JP2015186143A - Channel number converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a channel number converter which can improve inconvenience when converting the number of channels of audio signals output from a plurality of audio channels more than 5.1 ch.SOLUTION: A channel number converter 1 for converting the number of channels of audio signals output from a plurality of audio channels includes a controller 10 which removes, when converting the number of channels of the audio signals output from the plurality of audio channels, a masked frequency component in audio signals of audio channels other than at least one predetermined channel selected from the plurality of audio channels by an audio frequency masking effect based on audio signals of the predetermined channel selected from the plurality of audio channels.

Description

  The present invention relates to a channel number conversion apparatus. More specifically, the present invention relates to an apparatus for converting the number of channels of a multi-channel audio signal (acoustic signal) exceeding, for example, 5.1 ch.

  In recent years, an acoustic system has been proposed that realizes highly realistic sound reproduction such as three-dimensional sound by using a large number of audio channels (see Patent Document 1 and Non-Patent Document 1). For example, a home theater system using an acoustic system such as 5.1ch surround has appeared for home use. For example, in Super Hi-Vision (SHV) broadcasting, 22.2 ch multi-channel sound is adopted.

  However, assuming use in homes, it is assumed that the number of speakers installed in each home is mostly smaller than the number of channels constituting the 22.2 ch multi-channel sound system.

  For this reason, in order to reproduce multi-channel sound such as 22.2ch at home, a technique for converting the number of channels to be small, such as downmixing, is required. Conventionally, a method for converting 5.1ch surround to 2ch stereo has been proposed (see Non-Patent Document 2, for example). However, the practical use of a method for converting the number of channels of a multi-channel acoustic system exceeding 5.1 ch is still desired.

  In general, the number of speakers installed in each home is not fixed. Further, as described above, the number of speakers installed in each home is usually not compatible with the 22.2 ch multi-channel sound system. For this reason, for example, when reproducing sound (sound) based on a multi-channel audio signal exceeding 5.1 ch, it is necessary to convert the number of channels of the audio signal in accordance with the number of installed speakers.

JP 2009-77379 A

IEICE Fundamentals Review Vol.3, No.4 (2010), pp.33-46 "Highly realistic acoustic technology and its theory" Akio Ando ARIB STD-B21 “Digital Broadcasting Receiver (Preferred Specifications)”

  However, if the number of channels is uniquely converted without depending on the provided content, various inconveniences are assumed.

  Accordingly, it is an object of the present invention to provide a channel number conversion device that improves the disadvantages of converting the number of audio signal channels of a plurality of audio channels exceeding 5.1 ch, for example.

The invention according to the first aspect to achieve the above object is
A channel number conversion device for converting the number of channels of audio signals of a plurality of audio channels,
When converting the number of audio signal channels of the plurality of audio channels,
The frequency component masked in the audio signal of the channel other than the predetermined channel among the plurality of audio channels is removed by the frequency masking effect of the audio based on the audio signal of at least one predetermined channel of the plurality of audio channels. The control part to perform is provided.

  In addition, the control unit may be configured such that the position or direction in which the channel for outputting the audio signal among the plurality of audio channels is arranged for the predetermined channel and channels other than the predetermined channel is the number of channels of the audio signal. The channel may be changed before and after conversion.

  The control unit may be configured to hold information for specifying the predetermined channel and a channel other than the predetermined channel.

  The control unit may identify the predetermined channel and a channel other than the predetermined channel based on information supplied from outside the channel number conversion device.

  The control unit may determine the predetermined channel and a channel other than the predetermined channel based on an audio frequency band based on an audio signal of each channel.

The invention according to the second aspect to achieve the above object is
A channel number conversion device for converting the number of channels of audio signals of a plurality of audio channels,
When converting the number of audio signal channels of the plurality of audio channels,
Due to the frequency masking effect of audio based on the audio signal of at least one predetermined channel among the plurality of audio channels, the frequency component masked in the audio signal of the channel other than the predetermined channel among the plurality of audio channels is removed. And a controller for converting the number of channels of the audio signal.

  According to the present invention, it is possible to provide a channel number conversion device that improves the inconvenience when converting the number of audio signal channels of a plurality of audio channels exceeding 5.1 ch, for example.

It is a functional block diagram explaining schematic structure of the channel number converter which concerns on embodiment of this invention. It is a figure explaining conversion of the number of channels in the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As described above, for example, various inconveniences are assumed when the number of audio signal channels of a plurality of audio channels exceeding 5.1 ch is uniquely converted without depending on the provided content.

  For example, when such conversion of the number of channels is performed, there arises a problem that the level is exceeded when adding audio signals. For this reason, in channel number conversion processing such as downmixing, it is common to perform downmixing after multiplying the audio signal before channel number conversion by a coefficient smaller than 1 so that the signal level does not overflow.

  However, if this is done, the loudness is greatly reduced, and there is a problem that the loudness is changed by changing the number of channels.

  Therefore, in the present invention, by utilizing the masking effect for each direction, the loudness before the channel number conversion is maintained after the conversion while preventing the signal level from overflowing at the time of the channel number conversion.

  FIG. 1 is a functional block diagram illustrating a schematic configuration of a channel number conversion apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the channel number conversion device 1 according to the present embodiment includes a control unit 10 and a storage unit 20. When an audio signal of a plurality of channels is input, the control unit 10 outputs a signal obtained by converting the number of channels of the audio signal. In FIG. 1, an audio signal of 22.2 ch is input from the left side of the channel number conversion device 1, and an audio signal with the channel number converted, such as 5.1 ch, is output from the left side of the channel number conversion device 1. It shows how it is done.

  Hereinafter, description will be made assuming that the channel number conversion apparatus 1 according to the present invention includes the control unit 10 and the storage unit 20. However, the present invention is not limited to such an embodiment. For example, various configurations such as a configuration in which the control unit 10 includes the storage unit 20, or the channel number conversion device 1 is configured as a system-on-chip (SoC) having the functions of the control unit 10 and the storage unit 20. Can be assumed.

  The control part 10 can be comprised including arbitrary processing apparatuses, such as a processor or a microcomputer, for example. In this embodiment, the control part 10 analyzes the said data based on the input of the various data containing an audio | voice signal, or performs various arithmetic processing. Moreover, the control part 10 can memorize | store various analysis results in the memory | storage part 20 as needed, and can read the various information memorize | stored in the memory | storage part 20 as needed. In particular, in the present embodiment, when an audio signal of a plurality of channels is input, the control unit 10 performs a process of converting the number of channels of the audio signal. In the present embodiment, the control unit 10 also performs various processes related to the conversion of the number of channels. The processing performed by the control unit 10 in the present embodiment will be further described later.

  The channel number conversion device 1 according to the present embodiment distributes audio signals of a plurality of audio channels based on information on masker channels of audio signals when converting the number of channels. For this reason, as shown in FIG. 1, the control unit 10 is supplied with information on the masker channel of the audio signal.

  The storage unit 20 can be configured to include any memory device. The storage unit 20 also stores an algorithm used when the control unit 10 performs data analysis and various arithmetic processes as described above, and various reference tables such as a lookup table (LUT).

  As described above, the channel number conversion device 1 according to the present embodiment converts the number of channels of the audio signal based on the input of the audio signals of a plurality of channels and outputs the converted signal. Here, the number of channels of the audio signal handled by the channel number conversion apparatus 1 is not particularly limited, and any number of channels can be used. However, the channel number conversion device 1 according to the present embodiment is particularly suitable for handling multi-channel audio signals exceeding 5.1 ch. In the following description, the case where the audio signal input to the channel number conversion apparatus 1 is, for example, a 22.2 ch surround audio signal employed in SHV will be described. Here, the 22.2 ch audio signal input to the channel number conversion device can be a signal of various formats such as a PCM signal or a compression-coded signal.

  That is, in the present embodiment, the position where the speaker is arranged in the acoustic system that reproduces audio based on the 22.2 ch audio signal is defined in the standard SMPTE ST2036-2-2-2008. In the SHV acoustic system, in a three-dimensional space centered at the listening position, ten speakers are arranged in the middle layer of ch1-12, nine speakers are arranged in the upper layer (Top) of ch13-21, and ch22 Three speakers are arranged in the lower layer (Bottom) of ˜24. Note that channels 4 and 10 are channels for low-frequency sound effects (LFE). In this way, in the 22.2 ch acoustic system, audio based on the audio signals of a total of 24 ch channels is reproduced.

  Next, in the channel number conversion apparatus 1 according to the present embodiment, processing when converting the number of channels based on input of audio signals of a plurality of channels will be described. In the following description, as an example, the channel number conversion device 1 will describe a case where a 22.2 ch surround sound signal is converted to 5.1 ch (downmix).

  FIG. 2 is a diagram for explaining the conversion of the number of channels in an embodiment of the present invention. FIG. 2 shows the flow of processing when the channel number conversion apparatus 1 receives audio signals of a plurality of audio channels, converts the number of channels of the audio signals, and outputs the converted audio signals, from left to right. ing.

  When a 22.2ch audio signal is input to the channel number conversion device 1, the control unit 10 converts the input 22.2ch audio signal into at least one predetermined channel and a channel other than the predetermined channel. (Step S11).

  In the present embodiment, the frequency components to be masked, that is, the portions unnecessary for hearing in each channel are excluded by using the masking effect of the predetermined channel with respect to other channels, and downmixing is performed. Hereinafter, a predetermined channel on the masking side is referred to as a “masker channel”, and another channel on the masked side is referred to as a “masky channel”. That is, in step S11, the control unit 10 distributes the 22.2ch audio signal to at least one masker channel and at least one masky channel.

  In the present embodiment, selection of a masker channel is important when calculating the frequency masking effect of audio based on the audio signal of the channel. Hereinafter, in step S11, an example in which 5ch of FL, FC, FR, BL, BR among the 10.2ch of the middle layer (ch1 to 12) defined in the standard SMPTE ST2036-2-2-2008 is used as a masker channel will be described. .

  Further, in the following description, information for determining which channel of 22.2ch is to be a masker channel will be described as an example of a configuration supplied from the outside of the control unit 10. However, the channel number conversion device 1 may be configured to hold masker channel information in the storage unit 20, for example.

  When the channel is distributed in step S11, the control unit 10 converts the number of channels for the masker channel among the distributed channels (step S12).

  The channel number conversion in step S12 is a method of rendering a three-dimensional channel arrangement into a desired channel arrangement / number in addition to channel number conversion by a fixed downmix coefficient similar to 5.1ch (for example, A. Ando and K. Hamasaki, “Sound intensity based three-dimensional panning,” AES Convention, Convention Paper 7675 (2009), etc.) can be used.

  Further, when the channel is distributed in step S11, the control unit 10 performs a first process of removing unnecessary frequency components for the masky channel among the distributed channels (step S13). In step S13, the control unit 10 uses the 22.2ch sound channel arrangement, and the frequency component that is not psychoacoustically unnecessary according to the masking effect (direction-specific masking effect) that the masker channel exerts on the other musky channels. Remove.

  The conventional masking effect takes into account the interaction in a plurality of sounds coming from the same direction. However, in the case of incoming sounds from different directions, the manifestation of interaction changes psychologically, so such a case is considered in the direction-specific masking effect.

  In step S13, it is not essential to consider the masking effect of all masker channels. For example, various processes such as considering only the influence of the nearest masker channel can be performed. Further, when removing unnecessary frequency components by masking, for example, in the case of a compression-encoded signal, it is effective to perform processing for each band component by MDCT (modified cosine transform) encoding. is there.

  When unnecessary frequency components are removed in step S13, the control unit 10 performs a second process for removing unnecessary frequency components for the masky channel (step S14). In step S14, the control unit 10 is psychoacoustic in accordance with the masking effect (direction-specific masking effect) that the masker channel exerts on the other masky channels in the channel arrangement after the channel number conversion (5.1ch). Remove unnecessary frequency components. In step S14, it is possible to appropriately select which masker channel the masking effect is taken into consideration.

  In step S14, direction-specific masking is considered again at the position or direction after the masker channel predetermined in 22.2ch is converted. Therefore, for example, when the location of the masker channel does not change before and after the channel number conversion as in the middle layer channel FC (Front center), processing is performed as sound from the same direction. On the other hand, when the location of the masker channel changes before and after the channel number conversion, for example, in the upper layer channel TpFC (Top front center), the processing is performed with the information of the converted location.

  When unnecessary frequency components are removed in step S14, the control unit 10 converts the number of channels for the masky channel among the distributed channels (step S15). In step S15, the same processing as the channel number conversion in step S12 can be performed.

  When the number of channels is converted for the masker channel and the maskee channel in step S12 and step S15, the control unit 10 adds the respective audio signals (step S16). After step S16, the channel number conversion device 1 can output an audio signal obtained by converting the number of channels from 22.2ch to 5.1ch.

  Thus, in this embodiment, the channel number conversion apparatus 1 converts the number of audio signal channels of a plurality of audio channels (for example, 22.2 ch) (for example, to a small number of channels such as 5.1 ch). Here, when the control unit 10 converts the number of audio signals of a plurality of audio channels, the control unit 10 converts an audio frequency based on an audio signal of at least one predetermined channel among the plurality of audio channels. Due to the masking effect, frequency components masked in the audio signals of channels other than the predetermined channel among the plurality of audio channels are removed. Further, at least one predetermined channel of the plurality of audio channels can be the masker channel described above, and a channel other than the predetermined channel among the plurality of audio channels is the above-described masky channel. Can do. Further, in the present embodiment, the above-described masker channel can be, for example, a channel including a dialog signal or an object channel.

  In the present embodiment, the masker channel and the maskee channel are channels in which the position or direction of a channel that outputs an audio signal among a plurality of audio channels is changed before and after the number of channels of the audio signal is converted. can do.

  In the present embodiment, the control unit 10 may be configured to hold information for specifying the masker channel and the maskee channel in, for example, the storage unit 20. Further, in the present embodiment, the control unit 10 may specify the masker channel and the maskee channel based on information supplied from the outside of the channel number conversion device 1. In the present embodiment, the control unit 10 may determine the masker channel and the maskee channel based on the audio frequency band based on the audio signal of each channel.

  As described above, in the present embodiment, when downmixing is performed, a masking effect that a predetermined main channel (for example, a masker channel) exerts on other channels (for example, a masky channel) is used to make a masky component ( Exclude audible unnecessary components in each channel).

  Therefore, according to the channel number conversion device according to the present embodiment, when converting the number of channels of an acoustic system having a plurality of audio channels, the loudness before conversion is maintained after conversion while preventing overflow of the signal level. be able to.

  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 changes and modifications 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 means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of functional units, steps, etc. are combined or divided into one. It is possible. Further, the above-described embodiments of the present invention are not limited to being implemented faithfully to the embodiments described above, and may be implemented by appropriately combining the features or omitting some of them. it can.

  In the above-described embodiment, an apparatus for converting a 22.2 ch multi-channel audio signal employed in SHV into a small number of channels has been described, but the present invention is not limited to such an embodiment. The present invention can be implemented not only in the 22.2 channel multi-channel adopted in SHV but also in other channel-based stereophonic audio formats. Further, the present invention can be applied to an object-based method such as Dolby ATMOS or a scene-based method such as higher-order ambisonics, in addition to the above-described channel-based method such as 22.2ch.

  In the above-described embodiment, the first process for removing frequency components is performed in step S13, and the second process for removing frequency components is performed in step S14. However, the present invention is not limited to such an embodiment, and only one of step S13 and step S14 may be performed.

  In the above-described embodiment, the configuration in which both the frequency component removal process in step S13 and the frequency component removal process in step S14 are performed in the channel number conversion apparatus 1 has been described. However, the channel number conversion apparatus 1 according to the present invention may perform at least one of the frequency component removal processing of step S13 and step S14, for example, on the transmitter side in the SHV broadcasting station. In this case, the transmitter in the SHV broadcasting station transmits a broadcast wave obtained by compression-coding the audio signal that has been subjected to at least one of the frequency component removal processes in steps S13 and S14. In this case, the channel number conversion device 1 according to the present invention can immediately perform the channel number conversion in steps S12 and S15 after receiving the broadcast wave.

  Therefore, when converting the number of audio signals of a plurality of audio channels, the control unit 10 of the channel number conversion device 1 according to the present invention converts the number of audio signals of at least one predetermined channel among the plurality of audio channels. The number of channels of the audio signal from which the frequency component masked in the audio signal of the channel other than the predetermined channel is removed among the plurality of audio channels may be converted by the audio frequency masking effect based thereon.

  In this way, by performing unnecessary frequency component removal processing on the transmitter side, for example, an SHV receiver including a channel number conversion device does not need to perform frequency removal processing that requires a calculation amount. Therefore, in such a configuration, the configuration of the receiver can be simplified, which is advantageous for reducing the cost of the receiver.

  In the above-described embodiment, for convenience of explanation, the masker channel and the maskee channel are set in advance, and then the unnecessary frequency component is removed by the masking effect. In practice, however, there is a bidirectional relationship between the masker channel and the maskee channel. Further, when considering each frequency band, there may be a channel relationship in which the relationship between the masker channel and the maskee channel is switched. For this reason, the present invention can be configured to perform various processes in consideration of the masking effect between all the channels for each frequency band.

1 Channel Number Conversion Device 10 Control Unit 20 Storage Unit

Claims (6)

A channel number conversion device for converting the number of channels of audio signals of a plurality of audio channels,
When converting the number of audio signal channels of the plurality of audio channels,
The frequency component masked in the audio signal of the channel other than the predetermined channel among the plurality of audio channels is removed by the frequency masking effect of the audio based on the audio signal of at least one predetermined channel of the plurality of audio channels. A channel number conversion device including a control unit.   The control unit converts the number of channels of the audio signal according to a position or a direction in which the channel for outputting the audio signal among the plurality of audio channels is arranged in the predetermined channel and a channel other than the predetermined channel. The channel number conversion device according to claim 1, wherein the channel is changed before and after.   The channel number conversion device according to claim 1, wherein the control unit is configured to hold information for specifying the predetermined channel and a channel other than the predetermined channel.   The channel number conversion device according to claim 1 or 2, wherein the control unit specifies the predetermined channel and a channel other than the predetermined channel based on information supplied from outside the channel number conversion device. .   The channel number conversion device according to claim 1, wherein the control unit determines the predetermined channel and a channel other than the predetermined channel based on a frequency band of audio based on an audio signal of each channel. A channel number conversion device for converting the number of channels of audio signals of a plurality of audio channels,
When converting the number of audio signal channels of the plurality of audio channels,
Due to the frequency masking effect of audio based on the audio signal of at least one predetermined channel among the plurality of audio channels, the frequency component masked in the audio signal of the channel other than the predetermined channel among the plurality of audio channels is removed. A channel number conversion device comprising a control unit for converting the number of channels of the audio signal.

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