiplier 113, the audio clock having the frequency f can be reproduced.

  In this way, on the transmission line compliant with the HDMI standard, the audio clock is transmitted using the frequency division parameters M and N. However, the audio clock reproduced by the receiving apparatus 402 includes jitter due to jitter superimposed on the pixel clock on the transmission path. For this reason, sound quality will deteriorate rather than the time of transmission.

  Patent Document 1 discloses a configuration for transmitting audio data with higher sound quality. FIG. 6 shows a configuration disclosed in Patent Document 1. The configuration of FIG. 6 is different from FIG. 4 in that the receiving device 602 side has an audio clock reference. First, the transmission device 601 transmits the frequency division parameter N to the reception device 602. In the receiving device 602, the frequency divider 221 divides the master clock by N, and the period counter 222 counts the output of the frequency divider 221 with the received pixel clock. The count value M is transmitted from the reception device 602 to the transmission device 601 using, for example, CEC (Consumer Electronics Control). CEC is a protocol for transmitting and receiving device control signals such as commands according to remote control operations, for example. In the HDMI standard, mutual communication by CEC is defined as an option.

  In the transmitter 601, the frequency divider 223 divides the video clock by M, and the multiplier 224 multiplies the output of the frequency divider 223 by N. As a result, an audio clock having the same frequency as the master clock can be reproduced. Then, the transmission device 601 transmits audio data synchronized with the reproduced audio clock. The receiving device 611 receives audio data and reproduces audio using a high-precision master clock. As a result, high sound quality can be achieved.

JP 2009-38596 A (FIG. 5)

  Various sampling frequencies are used for audio signals. For example, 44.1 kHz is used in a compact disc (CD), but 48 kHz is used in digital broadcasting. In order to achieve higher sound quality, integers such as 176.4 kHz and 192 kHz are used. In recent years, since recording on a medium such as a CD-R can be easily performed by a personal computer or the like, a plurality of contents having different sampling frequencies may be recorded on one medium. When reproducing such media, the sampling frequency of the audio signal changes every time the content changes. That is, the sampling frequency changes frequently.

  However, in the conventional transmission / reception system, when the sampling frequency of the audio signal is switched, there is a problem that the sound is not output immediately and the sound is easily cut off.

  For example, in the configuration of FIG. 6, when the sampling frequency is switched, information on the sampling frequency is transmitted from the transmitting device 601 to the receiving device 611 in, for example, packetized form. The receiving device 611 reads the sampling frequency from the received packet and switches the audio clock to one corresponding to this sampling frequency. Thereafter, M is obtained by the operation of the frequency divider 221 and the period counter 213, and is transmitted to the transmission device 601. Then, a new audio clock is reproduced by the frequency divider 223 and the multiplier 224 in the transmission device 601.

  That is, in the conventional transmission / reception system, when the sampling frequency is switched, it takes a long time from the start of switching until the audio clock is reproduced in the transmission apparatus 601. In particular, the multiplier 224 takes a PLL (Phase Locked Loop) configuration, and thus requires a long time until locking. This leads to a problem that sound is not output for a short time immediately after the content is switched, and sound is cut off.

  In view of the above problems, the present invention enables transmission of audio data with high sound quality and no interruption of sound when switching contents in a transmission / reception system in a digital interface for video / audio transmission. With the goal.

  One aspect of the present invention is a transmission / reception system including a transmission device and a reception device in a digital interface for video / audio transmission. The reception device receives transmission data output from the transmission device, and receives the transmission data from the transmission data. , Based on the received video data, the received video clock, the received audio data, the video / audio / packet separating unit that separates the sampling frequency information of the received audio data, and the reference clock given from the outside Generate a plurality of audio clocks, and select and output one audio clock as a reception audio clock from the plurality of audio clocks according to the sampling frequency information of the received audio data. And the reception audio clock output by the reception audio clock generation unit, A reception audio processing unit that outputs reception audio data, and a first audio clock that is one of a plurality of audio clocks generated by the reception audio clock generation unit, and at least information on the frequency of the first audio clock. An audio clock information generating unit that generates audio clock information including the audio clock information and outputs the audio clock information to the transmission device. The transmission device receives the audio clock information output from the reception device, and receives the audio clock information. And generating a plurality of audio clocks having different frequencies based on the second audio clock, and generating a plurality of audio clocks based on the second audio clock. In accordance with the sampling frequency information of the transmission audio data, one audio clock is selected as the transmission audio clock and output. By packetizing the audio clock generation unit, the transmission audio data synchronized with the transmission audio clock, and the sampling frequency information of the transmission audio data, and superimposing them on the blanking period of the transmission video data synchronized with the transmission video clock And a video / audio / packet multiplexing unit for generating the transmission data.

  According to this aspect, in the receiving device, the reception audio clock generation unit generates a plurality of audio clocks having different frequencies based on the reference clock given from the outside. The audio clock information generation unit generates audio clock information including frequency information of the first audio clock that is one of the plurality of audio clocks, and outputs the audio clock information to the transmission device. In the transmission device, the audio clock reproduction unit reproduces a second audio clock having a frequency indicated by the audio clock information output from the reception device. Then, the transmission audio clock generation unit generates a plurality of audio clocks having different frequencies based on the second audio clock. That is, a plurality of audio clocks having different frequencies are prepared in advance in the receiving device and the transmitting device. In data transmission, the transmission audio clock generation unit in the transmission device selects a transmission audio clock from a plurality of audio clocks according to the sampling frequency information of the transmission audio data, and the reception audio clock generation unit in the reception device transmits A reception audio clock is selected from a plurality of audio clocks according to the sampling frequency information of the reception audio data separated from the data.

  As a result, even when the sampling frequency is switched at the time of content switching, the new transmission audio clock and reception audio clock can be used quickly in the transmission device and the reception device. Therefore, sound interruption does not occur when switching contents. In addition, since the reception audio clock is generated based on a reference clock given from the outside, the accuracy is high, so that the sound quality of the audio signal to be reproduced is not deteriorated.

  According to another aspect of the present invention, as a transmission device in a digital interface for video / audio transmission, audio clock information including at least frequency information of a first audio clock output from a reception device is received and the audio is transmitted. An audio clock reproduction unit that reproduces a second audio clock having a frequency indicated by the clock information, and a plurality of audio clocks having different frequencies based on the second audio clock are generated. From, according to the sampling frequency information of the transmission audio data, a transmission audio clock generation unit that selects and outputs one audio clock as the transmission audio clock, the transmission audio data synchronized with the transmission audio clock, and the sampling frequency Packetized information and blanking of transmission video data synchronized with the transmission video clock By superimposing in a period, in which a video-audio packet multiplexing unit for generating transmission data.

  Further, in another aspect of the present invention, as a receiving device in the digital interface for video / audio transmission, the transmission data output from the transmitting device is received, and from this transmission data, the received video data, the received video clock, Based on a video / audio / packet separating unit that separates received audio data and sampling frequency information of the received audio data, and a reference clock given from the outside, a plurality of audio clocks having different frequencies are generated, A reception audio clock generation unit that selects and outputs one audio clock as a reception audio clock from the plurality of audio clocks according to the sampling frequency information, and a reception audio clock output from the reception audio clock generation unit In synchronization with the received voice processing unit for outputting the received voice data, and the received voice clock. An audio clock that generates audio clock information including at least information on the frequency of the first audio clock from a first audio clock that is one of a plurality of audio clocks generated in the generation unit, and outputs the audio clock information to the transmission device And an information generation unit.

  According to the present invention, deterioration in sound quality of an audio signal reproduced on the receiving device side is suppressed, and a new transmission audio clock and reception audio clock can be quickly used even when the sampling frequency is changed. In addition, it is possible to transmit audio data so that no sound interruption occurs at the time of content switching.

It is a block diagram which shows the structure of the transmission / reception system which concerns on embodiment. FIG. 2 is a block diagram illustrating a configuration example in which the configuration of FIG. 1 is embodied. It is a block diagram which shows the other structural example which actualized the structure of FIG. It is a block diagram which shows the structural example of the conventional transmission / reception system. It is a figure which shows the relationship between an audio | voice clock and a pixel clock, and a frequency division parameter. It is a block diagram which shows the structural example of the conventional transmission / reception system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the transmission / reception system shown in the present embodiment, it is assumed that a transmission device and a reception device are connected to each other via a transmission line that conforms to the HDMI standard. However, the application range of the present invention is not limited to HDMI as a digital interface for video / audio transmission, but can be applied to other digital interfaces.

  FIG. 1 is a block diagram illustrating a configuration of a transmission / reception system according to the embodiment. 1 includes a frequency divider 102, a counter 103, a video / audio / packet multiplexing unit 104, an audio clock reproduction unit 105, and a transmission audio clock generation unit 106. The transmission audio clock generation unit 106 includes a frequency divider / multiplier 107 and a selector 108. The reception device 111 includes a frequency divider 112, a multiplier 113, a video / audio / packet separation unit 114, an audio clock information generation unit 115, a reception audio clock generation unit 116, and a buffer 119. . The reception audio clock generation unit 116 includes a frequency divider / multiplier 117 and a selector 118.

  In the configuration of FIG. 1, a high-accuracy reference clock RCLK is input to the receiving device 111 from the outside. The reception audio clock generation unit 116 generates a plurality of audio clocks having different frequencies from each other based on the reference clock RCLK given from the outside. For example, as shown in FIG. 1, two audio clocks are generated: an audio clock RAC1 having a frequency of 128fs1 which is 128 times the sampling frequency fs1, and an audio clock RAC2 having a frequency of 128fs2 which is 128 times the sampling frequency fs2. Is done. Such an audio clock is obtained, for example, by dividing or multiplying the reference clock RCLK by the frequency divider / multiplier 117.

  Note that the frequency divider / multiplier 117 here does not necessarily need to have both functions of frequency division and multiplication. Depending on the frequency relationship between the reference clock RCLK and a plurality of generated audio clocks, the frequency divider / multiplier 117 may have only a frequency dividing function or only a frequency multiplying function. It may be sufficient if it has.

  The audio clock information generation unit 115 includes, from the first audio clock that is one of the plurality of audio clocks generated by the reception audio clock generation unit 116, audio clock information including at least information on the frequency of the first audio clock. An IAC is generated and output to the transmission apparatus 101. For example, in the configuration of FIG. 1, the audio clock information IAC including information of the frequency 128 fs1 is generated from the audio clock RAC1 as the first audio clock.

  In the transmission apparatus 101, the audio clock reproduction unit 105 receives the audio clock information IAC output from the reception apparatus 111, and reproduces a second audio clock having a frequency indicated by the audio clock information IAC. For example, in the configuration of FIG. 1, the audio clock reproduction unit 105 reproduces the audio clock TAC1 as the second audio clock having the frequency 128fs1 indicated by the audio clock information IAC.

  The transmission audio clock generation unit 106 generates a plurality of audio clocks having different frequencies, including the second audio clock, based on the second audio clock reproduced by the audio clock reproduction unit 105. For example, in the configuration of FIG. 1, the transmission audio clock generation unit 106 divides the audio clock TAC1 by fs1 by the frequency divider / multiplier 107 based on the audio clock TAC1, and multiplies it by fs2 to thereby generate audio having a frequency of 128 fs2. A clock TAC2 is generated.

  In this way, by adopting a configuration in which the audio clock information IAC is sent from the reception device 111 to the transmission device 101, a plurality of audio clocks based on the reference clock RCLK given to the reception device 111 are received by the reception device 111 and the transmission device. 101 can be prepared in advance.

  In FIG. 1, only the audio clocks corresponding to the two sampling frequencies fs1 and fs2 are shown. Of course, it is possible to generate audio clocks corresponding to three or more sampling frequencies.

  Here, the plurality of audio clocks generated by the reception audio clock generation unit 116 of the reception device 111 and the plurality of audio clocks generated by the transmission audio clock generation unit 106 of the transmission device 101 have the same frequency breakdown. It is preferable. In other words, the frequency relationship between the first audio clock RAC1 to which the frequency information is transmitted by the audio clock information IAC and the plurality of audio clocks generated in the reception audio clock generation unit 116 is reproduced from the audio clock information IAC. The frequency relationship between the second audio clock TAC1 and the plurality of audio clocks generated by the transmission audio clock generation unit 106 is preferably the same.

  With respect to the configuration of FIG. 1, the video / audio data transmission operation will be described.

  In the transmission apparatus 101, the transmission audio clock generation unit 106 selects and outputs one audio clock as the transmission audio clock TAC from the plurality of audio clocks TAC1 and TAC2 according to the sampling frequency information of the audio data to be transmitted. To do. Specifically, the selector 108 selects one of the audio clocks TAC1 and TAC2 as the transmission audio clock TAC (frequency 128 fs) according to the information indicating the sampling frequency fs. In HDMI, information indicating the sampling frequency fs is stored in the data structure of audio data. Alternatively, the sampling frequency information can also be obtained from the frequency division parameters M and N.

  The audio data is input to the video / audio / packet multiplexing unit 104 in synchronization with the transmission audio clock TAC output from the transmission audio clock generation unit 106. The frequency divider 102 and the counter 103 generate frequency division parameters M and N from the transmission audio clock TAC and the pixel clock (video clock) PCLK, and send them to the video / audio / packet multiplexing unit 104. The video / audio / packet multiplexing unit 104 generates transmission data by packetizing transmission audio data synchronized with the transmission audio clock TAC and superimposing the packet on a blanking period of video data synchronized with the pixel clock PCLK. . At this time, sampling frequency information and frequency division parameters M and N are also packetized and transmitted.

  In the reception device 111, the video / audio / packet separation unit 114 receives the transmission data output from the transmission device 101, and separates the video data, the pixel clock, and the audio data from the transmission data. Also, sampling frequency information and frequency division parameters M and N are separated. The frequency divider 112 and the multiplier 113 regenerate the audio clock RAC 'from the divided frequency division parameters M and N. The received audio data is temporarily stored in a buffer 119 as a reception audio processing unit in synchronization with the reproduced audio clock RAC '.

  On the other hand, the reception audio clock generation unit 116 selects and outputs one audio clock as the reception audio clock RAC from the plurality of audio clocks RAC1 and RAC2 according to the sampling frequency information of the received audio data. Specifically, the selector 118 selects one of the audio clocks RAC1 and RAC2 as the transmission audio clock RAC (frequency 128 fs) according to the information indicating the sampling frequency fs. Since the selected reception audio clock RAC is a high-accuracy clock based on the reference clock RCLK, by using this as a read clock for the buffer 119, audio data synchronized with the high-accuracy reception audio clock RAC is received. Output from the device 111.

  As described above, according to the present embodiment, a plurality of audio clocks RAC1 and RAC2 based on the reference clock RCLK are prepared in advance in the reception device 111, and also in the transmission device 101 that has received the audio clock information IAC from the reception device 111. A plurality of audio clocks TAC1 and TAC2 are prepared in advance. In the data transmission, in the transmission device 101, the transmission audio clock generation unit 106 selects the transmission audio clock TAC from the plurality of audio clocks according to the sampling frequency information of the transmission audio data, and in the reception device 111, the reception audio clock generation. The unit 116 selects the reception audio clock RAC from the plurality of audio clocks according to the sampling frequency information of the reception audio data separated from the transmission data.

  As a result, even when the sampling frequency is switched at the time of content switching, the new transmission audio clock TAC and reception audio clock RAC can be used quickly in the transmission device 101 and the reception device 111. Therefore, sound interruption does not occur when switching contents. Further, since the reception audio clock RAC is generated based on the reference clock RCLK given from the outside, the accuracy is high, so that the sound quality of the reproduced audio signal is not deteriorated.

  In the present embodiment, the example in which the frequency division parameters M and N are transmitted / received is shown. However, the frequency division parameters M and N are not necessarily transmitted / received. This is because the audio data received by the reception device 111 is synchronized with a plurality of audio clocks generated by the reception audio clock generation unit 116, and therefore it is not necessary to reproduce the reception audio clock from the frequency division parameters M and N. . When the frequency division parameters M and N are not transmitted / received, for example, the received audio data may be written in the buffer 119 in synchronization with the pixel clock PCLK. The reception audio clock RAC output from the reception audio clock generation unit 116 is used to read out the reception audio data from the buffer 119. In the case where the frequency division parameters M and N are not transmitted / received, the frequency divider 112 and the multiplier 113 are not required in the reception device 111.

(Configuration example 1)
FIG. 2 is a block diagram showing a configuration example in which the configuration of FIG. 1 is further embodied. 2, the same reference numerals are given to the same components as those in FIG. 1, and detailed description thereof is omitted here. In the configuration of FIG. 2, the transmission device 201 includes an optical digital audio reception unit 202 as an example of the audio clock reproduction unit 105, and the reception device 211 includes an optical digital audio transmission unit 212 as an example of the audio clock information generation unit 115. It has. The transmission audio clock generation unit 106 of the transmission device 201 includes a frequency divider / multiplier 203 that divides the input clock signal by 480 and multiplies it by 441 as an example of the frequency divider / multiplier 107. As an example of the frequency divider / multiplier 117, the reception audio clock generation unit 211 211 divides the input clock signal by 441 and multiplies it by 128, and the frequency divider / multiplier 213 divides the input clock signal by 480. And a frequency divider / multiplier 214 for multiplying by 128.

  The configuration of FIG. 2 corresponds to sampling frequencies fs1 (= 48 kHz) and fs2 (= 44.1 kHz). The frequency of the reference clock RCLK given from the outside is, for example, 21.168 MHz which is a common multiple of 48 kHz and 44.1 kHz. The reception audio clock generator 116 generates an audio clock RAC1 having a frequency of 128 fs1 (= 6.144 MHz) and an audio clock RAC2 having a frequency of 128 fs2 (= 5.6448 MHz) based on the reference clock RCLK. Specifically, the frequency divider / multiplier 213 divides the reference clock RCLK by 441 and multiplies it by 128 to generate the audio clock RAC1, and the frequency divider / multiplier 214 divides the reference clock RCLK by 480 and multiplies it by 128. Thus, the audio clock RAC2 is generated.

  The optical digital audio transmission unit 212 and the optical digital audio reception unit 202 constitute a digital audio interface. As a digital audio interface, for example, the IEC60958 standard is widely used as an international standard. In the IEC 60958 standard, an audio signal is biphase-modulated and transmitted in units called frames. A synchronization pattern called a preamble is embedded at the head of each frame.

  In the present configuration example, the audio clock information IAC is transmitted from the reception device 211 to the transmission device 201 using the digital audio interface as described above. Specifically, the optical digital audio transmission unit 212 receives the audio clock RAC1 as the first audio clock from the reception audio clock generation unit 116. Then, a predetermined audio signal is bi-phase modulated in synchronization with the audio clock RAC1. Thereby, audio information in which a preamble is embedded in the same cycle as the audio clock RAC1 is generated. Further, the optical digital audio transmission unit 212 performs photoelectric conversion on the generated audio information and outputs the light. The optical digital audio reception unit 202 of the transmission apparatus 201 reversely converts the received optical signal into an electrical signal to obtain audio information. Then, by detecting the preamble from the obtained audio information, the audio clock TAC1 having the frequency 128fs1 (= 6.144 MHz) as the second audio clock is reproduced.

  Then, the transmission audio clock generation unit 106 generates an audio clock TAC2 having a frequency of 128 fs2 (= 5.6448 MHz) based on the audio clock TAC1 reproduced by the optical digital audio reception unit 202. Specifically, the frequency divider / multiplier 203 generates the audio clock TAC2 by dividing the audio clock TAC1 by 480 and multiplying it by 441.

  Since the video / audio data transmission operation is the same as that of FIG. 1, the description thereof is omitted here.

  In this configuration example, the audio information sent from the reception device 211 to the transmission device 201 may be any information that can transmit the frequency information of the audio clock RAC1 and can reproduce the audio clock TAC1 in the optical digital audio reception unit 202. Therefore, the audio information generated by the optical digital audio transmission unit 212 does not need to include a normal audio signal. That is, for example, the optical digital audio transmission unit 212 may perform modulation using a non-audio signal (constant value) or an audio signal with a predetermined period (for example, a sine wave) as the predetermined audio signal. However, if a normal audio signal is used, the transmission of the audio signal and the transmission of audio clock information can be combined.

  In this configuration example, audio information is optically transmitted from the receiving device 211 to the transmitting device 201. However, transmission of audio information is not limited to optical transmission. For example, a coaxial cable may be used. Alternatively, a signal line may be provided in the HDMI cable, and transmission may be performed using the signal line. However, it is preferable to use an existing audio interface because the cost increase can be minimized.

  In this configuration example, audio information conforming to the IEC 60958 standard as an example of a digital audio interface standard is transmitted. However, the format of the audio information to be transmitted is not limited to this. In other words, any audio signal may be used as long as it is modulated in units of frames in which a synchronization pattern is embedded and can transmit frequency information according to the period of the synchronization pattern.

(Configuration example 2)
FIG. 3 is a block diagram showing another configuration example that further embodies the configuration of FIG. 3, the same reference numerals are given to the same components as those in FIGS. 1 and 2, and the detailed description thereof is omitted here. In the configuration of FIG. 3, the transmission device 301 includes a frequency division parameter reception unit 302 as an example of the audio clock reproduction unit 105, and the reception device 311 includes a frequency division parameter transmission unit 312 as an example of the audio clock information generation unit 115. It has.

  In the configuration of FIG. 3, the reception audio clock generation unit 116 generates an audio clock RAC1 having a frequency of 128 fs1 and an audio clock RAC2 having a frequency of 128 fs2 based on the reference clock RCLK, as in the configuration of FIG. The frequency division parameter transmission unit 312 generates frequency division parameters P and Q as audio clock information from the audio clock RAC1 output from the reception audio clock generation unit 116 and the pixel clock PCLK. The frequency division parameters P and Q have the following relationship, and are generated by the same method as the frequency division parameters M and N.

PCLK / P = 128fs1 / Q
Then, the frequency division parameter transmission unit 312 transmits both or one of the frequency division parameters P and Q. For example, when a specified eigenvalue is used for Q, it is not necessary to transmit Q, and only P may be transmitted. For transmission of the frequency division parameters P and Q, for example, CEC, which is an option of the HDMI standard, may be used.

  The frequency division parameter receiving unit 302 reproduces the audio clock TAC1 from the frequency division parameter (both or one of P and Q) received from the reception device 311 and the pixel clock PCLK. For example, when Q is a predetermined fixed value, only P is received, and the audio clock TAC1 having a frequency of 128 fs1 is reproduced from the pixel clocks PCLK and P and the predetermined fixed value Q. The method of reproducing the audio clock here is the same as the method of reproducing the audio clock from the frequency division parameters M and N. Then, the transmission audio clock generation unit 106 generates an audio clock TAC2 having a frequency of 128 fs2 based on the audio clock TAC1 reproduced by the frequency division parameter reception unit 302.

  Since the video / audio data transmission operation is the same as that of FIG. 1, the description thereof is omitted here.

  In this configuration example, the CEC is used for transmission of the frequency division parameters P and Q. However, the present invention is not limited to this. For example, Ethernet or a wireless LAN may be used for transmission of the frequency division parameters P and Q.

  Note that it is desirable that the timings for transmitting the frequency division parameters P and Q coincide with the cycle determined by 128 fs1 / Q. The frequency deviation between the audio clock TAC1 output from the frequency division parameter receiving unit 302 in the transmission device 301 and the audio clock RAC1 output from the reception audio clock generation unit 116 in the reception device 311 transmits the frequency division parameters P and Q. The lower the frequency, the larger it becomes. This frequency shift may cause so-called overtaking / overtaking of the write position and the read position in the buffer 119. However, this problem may be dealt with by increasing the capacity of the buffer 119. The capacity required for the buffer 119 is such that it corresponds to the amount of audio data received during the time interval for transmitting the frequency division parameters P and Q.

  In this configuration example, the case of transmitting a set of frequency division parameters P and Q has been described. For example, a plurality of sets of frequency division parameters P and Q may be transmitted for each sampling frequency. In this case, the frequency division parameter receiving unit 302 may regenerate a plurality of audio clocks corresponding to the sampling frequency from each set of frequency division parameters P and Q.

  In the configuration examples 1 and 2 described above, fs1 = 48 kHz and fs2 = 44.1 kHz, but the sampling frequency is not limited to this. For example, if fs1 = 192 kHz and fs2 = 176.4 kHz and other sampling frequencies are obtained by dividing fs1 and fs2, a multiplier for obtaining 48 kHz to 192 kHz is not required, and the circuit is simplified. Is done.

  As described above, according to the present invention, it is possible to transmit audio data with high sound quality and no interruption of sound when switching contents in a digital interface such as HDMI. It is effective for improving data quality.

101, 201, 301 Transmission device 104 Video / audio / packet multiplexing unit 105 Audio clock reproduction unit 106 Transmission audio clock generation unit 1111, 211, 311 Reception device 114 Video / audio / packet separation unit 115 Audio clock information generation unit 116 Reception audio Clock generator 119 Buffer (Received audio processor)
202 Optical digital audio receiver (audio clock recovery unit)
212 Optical digital audio transmitter (audio clock information generator)
302 Frequency division parameter receiver (audio clock recovery unit)
312 Frequency division parameter transmission unit (audio clock information generation unit)
IAC Audio clock information PCLK Pixel clock (video clock)
RCLK reference clock RAC reception audio clock RAC1 first audio clock TAC transmission audio clock TAC1 second audio clock

Claims (14)

A transmission / reception system comprising a transmission device and a reception device in a digital interface for video / audio transmission,
The receiving device is:
Video / audio / packet that receives transmission data output from the transmission device and separates received video data, received video clock, received audio data, and sampling frequency information of the received audio data from the transmitted data A separation unit;
A plurality of audio clocks having different frequencies are generated based on a reference clock given from the outside, and one audio clock is selected from the plurality of audio clocks according to the sampling frequency information of the received audio data. A reception audio clock generator for selecting and outputting as a reception audio clock; and
A reception audio processing unit that outputs the reception audio data in synchronization with the reception audio clock output by the reception audio clock generation unit;
Audio clock information including at least information on the frequency of the first audio clock is generated from a first audio clock that is one of a plurality of audio clocks generated by the reception audio clock generation unit, and is transmitted to the transmission device. An audio clock information generator for outputting,
The transmitter is
An audio clock reproduction unit that receives the audio clock information output from the receiver and reproduces a second audio clock having a frequency indicated by the audio clock information;
A plurality of audio clocks having different frequencies are generated based on the second audio clock, and one audio clock is transmitted from the plurality of audio clocks according to sampling frequency information of transmission audio data. A transmission audio clock generator for selecting and outputting as a clock;
The transmission data is generated by packetizing the transmission audio data synchronized with the transmission audio clock and the sampling frequency information of the transmission audio data, and superimposing them in a blanking period of the transmission video data synchronized with the transmission video clock. A transmission / reception system comprising: a video / audio / packet multiplexing unit. The transmission / reception system according to claim 1,
The audio clock information generation unit of the reception device generates audio information in which a predetermined audio signal is modulated in units of frames in which a synchronization pattern is embedded in synchronization with the first audio clock, Output as audio clock information,
The audio clock reproduction unit of the transmission device reproduces the second audio clock by detecting the synchronization pattern from the audio information output as the audio clock information from the reception device. A transmission / reception system characterized by that. The transmission / reception system according to claim 2,
The transmission / reception system, wherein the predetermined audio signal is a non-audio signal or an audio signal having a predetermined period. The transmission / reception system according to claim 1,
The audio clock information generation unit of the receiving device is configured between a frequency f of the first audio clock and a frequency pclk of the received video clock.
pclk / P = f / Q
The frequency division parameters P and Q satisfying the relationship are generated, and at least one of the frequency division parameters P and Q is output as the audio clock information.
The audio clock recovery unit of the transmission device includes the second audio clock from the frequency division parameter output as the audio clock information from the reception device and the transmission video clock having the same frequency as the reception video clock. A transmission / reception system characterized by playing back a video. The transmission / reception system according to claim 4,
One of the frequency division parameters P and Q is set to a predetermined fixed value, and the other is output as the audio clock information by the audio clock information generation unit of the receiving device. A transmission device in a digital interface for video / audio transmission,
An audio clock reproduction unit that receives audio clock information that includes at least information about the frequency of the first audio clock output from the receiving device, and reproduces a second audio clock having a frequency indicated by the audio clock information;
A plurality of audio clocks having different frequencies are generated based on the second audio clock, and one audio clock is transmitted from the plurality of audio clocks according to sampling frequency information of transmission audio data. A transmission audio clock generation unit to select and output as,
The transmission audio data that is synchronized with the transmission audio clock and the sampling frequency information are packetized and superimposed on a blanking period of the transmission video data that is synchronized with the transmission video clock to generate transmission data. A transmission apparatus comprising a packet multiplexing unit. The transmission device according to claim 6, wherein
The audio clock reproduction unit modulates a predetermined audio signal output as the audio clock information from the receiving device in units of frames in which a synchronization pattern is embedded in synchronization with the first audio clock. The second audio clock is reproduced by detecting the synchronization pattern from the audio information. The transmission device according to claim 7, wherein
The transmission apparatus according to claim 1, wherein the predetermined audio signal is a non-audio signal or an audio signal having a predetermined period. The transmission device according to claim 6, wherein
The audio clock reproduction unit outputs a frequency pclk of the received video clock and the frequency f of the first audio clock output as the audio clock information from the receiver.
pclk / P = f / Q
The transmission device is characterized in that the second audio clock is reproduced from at least one of the frequency division parameters P and Q satisfying the relationship and the transmission video clock having the same frequency as the reception video clock. . A receiving device in a digital interface for video / audio transmission,
Video / audio / packet separation that receives transmission data output from a transmission device and separates received video data, received video clock, received audio data, and sampling frequency information of the received audio data from the transmitted data And
A plurality of audio clocks having different frequencies are generated based on a reference clock given from the outside, and one audio clock is used as a reception audio clock from the plurality of audio clocks according to the sampling frequency information. A reception audio clock generator for selecting and outputting;
A reception audio processing unit that outputs the reception audio data in synchronization with the reception audio clock output by the reception audio clock generation unit;
Audio clock information including at least information on the frequency of the first audio clock is generated from a first audio clock that is one of a plurality of audio clocks generated by the reception audio clock generation unit, and is transmitted to the transmission device. A receiving apparatus comprising: an audio clock information generating unit for outputting. The receiving device according to claim 10, wherein
The audio clock information generation unit generates audio information obtained by modulating a predetermined audio signal in units of frames in which a synchronization pattern is embedded in synchronization with the first audio clock, and as the audio clock information A receiving apparatus that outputs the data. The receiving device according to claim 11, wherein
The receiving apparatus according to claim 1, wherein the predetermined audio signal is a non-audio signal or an audio signal having a predetermined period. The receiving device according to claim 10, wherein
The audio clock information generator generates a frequency f between the first audio clock and a frequency pclk of the received video clock.
pclk / P = f / Q
The receiving apparatus is characterized in that frequency division parameters P and Q satisfying the relationship are generated and at least one of the frequency division parameters P and Q is output as the audio clock information. The receiving device according to claim 13.
One of the frequency division parameters P and Q is set to a predetermined fixed value, and the other is output by the audio clock information generation unit as the audio clock information.

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