JP4075155B2 - Data transmission method for digital audio data - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data transmission method when digital audio data is transmitted between digital audio data processing units, for example, when digital audio data is transmitted between two DSPs (Digital Signal Processors).
[0002]
[Prior art]
In general, a stereo digital audio processing device has an interface that alternately inputs and outputs R channel and L channel data at a fixed timing.
[0003]
In the type 1 device as shown in FIG. 4A, the sample timing of the L channel data is defined at the rising edge of the word clock and the R channel data is defined at the falling edge.
[0004]
However, a device such as type 1 in FIG. 4A may not be connected to a device having the same input / output interface, but may be connected to a device such as type 2 shown in FIG. Alternatively, left and right data may not always be output alternately. The latter occurs because a certain type of device may process a plurality of data collectively when performing compression processing. If this happens, the LR channel data cannot be input / output correctly. Therefore, in order to compensate for the correct input / output interface, an external logic circuit and RAM are separately provided.
[0005]
[Problems to be solved by the invention]
However, the provision of an external logic circuit or RAM has a problem of increasing the number of parts and increasing the cost.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a digital audio data transmission method that solves the above problems by adding attribute information such as a channel to digital audio data.
[0007]
[Means for Solving the Problems]
According to the data transmission method of digital audio data according to the present invention, when digital audio data is transmitted between digital audio data processing units, when transmitting a base clock, a word synchronization clock, and data in parallel from the transmission side , Data indicating validity and data indicating an audio channel or data indicating invalidity is added as attribute data and then transmitted, and data processing is performed on the receiving side based on the attribute data.
[0008]
The attribute data can be data representing an audio channel, or data representing invalidity or validity.
[0009]
As described above, by adding attribute data to data to be transmitted, the attribute of the data as digital audio data, that is, whether it is an L channel or an R channel, even without an interface as shown in FIG. Thus, data transmission can be performed in the interface format as shown in FIG. Further, by adding data indicating invalidity / validity of data to the attribute data, the data can be correctly restored on the receiving side even if the data is transmitted discretely.
[0010]
Further, if the attribute data is added outside the data occupation period between the synchronous clocks as in claim 2, the length of the entire data is not increased by the attribute data.
Further, as in claim 3 , when data transmitted once by the transmission side is transmitted again, data indicating invalidity is added to the received data as attribute data and transmitted to the reception side, and the transmission side becomes a pair. If one of the data cannot be transmitted, data indicating invalidity may be added as attribute data to the other of the paired data and then transmitted to the receiving side .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram of a data transmission apparatus for digital audio data according to an embodiment of the present invention.
[0012]
The digital audio data processing unit A and the digital audio data processing unit B are each composed of a DSP, and communication of digital audio data between A and B is performed by a communication line C. The communication line C includes a line for transmitting a base clock, a line for transmitting a word synchronization signal (sync), and a line for transmitting data. The base clock is a data sample clock and is common between the two data processing units A and B. The word synchronization clock is a clock indicating the data sampling start timing, and is the same as the sync clock shown in FIG. That is, in this example, the general-purpose transmission format shown in FIG. 4B is used.
[0013]
In this example, 1 word is set to 128 clocks, and L channel data and R channel data are transmitted in 32 bits each in 1 word. Therefore, the word synchronization clock is at the first clock and the 65th clock. Since the data is composed of 32 bits for each of the L and R channels, there is a data unoccupied period, that is, a 32-bit non-data period within a period corresponding to one word synchronization clock. Therefore, in this embodiment, attribute data (status) indicating the attribute of the immediately preceding data is added to the 32-bit non-data period for transmission. As a result, for example, in the digital audio data processing unit A, when the L channel is added to the status of the data A and the R channel is added to the status of the data B, the digital audio data processing unit B sees the respective statuses. The data A and B can be easily distributed as L channel data and R channel data. The status can be not only data for distinguishing the L channel and the R channel, but also data indicating invalidity. The reason why it is necessary to add invalid data as a status is as follows.
[0014]
(1) When a DSP is used for the digital audio data processing unit A, the process of storing data in the ring buffer and the process of transmitting data are asynchronous, so that the data transmitted once is transmitted again. Sometimes. In this case, the status is invalidated for data to be transmitted again.
[0015]
(2) For the same reason, when data for the L channel cannot be transmitted, it is necessary to invalidate the data for the R channel paired therewith. In this case, the data status for the R channel is invalidated.
[0016]
As described above, the data indicating the L channel and the R channel or invalidity is used as the status, so that the audio data can be correctly transmitted while synchronizing between the two digital audio data processing units A and B.
[0017]
2 (1) to 2 (2) show the types of status data. (1) is a typical example, and the statuses of the data A and B in 1 word are L channel and R channel, respectively. (2) shows a case where both data A and B are invalid. In either case, the validity of the data A and B can be determined on the receiving side, and if valid, the data can be correctly distributed to the L channel and the R channel.
[0018]
FIG. 3 shows a case where the digital audio data is compressed (encoded) in the DSP 1 into TwinVQ (music compression technology developed by NTT) and transmitted to the DSP 2 for expansion (decoding) via the data bus. A connection example is shown. The DSP 2 decodes the TwinVQ data and outputs it as an audio signal (music signal) via the DAC (D / A converter) 3.
[0019]
In the above configuration, the TwinVQ data transmitted from the DSP 1 to the DSP 2 conforms to the general-purpose transmission format shown in FIG. That is, 1 word is 128 bits, and 32-bit data A and B (generally, L channel data and R channel data, respectively) are transmitted together with the status in this 1 word. The status is data indicating whether the data A and B are L channel, R channel, or invalid, respectively.
[0020]
The status may include other data representing the attributes of the digital audio data.
[0021]
【The invention's effect】
According to the present invention, even in a data processing unit conforming to a general-purpose data transmission format as shown in FIG. 4B, attribute data peculiar to transmission data, for example, L channel and R channel data is added. As a result, even if there is no special interface circuit such as an external circuit, data can be accurately processed between the data processing units.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram of a digital audio data processing system according to an embodiment of the present invention. FIG. 2 is a diagram showing status types. FIG. 3 is a diagram showing an example of using a DSP in a digital audio data processing unit. FIG. 4 is a diagram showing a processing format of a digital audio data processing unit.

Claims (3)

A transmission method for transmitting digital audio data between digital audio data processing units,
When transmitting the base clock, word synchronization clock, and data in parallel from the transmission side, the data indicating the validity of the data and the data indicating the audio channel or the data indicating the invalidity are added as attribute data and transmitted. A data transmission method of digital audio data, characterized in that data processing is performed on the receiving side based on attribute data. The attribute data is added outside the data occupation period between word synchronization clocks.
The data transmission method of digital audio data according to claim 1. Wherein when the transmission side transmits the data transmitted once again transmits the data representing the disabled the received data to the receiving side from added as the attribute data,
When the transmitting side could not transmit one of the paired data, the data representing invalidity is added to the other of the paired data as the attribute data, and then transmitted to the receiving side.
The data transmission method of digital audio data according to claim 1 or 2.

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