JP2619041B2 - Audio signal transmission method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a main transmission path receiving apparatus for transmitting an audio signal having a larger amount of information (signal band) than can be transmitted by the main transmission path. The present invention relates to an audio signal transmission system for transmitting data via a main transmission path and a sub transmission path with compatibility, and a transmission and reception apparatus for the same.

(Summary of the Invention) The present invention relates to a system for transmitting an audio signal through two transmission lines, and transmits a baseband of an audio signal provided on a main transmission line while limiting a band thereof, and transmitting the main signal on a sub-transmission line. The high-frequency component removed by the band limitation is transmitted on the transmission line, and the reception side demodulates and adds the signals transmitted on both transmission lines with compatibility with the receiving device for the main transmission line. .

Thus, the audio signal having a higher frequency component can be restored as compared with the case where only the main transmission path is used, and the service of the audio signal can be received only by the main transmission path receiving apparatus that does not have the receiving equipment of the sub transmission path. it can.

(Prior Art) Conventionally, there has been a technique in which an audio signal is divided and transmitted through a plurality of transmission paths, and the received audio signal is added to the receiving side to reproduce the original audio signal. As described above, there has been no method of performing split transmission with compatibility with a main transmission path receiving device capable of obtaining sufficient sound quality by itself.

(Problems to be Solved by the Invention) The conventional divided transmission method is intended to transmit a high-quality sound signal with a large amount of information by combining several transmission lines with a small transmission capacity. Is simple, information cannot be correctly transmitted if a transmission failure occurs in any one of a plurality of transmission paths used.

Therefore, the present invention solves the above-described problems, and can transmit information with almost sufficient sound quality only by using the main transmission path.
In addition, the audio that can reproduce the original audio signal having a wider band frequency characteristic than the main transmission path alone can receive on the receiving side by additionally transmitting high-quality information that cannot be transmitted by the main transmission path via the sub transmission path. It is intended to provide a signal transmission system and a transmission / reception device therefor.

(Means for Solving the Problems) In order to achieve this object, the audio signal transmission system of the present invention converts an original audio signal having a larger amount of information than can be transmitted by the transmission capacity of the main transmission line into the main transmission signal. Via the transmission path and the sub-transmission path, and on the receiving side, from the signal transmitted on both transmission paths with compatibility with the receiving device for the main transmission path, the more information amount In restoring the audio signal having the signal, on the transmission side, the original audio signal includes a low-pass filter and a first sampling frequency conversion device having a first sampling frequency defined by the upper limit frequency of the filter. To the main transmission path, and on the other hand, a high-frequency component of the original audio signal having a frequency equal to or higher than the upper limit frequency of the low-pass filter having a second sampling frequency defined by the bandwidth of the high-frequency component. To sub-transmission line via sampling frequency converter At the receiving side, the receiving side converts the signals transmitted through the main transmission path and the sub transmission path into a third sampling frequency conversion having a third sampling frequency defined by the upper limit frequency of the original audio signal. After passing through the device, the two are added to restore the audio signal, so that an audio signal having a wider band than in the case of using only the main transmission path is obtained.

An audio signal transmitting apparatus according to the present invention is a transmitting apparatus used for the transmission system, and the apparatus obtains the low-pass filter, the first sampling frequency conversion apparatus, and a high-frequency component of an original audio signal. And a second sampling frequency conversion device.

Also, the audio signal receiving apparatus of the present invention is a receiving apparatus used for the transmission system, and the apparatus comprises two third signals.
It is characterized by comprising a sampling frequency converter and an adder for adding output signals from the two converters.

(Operation) According to the transmission system of the present invention, the main transmission is performed by limiting the band of the original audio signal having a larger amount of information that cannot be transmitted with the transmission capacity of the main transmission path, specifically, the higher-frequency signal component. Transmission via the channel and the remaining high-frequency components via the sub-transmission line are compatible with the receiver for the main transmission line, so that even if a transmission failure occurs in the sub-transmission line, sound quality is maintained to some extent. The reproduced audio signal can be reproduced.

(Example) Hereinafter, the present invention will be described by way of examples with reference to the accompanying drawings.

FIG. 1 and FIG. 2 show schematic diagrams of a transmitting encoder and a receiving decoder according to the transmission system of the present invention.

In the encoder shown in FIG. 1, the input original audio signal may be an analog signal, but a digital signal is preferred for later signal processing, and its sampling frequency is the upper limit frequency of the baseband of the audio signal to be transmitted. (Nyquist frequency) or more. The input signal a is divided by the low-pass filter 1 and the subtractor 4 into a signal b whose frequency band is limited up to the transmission band of the main transmission line and a signal d having a higher frequency component than that. At this time, a signal delay circuit for adjusting the timing of the signal a to the subtractor 4 with the signal b is necessary for the circuit reaching the subtracter 4, but is omitted here.

Next, the signal b is subjected to the first sampling frequency conversion by the first sampling frequency conversion device 2. At this time, it is assumed that the first sampling frequency is a frequency equal to or higher than the Nyquist frequency defined by the upper limit frequency of the low-pass filter. The output signal c of the conversion device 2 is further transmitted to the main transmission line via the signal delay circuit 3. The signal delay circuit 3 is generally used to adjust the timing of signal transmission to the main transmission path and the sub transmission path, but the amount of adjustment of the timing adjustment of the signal f and the signal h in the adder 10 on the decoder side shown in FIG. If this is also included, it is convenient because the configuration on the decoder side can be simplified, and here, the delay amount corresponding to that case is also included.

On the other hand, the signal d undergoes the second sampling frequency conversion by the second sampling frequency conversion device 5 to output the signal e. At this time, the second sampling frequency is desirably a frequency equal to or higher than the Nyquist frequency of the high-frequency band width of the input original audio signal. The signal e is further converted to a bit
, And is transmitted to the sub-transmission path. At this time, the device 6 is not an essential component of the present invention.

FIG. 2 is a schematic block diagram of the receiving side decoder. Here, the signal transmitted through the main transmission path undergoes the third sampling frequency conversion by the third sampling frequency converter 3 to output a signal f. . It is desirable that the third sampling frequency is a frequency equal to or higher than the Nyquist frequency of the upper limit frequency of the band in which the original audio signal is to be transmitted.

On the other hand, if the signal transmitted on the sub-transmission path is bit-compressed on the encoder side, it undergoes bit expansion by the bit expansion device 8 and is restored to the same bit range as the signal e. The same as the signal transmitted on the
The sampling frequency conversion is performed by the third sampling frequency converter 9. Thereafter, the output h is added to the timed signal f by the adder 10 to reproduce a high quality audio signal. On the other hand, the signal f is separately output and reproduced as an audio signal of the receiving device for the main transmission path.

The first, second, and third sampling frequencies may each be a frequency equal to or higher than a predetermined Nyquist frequency, but the sum of the first and second frequencies is the third frequency in terms of signal processing simplicity. It is desirable. Preferably, the third sampling frequency is equal to the sampling frequency of the input original audio digital signal. In this case, the following numerical relationships are established as an example.

Input original audio signal: 20 kHz band and 48 kHz sampling frequency Low pass filter: upper limit 15 kHz 1st sampling frequency: 32 kHz sampling frequency 2nd sampling frequency: 16 kHz sampling frequency 3rd sampling frequency: 48 kHz sampling frequency Bit The compression and decompression are described in detail in Japanese Patent Application Laid-Open No. 63-16718, "quasi-instantaneous compression difference encoding method", and the description thereof is omitted here.

(Effects of the Invention) As described in detail above, in the audio signal transmission system of the present invention, a high-quality audio signal of a wide band is band-limited on a main transmission path, and only a certain amount of band is limited and transmitted. Almost satisfactory sound quality can be ensured even with information on the transmission line alone, and signal components that could not be transmitted due to band limitation on the sub transmission line are transmitted and added to the signal transmitted on the main transmission line on the receiving side, so wideband Can be restored. Even if a transmission failure occurs in the sub-transmission line, a certain level of sound quality can be secured on the receiving side. Further, compatibility with the receiving device for the main transmission path can be ensured.

[Brief description of the drawings]

FIG. 1 and FIG. 2 show schematic diagrams of a transmission side encoder and a reception side decoder according to an embodiment of the present invention, respectively. DESCRIPTION OF SYMBOLS 1 ... Low-pass filter 2,5,7,9 ... 1st, 2nd, 3rd, 3rd sampling frequency converter 3 ... Signal delay circuit 4,10 ... Subtracter and adder 6 , 8 …… Bit compression and decompression device

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Taiji Nishizawa 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Research Institute of Broadcasting Technology (56) References JP-A-63-110830 (JP, A) Kaisho 62-51322 (JP, A)

Claims (5)

(57) [Claims] An original audio signal having a larger amount of information than can be transmitted by the transmission capacity of the main transmission path is transmitted through the main transmission path and the sub transmission path, and the reception side transmits the original audio signal. In restoring the audio signal having the larger amount of information from the signals transmitted on both transmission paths in a manner compatible with the main transmission path receiving apparatus, the transmitting side converts the original audio signal into The signal is sent to the main transmission path via a low-pass filter and a first sampling frequency conversion device having a first sampling frequency defined by an upper limit frequency of the filter, and on the other hand, an upper limit of the low-pass filter. The high-frequency component of the original audio signal having a frequency equal to or higher than the frequency is transmitted to the sub-transmission path via the second sampling frequency converter having the second sampling frequency defined by the bandwidth of the high-frequency component, and transmitted to the receiving side. If it is, transmission on the main transmission line and sub transmission line Each of the received signals is passed through a third sampling frequency converter having a third sampling frequency defined by the upper limit frequency of the original audio signal, and then the two are added to restore the audio signal. An audio signal transmission method characterized by obtaining an audio signal having a wider band than in the case of (1). 2. The transmission method according to claim 1, wherein a sum of the first sampling frequency and the second sampling frequency is equal to the third sampling frequency. . 3. The transmission system according to claim 1, wherein the original audio signal is a digital audio signal, wherein the sampling frequency of the digital audio signal is equal to the third sampling frequency. method. 4. A transmission device used in the transmission system according to claim 1, wherein the transmission device includes the low-pass filter, the first sampling frequency conversion device, and an original audio signal. An audio signal transmitting device, comprising: a subtractor for obtaining a high frequency component; and the second sampling frequency converting device. 5. A receiving apparatus used in the transmission system according to claim 1, wherein said receiving apparatus comprises two third sampling frequency converters and outputs from said two converters. An audio signal receiving device, comprising: an adder for adding a signal.