JP4718499B2 - Audio transmission apparatus and audio transmission method - Google Patents

Description

  The present invention relates to an audio transmission apparatus that transmits digital audio data using a plurality of transmission paths, and selects and outputs one normal digital audio data without interruption on the receiving side.

  In a digital video transmission system that transmits digital video data such as HD (High Definition) video data and SD (Standard Definition) video data on which digital audio data is superimposed, multiple digital video data are transmitted to improve transmission reliability. In some cases, a redundant configuration is used for transmission via a transmission line.

  FIG. 1 shows an example of a digital video transmission system adopting a redundant configuration in which digital video data is transmitted through two transmission paths. The digital video transmission system shown in FIG. 1 includes a video transmission device 1 and a video reception device 3. The video transmission device 1 includes a data branching unit 11 and data transmission units 12 and 13, and the video reception device 3 includes data reception units 31 and 32 and a data selection unit 33.

  The digital video data input to the video transmission device 1 is branched into the same two digital video data in the data branching unit 11, one of which is transmitted to the transmission path 5 by the data transmission unit 12 and the other is transmitted to the transmission path by the data transmission unit 13. 7 is sent out.

  The digital video data sent to the transmission line 5 is received by the data receiver 31 of the video receiver 3 and sent to the data selector 33. The digital video data sent to the transmission line 7 is received by the data receiving unit 32 of the video receiving device 3 and sent to the data selecting unit 33. The data selection unit 33 selects and outputs one digital video data out of the digital video data received from the data reception unit 31 and the digital video data received from the data reception unit 32.

  For example, when digital video data transmitted through the transmission line 5 out of two transmission lines is selected and output by the video reception device 5, the one selected due to a failure in the transmission line 5 or a device failure When an error occurs in the digital video data, the data selection unit 33 performs switching so that the digital video data transmitted through the transmission path 7 is output.

  Although the above example is an example of a digital video data transmission system, the same redundant configuration as that shown in FIG. 1 can be used in a transmission system that transmits only digital audio data. In the present specification and claims, “digital audio data” includes digital audio data transmitted by being superimposed on digital video data.

As an example of the prior art document, there is Patent Document 1 in which a technique of switching and using necessary audio data from a plurality of digital audio data is disclosed.
Japanese Unexamined Patent Publication No. 08-237216

  In a redundant transmission system using a plurality of transmission paths as shown in FIG. 1, if there is a delay difference between the plurality of transmission paths, switching from the active system to another system on the receiving side causes images and audio. There is a problem in that a shift occurs and instantaneous interruption occurs without maintaining continuity.

  Regarding this problem, for image data in digital video data, for example, a method has been proposed in which the contents of an image itself are recognized and the identity between a plurality of images is determined to synchronize between a plurality of systems. However, no appropriate technique for synchronizing audio data has been proposed. Even if a plurality of audio data are synchronized, there are the following problems.

  In digital video data on which audio data such as HD video data is superimposed, the number of audio packets that can be superimposed on the audio data superimposition region of the video frame is defined in the standard. For example, when audio data of 48 kH sampling is superimposed on 1080 / 59.94i video, the number of audio packets of one channel pair to be superimposed per 5 image frames is defined as 8008 according to the SMPTE299M standard. Accordingly, when there are not enough audio packets to be superimposed on the video frame, for example, when the image is frozen due to a device failure or the like, fixed value data such as mute audio is generated and superimposed.

The audio data superimposed on the digital video data is given an error detection code such as a checksum, but before being superimposed on the video data, the fixed data such as the mute audio is generated and the error correction code is calculated. When superimposing the added voice packet, the mute voice or the like cannot be detected as an error in the error correction code check on the receiving side. Therefore, the normal voice data of another system can be obtained only by checking the error correction code. Cannot be distinguished, and normal audio data cannot be selected. In addition to the above case, it is possible that an abnormality of the voice data that cannot be detected by the error detection code may occur, and in that case, the abnormality cannot be detected and normal voice data cannot be selected.
In addition, even in a transmission system that transmits only digital audio data, there may be cases where audio data of fixed value data such as mute audio is generated due to equipment failure or the like and cannot be detected by an error detection code. Therefore, there arises a problem similar to the above that normal voice data cannot be identified and selected.

  The present invention has been made in view of the above points, and allows digital audio data to be transmitted through a plurality of transmission lines and synchronized on the receiving side, and normal digital audio data to be transmitted without interruption. The purpose is to provide technology for selection.

The above-described problem is an audio transmission apparatus used in a redundant digital audio transmission system that transmits digital audio data through a plurality of transmission paths, and obtains a voice packet of each system transmitted through the plurality of transmission paths. A packet acquisition means and a predetermined number of voice packets based on a bit value existing in a specific cycle in a voice packet are grouped into one group, and an arithmetic value of voice packet data in the group is calculated for each system. means and, using each reception timing group to which the arithmetic values match between a plurality of systems to synchronize voice packets between multiple systems, and synchronization means for outputting, of the synchronized output from the synchronization means Selecting means for selecting and outputting one system voice packet from a plurality of system voice packets taken, the voice transmission apparatus comprising: A plurality of voice abnormality detection means for each system, each voice abnormality detection means comprising means for determining whether or not the received voice packet has a specific data pattern, Based on the determination result from the anomaly detection means, the specific data pattern is detected from voice packets in a predetermined number of systems or less, and the specific data pattern is detected from corresponding voice packets in other systems. If not, it is determined that there is an abnormality in the number of voice packets of the predetermined number or less, and the selection means does not select the number of voice packets of the predetermined number or less. This can be solved by an audio transmission device.

  When an abnormality is detected in the voice packet in the selected system, the selection unit may select and output a voice packet corresponding to another system instead of the voice packet, or the voice packet may be output. It is good also as selecting and outputting the voice packet of the corresponding group of another system instead of the group to include.

  According to the present invention, since digital audio data can be transmitted through a plurality of transmission lines and synchronized on the receiving side, a technique for selecting normal digital audio data without interruption can be realized.

  Embodiments of the present invention will be described below with reference to the drawings.

(About the principle of the synchronization method)
Digital audio data to be superimposed on digital video data or digital audio data for transmitting only audio is packetized, and a channel status is added in addition to an error detection code and invalid data bits.

  This channel status is added to one voice packet bit by bit, and is identified as one channel status by extracting the bit from a plurality of continuous voice packets.

  For example, in the case of the ANSI S4.40 (AES-3) standard, which is a digital audio data transmission standard, one channel status of 24 bytes is obtained in units of 192 samples (packets) of one stereo channel. Further, a synchronization bit called a Z flag is defined as a synchronization signal indicating the start point of the channel status. In this embodiment, digital audio data transmitted through a plurality of paths is synchronized using this synchronization bit. Hereinafter, the ANSI S4.40 (AES-3) standard will be described, but the present invention can be applied to any system as long as the digital audio transmission system adopts the same synchronization bit as described above.

FIG. 2 shows a conceptual diagram of processing for establishing synchronization in the receiving-side audio transmission apparatus. FIG. 2 shows a 0-system received voice packet, a 1-system received voice packet,..., An n-system received voice packet received from the 0-n transmission lines.
In the processing shown in FIG. 2, in the received voice packets of each system, 192 packets in the range constituting one channel status are defined as one frame based on the synchronization bit in 192 packets, and the sum of the voice data in the voice packets in the frame Calculate The sum of the audio data of each frame in the other system received within a predetermined time before and after the start timing of the frame of the 0-system received voice packet (the start timing of the voice packet including the synchronization bit) , 0 sum of received voice packets is compared with the above sum. Then, the frames having the same sum are regarded as the same frames in the other systems, and the voice packets of each system are synchronized and output using the difference in the start timing (reception timing) of the same frame between the systems. Here, the voice packets of each system are output in synchronization with the system with the longest delay.

  In FIG. 2, 0-series Σ (Audio data) m is a frame from the audio packet including the synchronization bit to the audio packet immediately before the audio packet including the next synchronization bit in the 0-system received audio packet. The sum of audio data in the frame is shown. 0 system Σ (Audio data) m + 1 indicates the sum of audio data of the next frame of 0 system Σ (Audio data) m, and n system Σ (Audio data) m is a synchronization bit in the n system received audio packet. The sum of the audio data in the m-th frame is shown from the audio packet including the frame to the audio packet immediately before the audio packet including the next synchronization bit.

  For example, when the transmission path is two systems of the 0 system and the 1 system, the head timing of the m-th frame of the 0-system received voice packet is T, and the same frame as the 0-system m-th frame in the 1-system received voice packet If the start timing of the frame determined to be T + t, the 0-system received packet is delayed by the time t by buffering it for the time t and output. Thereby, the same voice packet can be simultaneously output in the 0-system and the 1-system, and synchronization can be established.

  Such processing is performed for each frame of voice packets sent continuously. Further, it may be performed every predetermined time instead of every frame.

  In the above example, the sum of the voice data in each frame of each received voice packet is calculated and used for comparison. However, an arithmetic value that is not the sum can be calculated and used for comparison. For example, an average value obtained by dividing the sum of the audio data for each audio packet by the number of audio packets can be used.

  In the above example, the arithmetic value for 192 voice packets from the voice packet including the synchronization bit to the voice packet immediately before the voice packet including the next synchronization bit is obtained. Arithmetic values in groups up to a smaller predetermined number of voice packets may be calculated and used for comparison.

  In the above example, the 0 system is used as a reference, but any system may be used as a reference. By using the synchronization method as described above, it is possible to switch voice packets between multiple systems without interruption.

(Device configuration)
By combining the synchronization method and the voice abnormality detection mechanism, it is possible to output only normal received voice packets without interruption. FIG. 3 shows a functional configuration example of a voice uninterruptible switching device 20 (also referred to as a voice transmission device) that combines such a synchronization method and a voice abnormality detection mechanism.

  As shown in FIG. 3, the voice uninterruptible switching device 20 detects voice packet anomalies in each system and outputs voice anomaly detectors 21-0 to 21-n that output data necessary for synchronization. And a voice synchronization selection unit 22 for selecting and outputting a voice packet of one system in synchronization between the systems.

  When the audio uninterruptible switching device 20 is applied to a digital video transmission system in which audio is superimposed and transmitted, as shown in FIG. A separation unit 25 that separates image data is provided, and a multiplexing unit 24 that multiplexes audio data and image data and outputs digital video data after the audio uninterruptible switching device 20 is provided. Further, an image uninterruptible switching device 26 is provided. The multiplexing unit 24 is provided as necessary.

  In the configuration shown in FIG. 4, the separation unit 25 separates each digital video data received from a plurality of systems into audio data and image data, and supplies them to the audio uninterruptible switching device 20 and the image uninterruptible switching device 26. The voice uninterruptible switching device 20 and the image uninterruptible switching device 26 select normal audio and images, respectively, and supply them to the multiplexing unit 24. The multiplexing unit 24 multiplexes the supplied audio data and image data and outputs them as digital video data. It should be noted that when the audio and the image are separated / multiplexed, the audio and the video are synchronized.

  FIG. 5 shows an example of the functional configuration of the voice abnormality detection unit 21. As shown in FIG. 5, the audio abnormality detection unit 21 includes a specific data pattern detection unit 211 that performs error notification when a specific data pattern (all 0s or all 1s) such as mute data is detected, an error detection code, and the like. An error detection unit 212 that detects an error in a voice packet by using the existing error check method, calculates an arithmetic value such as a sum corresponding to the synchronization method described in FIG. 1, and outputs the arithmetic value and the start timing of the frame And a synchronization data generation / output unit 213.

  FIG. 6 shows a functional configuration example of the voice synchronization selection unit 22. As shown in FIG. 6, the audio synchronization selection unit 22 includes a buffer unit 221-0 to 221-n, a reading unit 222, a selection unit 223, a matching audio determination unit 224, and an audio abnormality determination unit 225 for each system. is doing.

  The buffer unit 221 temporarily stores the received voice packets of each system, and the reading unit 222 reads out the voice packets of each system in synchronization based on the signal from the coincidence voice determining unit 324. Further, the selection unit 223 selects and outputs one system video from a plurality of audio packets without instantaneous interruption based on the signal from the audio abnormality determination unit 225.

  The coincidence sound determination unit 224 performs coincidence determination of the sound data as shown in FIG. 1, and outputs the start timing of the coincident sound frame in each system. Then, the reading unit 222 synchronizes by adjusting the read timing from the buffer according to the difference in the head timing in each system.

  Further, the audio abnormality determination unit 225 receives the abnormality determination result from each audio abnormality detection unit 21, determines an abnormal system, and outputs the system to the selection unit 223.

  For errors detected by normal error check processing, the system in which the error has occurred may be output as it is. However, as for the result of abnormality determination using a specific data pattern, specific data depends on the characteristics of the sound when viewed for each system. Even if a pattern is detected, it may not be abnormal. Therefore, when a determination result is obtained that a specific data pattern has been detected in a certain system, and the specific data pattern is not detected in the corresponding voice packet in all other systems, Judged to be abnormal. That is, when a specific data pattern is obtained in a plurality of systems, it is determined that it is due to the characteristics of the sound, and it is not determined that the sound is abnormal. For example, in the case of two systems, when a specific data pattern is detected in one system and not detected in another system, it is determined that the voice packet of the system is abnormal, and in both systems When a specific data pattern is detected, it is not determined that the specific data pattern is abnormal.

  Further, in the case of more than two systems, the predetermined data pattern is detected in a system of a predetermined number or less, and the specific data pattern is not detected in the corresponding voice packet in the other system, the predetermined data pattern is detected. It may be determined that the number of voices of the number less than that number is abnormal. For example, in the case where there are four systems, when a specific data pattern is detected only in two or less systems, it is determined that there is an abnormality in the voice packet of the system.

  Note that the error notification shown in FIG. 5 includes the start timing of the voice packet in which the error is detected, and the voice abnormality determination unit 225 shown in FIG. 6 indicates the start timing of the matching voice frame from the matching voice determination unit 224. By using the information, the corresponding voice packet can be identified. Further, by using the information on the start timing of the matching frame from the matching voice determination unit 224, a signal indicating the abnormality determination result is transmitted to the selection unit 223 in synchronization with the reading unit 222. Further, error detection and specific data pattern detection may be performed on the synchronized voice packet output from the reading unit 222.

  The selection unit 223 that has received the information of the system in which the voice packet is abnormal from the voice abnormality determination unit 225 selects and outputs the voice packet of the system excluding the system determined to be abnormal. When there are a plurality of systems other than the system determined to be abnormal, for example, voice packets of a predetermined system, a system designated from the outside, or an arbitrarily selected system are output. According to the method of the present embodiment, since synchronization between systems is taken, if an abnormality is detected in a system while a system is selected, there is no instantaneous interruption to another system. It is possible to switch with.

  An example in which a specific data pattern is detected and system switching is performed will be described with reference to FIGS. The example shown in FIGS. 7 and 8 is an example in the case of two systems, and shows a state in which synchronization between the 0-system received voice packet and the 1-system received voice packet is achieved by the method described above.

  In the example illustrated in FIG. 7, switching is performed for each voice packet, and when the selection unit 223 selects the 0 system as the active system, a specific data pattern is detected in the third voice packet of the 0 system, Since the specific data pattern was not detected in the third voice packet of the 1 system, only the third voice packet of the 0 system is switched to the 1 system voice packet and output.

  In the example shown in FIG. 8, switching is performed in units of frames consisting of 192 voice packets, and when the selection unit 223 selects the 0 system as the active system, a specific data pattern is used for the third voice packet of the 0 system. Is detected, and the specific data pattern is not detected in the third voice packet of the 1 system. Therefore, the 0 system frame including the audio packet in which the specific data pattern is detected is switched to the 1 system frame and output. .

  The voice uninterruptible switching device 20 shown in FIG. 3 may be provided inside a receiving device that receives digital audio data of a plurality of systems from a transmission network, or may be provided outside. Further, in the case where only the purpose is to achieve synchronization, a configuration relating to the audio abnormality determination and the device configuration excluding the selection unit 223 from the configuration of the audio uninterruptible switching device 20 in FIG. In this case, the apparatus includes a voice packet acquisition unit that acquires voice packets of each system transmitted through a plurality of transmission paths, and a predetermined number of voices based on a bit value existing in a specific cycle in the voice packet. A packet is defined as one group, and a calculation means for calculating an arithmetic value of voice packet data in the group for each system, and each reception timing of a group in which the arithmetic value matches between a plurality of systems is used. It becomes an apparatus provided with the synchronization means which synchronizes a voice packet between them and outputs it.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

It is a figure which shows the example of the digital video transmission system which employ | adopted the redundant structure. It is a figure for demonstrating the process for synchronization establishment. It is a figure which shows the example of a function structure of the audio | voice uninterruptible switching device. It is a figure which shows the structural example in the case of applying the audio | voice uninterruptible switching apparatus 20 to digital video transmission. FIG. 3 is a diagram illustrating an example of a functional configuration of a voice abnormality detection unit 21. 3 is a diagram illustrating an example of a functional configuration of a voice synchronization selection unit 22. FIG. It is a figure which shows Example 1 in the case of switching a system by detecting a specific data pattern. It is a figure which shows Example 2 in the case of switching a system by detecting a specific data pattern.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video transmission apparatus 3 Video reception apparatuses 5 and 7 Transmission path 11 Data branch part 12, 13 Data transmission part 31, 32 Data reception part 33 Data selection part 21 Audio | voice abnormality detection part 22 Audio | voice synchronization selection part 24 Multiplexing part 25 Separation part 26 Image uninterruptible switching device 211 Specific data pattern detection unit 212 Error detection unit 213 Synchronization data generation output unit 221 Buffer unit 222 Reading unit 223 Selection unit 224 Matching voice determination unit 225

Claims (4)

An audio transmission device used in a redundant digital audio transmission system for transmitting digital audio data through a plurality of transmission paths,
Voice packet acquisition means for acquiring voice packets of each system transmitted through the plurality of transmission paths;
A calculation means for setting a predetermined number of voice packets based on bit values existing in a specific period in the voice packet as one group, and calculating an arithmetic value of voice packet data in the group for each system;
Synchronizing means for synchronizing and outputting voice packets between a plurality of systems using each reception timing of a group in which the arithmetic value matches between the systems,
Selecting means for selecting one voice packet from a plurality of synchronized voice packets output from the synchronizing means, and outputting the selected voice packet;
The voice transmission device includes a plurality of voice abnormality detection means for each system, each voice abnormality detection means includes means for determining whether or not a received voice packet has a specific data pattern,
The voice transmission device detects the specific data pattern from voice packets in a system of a predetermined number or less based on determination results from the plurality of voice abnormality detection means, and the corresponding voice packets of other systems When the specific data pattern is not detected, it is determined that there is an abnormality in the number of voice packets of the predetermined number or less, and the number of voice packets of the number or less of the predetermined number is determined. An audio transmission apparatus , wherein the selection means does not select . It said selection means, when an abnormality is detected in the audio packet in the system being selected, in claim 1, characterized in that selects and outputs a corresponding speech packets of other systems in place of the voice packet The audio transmission device according to the description. The selection means, when an abnormality is detected in a voice packet in a selected system, selects and outputs a voice packet of a corresponding group in another system instead of the group including the voice packet. The voice transmission device according to claim 1 . An audio transmission method executed by an audio transmission device used in a redundant digital audio transmission system for transmitting digital audio data through a plurality of transmission paths,
A voice packet acquisition step of acquiring voice packets of each system transmitted through the plurality of transmission paths;
A calculation step of setting a predetermined number of voice packets based on bit values existing in a specific cycle in the voice packet as one group, and calculating an arithmetic value of voice packet data in the group for each system;
A synchronization step of synchronizing and outputting voice packets between a plurality of systems using each reception timing of a group in which the arithmetic value is matched between the systems;
A selection step of selecting and outputting one system voice packet from a plurality of synchronized system voice packets output by the synchronization step, and a voice transmission method comprising:
The voice transmission device includes a plurality of voice abnormality detection means for each system, each voice abnormality detection means includes means for determining whether or not a received voice packet has a specific data pattern,
The voice transmission device detects the specific data pattern from voice packets in a system of a predetermined number or less based on determination results from the plurality of voice abnormality detection means, and the corresponding voice packets of other systems When the specific data pattern is not detected, it is determined that there is an abnormality in the number of voice packets of the predetermined number or less, and the number of voice packets of the number or less of the predetermined number is determined. A voice transmission method , wherein no selection is made in the selection step .

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