JP2015011076A - Acoustic signal encoder, acoustic signal encoding method, and acoustic signal decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select single-channel encoding or channel-pair encoding on the basis of a correlation between channels included in an acoustic signal of a multi-channel acoustic system.SOLUTION: The present invention is an acoustic signal encoder 1 for encoding an acoustic signal of multi-channel acoustic system, the acoustic signal encoder comprising: a channel separation unit 10 for separating, on the basis of a correlation between channels included in the acoustic signal, each channel into channels to be encoded in a single channel and channels to be encoded in pairs of two channels; encoding units 20, 30 for encoding each channel in a single channel or in pairs of two channels in accordance with the result of separation; and a multiplexing unit 40 for multiplexing encoded data of each channel and channel-pair information indicating the channels encoded in pairs of two channels.

Description

  The present invention relates to an acoustic signal encoding device, an acoustic signal encoding method, and an acoustic signal decoding device compatible with a multi-channel acoustic system.

  In the future, when broadcasting Super Hi-Vision, the issue is how to encode 22.2 multi-channel sound, which is Super Hi-Vision sound. A typical method for compression encoding with high sound quality among the existing technologies is MPEG-4 AAC (Advanced Audio Coding). AAC is a scheme that combines single channel coding and two channel pair coding, but it is not always clear what channel pairs are preferred for 22.2 multichannel acoustic signals. (For example, refer nonpatent literature 1).

Marina Bosi, Richard E. Goldberg, "Introduction to Digital Audio Coding and Standards" Springer, 2002-12-31

  For example, the MPEG-2 AAC Annex defines a 22.2ch encoding scheme. This is a system in which a channel corresponding to the median plane is encoded as a single channel, and other channels are encoded as a channel pair at a symmetrical position. However, this only follows the conventional 5.1ch encoding method, and there is no guarantee that such a channel pair will lead to the maintenance of high encoding efficiency and sound quality.

  When encoding with MPEG-2 AAC or MPEG-4 AAC, single channel coding and channel pair coding (channel pair) are possible regardless of the number of channels of the three-dimensional audio signal. There is no method other than encoding with a combination of (element). The advantage of encoding with a channel pair is that efficient encoding can be performed using the correlation between the two channels, and the disadvantage is that crosstalk occurs between the two channels. The channel pair coding is preferably applied after forming a pair of channels having high correlation between signals, and when the correlation is low, it is desirable to code with a single channel.

  Therefore, an object of the present invention made in view of such a point is to be able to select single channel coding or channel pair coding based on the correlation between channels included in the acoustic signal of the multi-channel acoustic system. An object of the present invention is to provide an acoustic signal encoding device, an acoustic signal encoding method, and an acoustic signal decoding device capable of decoding the encoded acoustic signal.

  In order to solve the above-described problems, an acoustic signal encoding apparatus according to the present invention is an acoustic signal encoding apparatus that encodes an acoustic signal of a multi-channel acoustic scheme, and is provided between channels included in the acoustic signal. Based on the correlation, a channel allocating unit that distributes each channel into a channel that is encoded with a single channel and a channel that is encoded with two channel pairs, and according to the distribution result, each channel is encoded with a single channel. Or an encoding unit that encodes with two channel pairs, and a multiplexing unit that multiplexes the encoded data of each channel and channel pair information indicating a channel to be encoded with two channel pairs.

  Moreover, it is preferable that the said channel distribution part distributes each said channel at the time of every predetermined time or the timing which the said acoustic signal switches.

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included.

  For example, an acoustic signal encoding method according to the present invention is an acoustic signal encoding method by an acoustic signal encoding device that encodes an acoustic signal of a multi-channel acoustic method, and the processing procedure by the acoustic signal encoding device includes: Based on the correlation between the channels included in the acoustic signal, the step of distributing the channels into a channel that is encoded with a single channel and a channel that is encoded with a pair of two channels, and according to the distribution result, Encoding a channel with a single channel or encoding with a two-channel pair; and multiplexing encoded data of each channel with channel pair information indicating a channel to be encoded with a two-channel pair. Including.

  Furthermore, an acoustic signal decoding apparatus according to the present invention is an acoustic signal decoding apparatus that decodes an acoustic signal of a multi-channel acoustic scheme, and includes encoded data of each channel included in the acoustic signal from an input signal, A separation unit that separates channel pair information indicating a channel encoded by two channel pairs, and encoded data of a channel encoded by two channel pairs based on the channel pair information is encoded by two channel pairs , And the encoded data of the other channel includes a decoding unit that performs decoding corresponding to the encoding of a single channel.

  According to the acoustic signal encoding device and the acoustic signal encoding method according to the present invention, single channel encoding or channel pair encoding is selected based on the correlation between the channels included in the multichannel acoustic signal. Therefore, according to the acoustic signal decoding apparatus according to the present invention, the encoded acoustic signal can be decoded.

It is a figure which shows the functional block of the acoustic signal encoding apparatus which concerns on one Embodiment of this invention. It is a figure which shows the detailed functional block of a channel distribution part. It is a flowchart of the distribution process of a channel distribution part. It is a figure which shows the functional block of the acoustic signal decoding apparatus which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, the multi-channel sound signal in the present embodiment is a sound signal of 22.2 multi-channel sound, which is an audio system for Super Hi-Vision, for example, and the present invention is not limited to 5.1ch, 7.1ch, etc. The present invention can also be applied to multichannel acoustic signals.

  FIG. 1 is a functional block diagram of an acoustic signal encoding apparatus 1 according to an embodiment of the present invention. The acoustic signal encoding device 1 includes a channel allocating unit 10, a single channel encoding unit 20 and a channel pair encoding unit 30 that are encoding units, and a multiplexing unit 40.

  The channel sorting unit 10 sorts each channel of the input multi-channel acoustic signal into a channel to be subjected to single channel encoding and a channel to be subjected to channel pair encoding. Note that single channel encoding refers to encoding one channel independently, and channel pair encoding refers to encoding two channels as a pair. Channel allocator 10 outputs a channel to be subjected to single channel encoding to single channel encoder 20 and outputs a channel to be channel pair encoded to channel pair encoder 30. It should be noted that, as a result of channel allocation, all channels may be allocated to channels to be subjected to single channel encoding, or all channels may be allocated to channels to be channel pair encoded.

  FIG. 2 is a diagram illustrating detailed functional blocks of the channel allocation unit 10, and FIG. 3 is a flowchart of the allocation process of the channel allocation unit 10. The channel allocation unit 10 includes a signal storage unit 11, a channel pair selection unit 12, a channel information storage unit 13, and a signal distribution unit 14. The channel information storage unit 13 includes a channel name storage unit 131, One channel name storage unit 132 and a channel name pair storage unit 133 are provided. Hereinafter, the operation of each functional block of the channel distribution unit 10 will be described with reference to the flowchart of FIG.

  The signal storage unit 11 stores the multi-channel acoustic signal input to the channel distribution unit 10 for a predetermined time for each channel (step S1). The channel pair selection unit 12 stores a set of channel names (a list of channel names, hereinafter referred to as “channel name set” as appropriate) included in the multi-channel acoustic signal stored in the signal storage unit 11 in the channel name storage unit 131. (Step S2).

  The single channel name storage unit 132 stores the channel name of a channel for which single channel encoding is designated in advance by the producer or the like, and the channel pair selection unit 12 stores the channel name of the channel in question. It deletes from the channel name set of the part 131 (step S3). Here, the channels for which single channel coding is designated in advance include channels that should avoid crosstalk with other channels, such as 22.2ch Front Center Channel.

  The channel pair selection unit 12 calculates the correlation between the channels stored in the channel name storage unit 131 (step S4). For example, the channel pair selection unit 12 calculates the correlation between each channel from the signal change in a certain time interval of each channel. That is, the correlation between channels having similar signal changes in a certain time interval is high, and the correlation between channels having different ways of change is calculated to be low. Moreover, the channel pair selection part 12 can also divide | segment a frequency band into a subband, and can calculate the correlation between each channel for every subband.

  The channel pair selection unit 12 checks whether there is a channel pair having a correlation value higher than a predetermined threshold (step S5). Here, the predetermined threshold value is a threshold value for preventing a problem such as crosstalk that occurs when channels with low correlation are encoded as a pair, and can be appropriately set by those skilled in the art. For example, if the predetermined threshold is set high, the number of channels that are channel pair encoded decreases, so that the encoding efficiency is reduced but the sound quality deterioration due to crosstalk is reduced. On the other hand, if the predetermined threshold value is set low, the number of channels that are channel pair encoded increases, so that the encoding efficiency is improved, but sound quality deterioration due to crosstalk tends to occur. When there is a channel pair having a correlation value higher than the predetermined threshold (Yes in step S5), the channel pair selection unit 12 stores the channel name of the channel pair having the maximum correlation value in the channel name pair storage unit 133. The channel name of the channel pair is deleted from the channel name set in the channel name storage unit 131 (step S6).

  The channel pair selection unit 12 continues the processing of step S5 and step S6 until the number of channels stored in the channel name set of the channel name storage unit 131 becomes 1 or 0 (step S7).

  In step S5, there is no channel pair having a correlation value higher than the predetermined threshold (No in step S5), or the number of channels stored in the channel name set of the channel name storage unit 131 is 1 or 0 In the case (No in step S7), the channel pair selection unit 12 stores the channel currently stored in the channel name set of the channel name storage unit 131 in the single channel name storage unit 132 as a channel to be subjected to single channel encoding. Store (step S8).

  When the processing by the channel pair selection unit 12 is completed, the signal distribution unit 14 outputs the channel stored in the single channel name storage unit 132 to the single channel encoding unit 20 and is stored in the channel name pair storage unit 133. The received channel is output to the channel pair encoder 30 (step S9).

  The single channel encoder 20 independently encodes the channels input from the channel distributor 10 channel by channel and outputs the result to the multiplexer 40.

  The channel pair encoding unit 30 collectively encodes the channel pairs input from the channel allocating unit 10 and outputs them to the multiplexing unit 40. Further, the channel pair encoding unit 30 outputs channel pair information indicating a channel to be a channel pair to the multiplexing unit 40.

  The multiplexing unit 40 multiplexes the encoded acoustic signal data (encoded data) from the single channel encoding unit 20 and the channel pair encoding unit 30 and the channel pair information from the channel pair encoding unit 30. To generate a single stream (ES: Elementary Stream) for transmission to another device. For example, the multiplexing unit 40 can add channel pair information to the encoded data as metadata for each frame to generate a transmission stream.

  As described above, according to the present embodiment, the channel allocating unit 10 includes a channel that encodes each channel with a single channel based on the correlation between the channels included in the multi-channel acoustic signal, and two channel pairs. It distributes to the channel to be encoded, the encoding unit (single channel encoding unit 20 and channel pair encoding unit 30) performs encoding according to the allocation result, and the multiplexing unit 40 encodes each channel One stream is generated by multiplexing data and channel pair information indicating a channel to be encoded with two channel pairs. This makes it possible to select single channel coding or channel pair coding based on the correlation between the channels included in the multichannel acoustic signal. In other words, highly correlated channels can be channel pair encoded and other channels can be single channel encoded, so that the original bit quality of the multi-channel acoustic signal can be maintained and the required bit rate can be suppressed. Become. In addition, depending on the characteristics of the multi-channel acoustic signal, whether each channel is single-channel encoded or channel pair encoded changes. For example, the encoding method is a channel like the conventional MPEG-2 AAC Annex. Therefore, it is possible to perform encoding more efficiently than a method predetermined for each.

  FIG. 4 is a functional block diagram of the acoustic signal decoding apparatus 2 according to an embodiment of the present invention. The acoustic signal decoding device 2 includes a separation unit 50 and a decoding unit 60.

  The separation unit 50 separates the encoded data and the channel pair information from the input stream and outputs each to the decoding unit 60. The encoded data is a set of encoded data of a channel that has been subjected to single channel encoding and encoded data of a channel that has been subjected to channel pair encoding, and the separation unit 50 separates each encoded data. And output to the decoding unit 60. Further, as described above, the channel pair information indicates a channel pair-encoded channel.

  The decoding unit 60 decodes the encoded data according to the channel pair information, and generates a multi-channel acoustic signal. More specifically, the decoding unit 60 performs decoding corresponding to the channel pair encoding on the encoded data of the channel pair-encoded based on the channel pair information, and encodes the encoded data of other channels. Performs decoding corresponding to single channel coding. A multi-channel acoustic signal is generated by decoding each channel by the decoding unit 60.

  Thus, according to the present embodiment, the separation unit 50 separates the encoded data of each channel and the channel pair information from the input signal, and the decoding unit 60 determines the channel pair based on the channel pair information. The encoded data of the encoded channel is decoded corresponding to channel pair encoding, and the encoded data of other channels is decoded corresponding to single channel encoding. Thereby, it becomes possible to decode the acoustic signal encoded by the acoustic signal encoding device 1 according to the present invention.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each functional unit, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of functional units, steps, etc. can be combined into one or divided. It is.

  For example, the channel distribution unit 10 can perform distribution of each channel at predetermined time intervals or at least one of timings at which the multi-channel acoustic signal is switched. In other words, it is possible to perform coding with high coding efficiency and good sound quality by dynamically allocating channels without using the result of sorting once. Here, the predetermined time is determined by a person skilled in the art depending on indexes such as processing load (calculation processing load, calculation delay, etc.) related to channel allocation change and coding efficiency and sound quality improvement degree due to channel allocation change. It can be set appropriately. The timing at which the multi-channel acoustic signal is switched is, for example, a timing at which the characteristics (waveforms) of the preceding and following acoustic signals change greatly, and is preferably a timing at which all channels of the multi-channel acoustic signal become silent. This is because when all the channels of the multi-channel acoustic signal are silent, noise (discomfort during viewing) generated by changing the channel allocation does not occur.

  Moreover, in order to function as the acoustic signal encoding device 1, a computer can be suitably used, and such a computer is a program describing processing contents for realizing each function (step) of the acoustic signal encoding device 1. Is stored in a storage unit (not shown) of the computer, and this program is read out by a central processing unit (CPU) of the computer and each step is executed.

DESCRIPTION OF SYMBOLS 1 Acoustic signal encoding apparatus 10 Channel distribution part 11 Signal storage part 12 Channel pair selection part 13 Channel information storage part 131 Channel name storage part 132 Single channel name storage part 133 Channel name pair storage part 14 Signal distribution part 20 Single Channel encoding unit 30 Channel pair encoding unit 40 Multiplexing unit 2 Acoustic signal decoding unit 50 Separating unit 60 Decoding unit

Claims (4)

An acoustic signal encoding device for encoding an acoustic signal of a multi-channel acoustic system,
A channel distribution unit that distributes each channel into a channel that is encoded with a single channel and a channel that is encoded with two channel pairs based on the correlation between the channels included in the acoustic signal;
According to the distribution result, an encoding unit that encodes each channel with a single channel or 2 channel pairs;
An acoustic signal encoding apparatus comprising: a multiplexing unit that multiplexes the encoded data of each channel and channel pair information indicating a channel to be encoded by two channel pairs.   The acoustic signal encoding device according to claim 1, wherein the channel distribution unit performs the distribution of each channel at predetermined time intervals or at least one of timings at which the acoustic signal is switched. An acoustic signal encoding method by an acoustic signal encoding device that encodes an acoustic signal of a multi-channel acoustic system,
The processing procedure by the acoustic signal encoding device is as follows:
Allocating each channel to a channel that is encoded by a single channel and a channel that is encoded by a two-channel pair based on the correlation between the channels included in the acoustic signal;
Encoding each channel with a single channel or 2 channel pairs according to the distribution result;
A method of encoding an acoustic signal, comprising: multiplexing encoded data of each channel and channel pair information indicating a channel to be encoded with a two-channel pair. An acoustic signal decoding apparatus for decoding an acoustic signal of a multi-channel acoustic system,
A separation unit that separates, from an input signal, encoded data of each channel included in the acoustic signal and channel pair information indicating a channel encoded by two channel pairs;
Based on the channel pair information, the encoded data of the channel encoded by the two channel pairs is decoded corresponding to the encoding of the two channel pairs, and the encoded data of the other channels is encoded by a single channel. An audio signal decoding device comprising: a decoding unit that performs decoding corresponding to the above.

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