KR100923156B1 - System and Method for Encoding and Decoding for multi-channel audio - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

A multichannel audio encoding and decoding system and method.

2. Technical problem to be solved by the invention

Provided are a multichannel audio encoding and decoding system and method for decoding a multichannel audio signal while simultaneously improving sound quality.

3. Summary of Solution to Invention

A bitstream demultiplexer for demultiplexing the multiplexed bitstream as an input signal into a multichannel audio bitstream having a low sampling frequency, a spatial audio coding (SAC) bitstream, and a spectra band replication (SBR) bitstream; A multichannel audio decoder for decoding the multichannel audio bitstream and outputting a downmix signal and a multichannel audio signal; An SBR decoding unit for decoding the downmix signal and the SBR bitstream by an SBR method and outputting a downmix signal in which a high frequency region is restored; And a SAC decoding unit for outputting a multi-channel audio signal having a high sampling frequency by decoding the multi-channel audio signal using a spatial cue included in the SAC bitstream and a downmix signal from which the high frequency region is restored by the SAC method. .

4. Important uses of the invention

Used to encode and decode multichannel audio signals.

Multichannel, Audio, Encoding, Decoding, SAC, SBR

Description

System and Method for Encoding and Decoding for multi-channel audio}

1 is a configuration diagram of an embodiment of a conventional stereo audio signal decoder;

2 is a configuration diagram of an embodiment of a conventional multi-channel audio signal decoder;

3 is a block diagram of a multi-channel audio decoding system according to an embodiment of the present invention;

4 is a detailed configuration diagram when AAC technology is applied to the multi-channel audio decoding unit of FIG. 3;

5 is a block diagram of a multi-channel audio encoding system according to an embodiment of the present invention;

FIG. 6 is a detailed configuration diagram when AAC technology is applied to the multichannel audio encoding unit of FIG. 5. FIG.

7 is a diagram illustrating an embodiment of a multichannel audio bitstream in accordance with the present invention.

8 is a flowchart illustrating a decoding process performed in the multichannel audio decoding system of FIG. 3.

9 is a flowchart illustrating an encoding process performed in the multichannel audio encoding system of FIG. 5.

The present invention relates to a multi-channel audio encoding and decoding system and method, and more particularly, by using SAC (Spatial Audio Coding) and SBR (Spectral Band Replication), high quality multi A method of encoding and decoding a channel audio signal.

1 is a configuration diagram of an embodiment of a conventional stereo audio signal decoder.

As shown in FIG. 1, the MPEG-1 Audio Layer II decoder 101 decodes only an MPEG-1 Layer II bitstream from an MPEG-2 Layer II bitstream as an input signal and outputs a stereo audio signal. The conventional stereo audio signal decoder can provide a high quality audio signal while supporting various sampling frequencies of 24 kHz, 32 kHz, 44.1 kHz, and 48 kHz, but has a disadvantage in that it cannot decode a multi-channel signal.

2 is a diagram illustrating an embodiment of an audio signal decoder in a conventional multichannel DAB receiver.

As shown in FIG. 2, the MPEG-2 Audio Layer II decoder 201 outputs a multichannel audio signal from an MPEG-2 Layer II bitstream as an input signal.

Meanwhile, according to the DAB standard, a multichannel audio signal is sampled at 1/2 of a sampling frequency for a stereo audio signal. Therefore, when the audio signal according to the DAB standard is input to the multi-channel audio signal decoder 201 of FIG. 2, the multi-channel audio signal and the stereo audio signal are downsampled to 1/2 compared to the stereo signal and the sound quality is degraded. There are disadvantages.

The present invention has been proposed to solve the above problems, and an object thereof is to provide a multichannel audio encoding and decoding system and method for decoding a multichannel audio signal and simultaneously improving sound quality.

The present invention for achieving the above object, in the multi-channel audio decoding system, the multiplexed bitstream that is the input signal is a multi-channel audio bitstream and SAC (Spatial Audio Coding) bitstream and SBR (Spectral Band Replication) of low sampling frequency A bitstream demultiplexer for demultiplexing into a bitstream; A multichannel audio decoder for decoding the multichannel audio bitstream and outputting a downmix signal and a multichannel audio signal; An SBR decoding unit for decoding the downmix signal and the SBR bitstream by an SBR method and outputting a downmix signal in which a high frequency region is restored; And a SAC decoding unit which decodes the multichannel audio signal by the SAC method using a spatial cue included in the SAC bitstream and the downmix signal from which the high frequency region is restored, and outputs a multichannel audio signal having a high sampling frequency. .

The present invention also provides a multichannel audio encoding system comprising: a downsampling unit for downsampling a sampling frequency of a multichannel audio signal having a high sampling frequency as an input signal; A multichannel audio encoding unit for encoding the downsampled multichannel audio signal and outputting the multichannel audio bitstream; A SAC encoder for outputting a SAC bitstream and a downmix signal by encoding the input multi-channel audio signal using a SAC scheme; An SBR encoding unit for outputting an SBR bitstream by encoding the multichannel audio signal, which is the input signal, by using the downmix signal output from the SAC encoder; And a bitstream multiplexer configured to multiplex the multichannel audio bitstream, the SAC bitstream, and the SBR bitstream.

In addition, the present invention for achieving the above object, in the multi-channel audio decoding method, the multiplexed bitstream that is the input signal multi-channel audio bitstream and SAC (Spatial Audio Coding) bitstream and SBR (Spectral) Band Replication) a bitstream demultiplexing step of demultiplexing into a bitstream; A multichannel audio decoding step of decoding the multichannel audio bitstream to output a downmix signal and a multichannel audio signal; An SBR decoding step of decoding the downmix signal and the SBR bitstream in an SBR manner and outputting a downmix signal in which a high frequency region is restored; And a SAC decoding step of outputting a multi-channel audio signal having a high sampling frequency by decoding the multi-channel audio signal by a SAC method using a spatial cue included in the SAC bitstream and a downmix signal from which the high frequency region is restored. do.

The present invention also provides a multichannel audio encoding method comprising: a downsampling step of downsampling a sampling frequency of a multichannel audio signal having a high sampling frequency as an input signal; A multichannel audio encoding step of encoding the downsampled multichannel audio signal and outputting the multichannel audio bitstream; A SAC encoding step of encoding the input multi-channel audio signal by the SAC method and outputting a SAC bitstream and a downmix signal; An SBR encoding step of outputting an SBR bitstream by encoding the multichannel audio signal, which is the input signal, by using the downmix signal output by the SAC encoding step by an SBR method; And a bitstream multiplexing step of multiplexing the multichannel audio bitstream, the SAC bitstream, and the SBR bitstream.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of a multi-channel audio decoding system according to an embodiment of the present invention.

As shown in FIG. 3, the multichannel audio decoding system according to the present invention includes a bitstream de-multiplexer 301, a multichannel audio decoding unit 303, an SBR decoding unit 305, and a SAC decoding. A portion 307 is included.

The multiplexed bitstream, which is an input signal of the decoding system according to the present invention, is a bitstream in which a multichannel audio bitstream, an SBR bitstream, and a SAC bitstream are multiplexed at a low sampling frequency (Fs, for example, 24 kHz). The generation of such multiplexed bitstreams is described in the multichannel audio encoding system according to the present invention. The multiplexed bitstream may be a DAB audio signal.

The bitstream demultiplexer 301 extracts a SAC bitstream and an SBR bitstream from the multiplexed bitstream as the input signal.

The multichannel audio decoding unit 303 decodes the multiplexed bitstream as the input signal and outputs a stereo or mono downmix signal having a low sampling frequency (eg, 24 kHz) and a multichannel audio signal.

When the multichannel audio bitstream is an MPEG-2 Layer II bitstream or an AAC bitstream, the multichannel audio decoding unit 303 uses MPEG-2 Audio Layer II decoding technology or AAC (Advanced Audio Coding) decoding technology. Can be.

The SBR decoder 305 restores a high frequency region by using a stereo or mono downmix signal output from the multichannel audio decoder 303 and an SBR bitstream extracted from the bitstream demultiplexer 301. Decode downmixed stereo or mono signals (e.g., Fs = 48kHz).

SBR (Spectral Band Replication) is a technique of restoring high frequency band components by analyzing low frequency band components of an audio signal. SBR is described in the international standard [ISO / IEC 14496-3 AMENDMENT 1: Bandwidth Extension].

The SAC decoding unit 307 may output a spatial cue included in the SAC bitstream extracted from the bitstream demultiplexing unit 301 and a downmix stereo or mono signal output from the SBR decoding unit 305. By extracting and controlling information about the audio signal using the multi-channel audio signal having a low sampling frequency (eg, 24 kHz) output from the multi-channel audio decoding unit 303, a high sampling frequency (eg, 48 kHz) into a multichannel audio signal.

SAC (Spatial Audio Coding) is a method of representing, transmitting, and restoring a multichannel audio signal as a downmixed mono or stereo signal and spatial cue information to transmit high quality multichannel audio signals at low bit rates.

A method for decoding a multichannel audio signal using the spatial cue parameter included in the stereo or mono downmix signal and the SAC bitstream is described by Baumgarte and Faller (C. Faller and F. Baumgarte, “Binaural Cue”). Coding applied to stereo and multi-channel audio compression, ”112th AES Convention, Munich, prepreint 5574, May 3002) or MPEG Surround standards (ISO / IEC JTC1 / SC29 / WG11, N7947, ISO / IEC 23003-1: 3006 / FCD , MPEG Surround, Jan., 3006) can be applied, and thus it is possible to decode a multi-channel audio signal that is acoustically indistinguishable from the original sound.

FIG. 4 is a detailed configuration diagram when AAC technology is applied to the multichannel audio decoding unit 303 of FIG. 3.

AAC (Advanced Audio Coding) is an audio signal compression method used in MPEG-2 or MPEG-4. It has a high compression ratio and no sound quality deterioration compared to MPEG-1, and has a feature that can cope with various bands and many channels. .

As shown in FIG. 4, the multichannel audio decoding unit 303 includes an AAC decoder 401 and a channel remixer 403.

The AAC decoder 401 is a stereo or mono downmix signal having a low sampling frequency (eg, 24 kHz) and a multi-channel from the multichannel audio bitstream (AAC bitstream) output from the bitstream demultiplexer 301. Decode the channel (LO, RO, T, Q1, Q2) audio signals.

The channel remixer 403 converts the multichannel (LO, RO, T, Q1, Q2) audio signals decoded from the AAC decoder 401 into a multichannel (L, R, C, Ls, Rs) audio signal. The mixture is transferred to the SAC decoding unit 307.

The multiplexed bitstream input to the multichannel audio decoding system of FIG. 3 is generated by the multichannel audio encoding system according to the present invention as described below.

5 is a block diagram of a multichannel audio encoding system according to an embodiment of the present invention.

As shown in FIG. 5, the multichannel audio encoder system according to the present invention includes a downsampling unit 501, a multichannel audio encoding unit 503, an SAC encoding unit 505, an SBR encoding unit 507, and a bitstream. The multiplexer 509 is included.

The downsampling unit 501 outputs a multichannel audio signal (for example, Fs = 24kHz) by downsampling a sampling frequency of a multichannel audio signal (for example, Fs = 48kHz) that is an input signal by 1/2 times. do.

The multichannel audio encoding unit 503 encodes a multichannel audio signal (for example, Fs = 24kHz) output from the downsampling unit 501 into a multichannel audio bitstream, and performs stereo (or Mono) to generate a downmix signal (e.g., Fs = 24 kHz).

The multichannel audio encoding unit 303 may use MPEG-2 Audio Layer II encoding technology or AAC encoding technology. In this case, the multichannel audio bitstream is an MPEG-2 Layer II bitstream or an AAC bitstream. .

The SAC encoder 505 extracts and encodes a spatial cue parameter from a multichannel audio signal as an input signal to generate a SAC side information bitstream, and generates a stereo (or mono) downmix from the multichannel audio signal. Generate a signal. In this case, the spatial cue parameter constituting the SAC side information bitstream includes only high frequency components canceled during the downsampling process of the downsampling unit 501.

The multichannel audio encoding unit 503 and the SAC encoding unit 505 downmix a multichannel (for example, 5.1 channel) signal L, R, C, Ls, Rs, Lfe to stereo (or mono). How to ITU-R BS. Same as the method defined in 775-1 and downmixed based on Equation 1 below.

In this case, L0 and R0 are stereo downmix signals, L and R are left and right main channels, C (center) is a center channel, Ls (left surround) is a left surround channel, and Rs (right surround) is a right surround channel. (5.1 channel)

The SBR encoding unit 507 uses a stereo (or mono) downmix signal output from the SAC encoding unit 505 and a stereo (or mono) downmix signal output from the multichannel audio encoding unit 503. Create an SBR bitstream.

The bitstream multiplexer 509 is a multichannel audio bitstream output from the multichannel audio encoder 503 and an SAC side information bitstream output from the SAC encoder 505 and the SBR encoder 507. A multiplexed bitstream is generated by multiplexing the SBR bitstream output from the multiplexer.

The multiplexed bitstream may be a DAB audio signal.

FIG. 6 is a detailed configuration diagram when AAC technology is applied to the multi-channel audio encoding unit 503 of FIG. 5.

As shown in FIG. 6, the multichannel audio encoding unit 503 includes a channel mixer 601 and an AAC encoder 603.

The channel mixer 601 outputs the multichannel audio signals L, R, C, Ls, and Rs output from the downsampling unit 501 according to Equation 1 and Equation 2 below. The multichannel audio signals LO, RO, T, Q1, and Q2 are mixed and output.

In this case, C (center) is the center channel, Ls (left surround) is the left surround channel, Rs (right surround) is the right surround channel, T, Q1, Q2 are the remaining multi-channel signals except for the stereo downmix signal. (5.1 channel)

The AAC encoder 603 encodes the multichannel audio signal output from the channel mixer 601 into an AAC bitstream, and generates a stereo or mono downmix signal in the encoding process.

7 is a diagram illustrating an embodiment of a multichannel audio bitstream according to the present invention, in which a multichannel audio signal, an SBR bitstream, and a SAC bitstream, which are half-sampled and encoded in the MPEG-2 Layer II standard, are added. The bitstream configuration diagram when multiplexing the data area (Ancillary Data).

As shown in FIG. 7, the multi-channel audio signals T, Q1, and Q2 encoded by MPEG-2 Layer II after 1/2 down-sampling are multiplexed into an Ancillary Data 1 region, and a high frequency region of the downmix stereo signal. The SBR bitstream encoded by the multiplexer is multiplexed into an Ancillary Data 2 region, and the SAC bitstream, which is multichannel encoded information, is multiplexed into an Ancillary Data 3 region.

8 is a flowchart illustrating a decoding process performed in the multichannel audio decoding system of FIG. 3.

As illustrated in FIG. 8, the bitstream demultiplexer 301 extracts an SAC bitstream and an SBR bitstream from the multiplexed bitstream that is the input signal (801).

The multichannel audio decoding unit 303 decodes the multiplexed bitstream as the input signal and outputs a stereo or mono downmix signal having a low sampling frequency and a multichannel audio signal (803).

The SBR decoder 305 restores a high frequency region by using a stereo or mono downmix signal output from the multichannel audio decoder 303 and an SBR bitstream extracted from the bitstream demultiplexer 301. Decode the downmix stereo or mono signal (805).

The SAC decoding unit 307 may output a spatial cue included in the SAC bitstream extracted from the bitstream demultiplexing unit 301 and a downmix stereo or mono signal output from the SBR decoding unit 305. By extracting and controlling information on the audio signal using the multichannel audio decoding unit 303, the multichannel audio signal having the low sampling frequency is decoded into the multichannel audio signal having the high sampling frequency (807). .

9 is a flowchart illustrating an encoding process performed in the multichannel audio encoding system of FIG. 5.

As illustrated in FIG. 9, the downsampling unit 501 outputs a multichannel audio signal by downsampling a sampling frequency of a multichannel audio signal that is an input signal by a factor of 1/2 (operation 901).

The SAC encoder 505 extracts and encodes a spatial cue parameter from a multichannel audio signal as an input signal to generate a SAC side information bitstream, and generates a stereo (or mono) downmix from the multichannel audio signal. Generate a signal (903).

The multichannel audio encoding unit 503 encodes the multichannel audio signal output from the downsampling unit 501 into a multichannel audio bitstream and generates a stereo (or mono) downmix signal in the encoding process ( 905).

The SBR encoding unit 507 uses a stereo (or mono) downmix signal output from the SAC encoding unit 505 and a stereo (or mono) downmix signal output from the multichannel audio encoding unit 503. A SBR bitstream is generated (907).

The bitstream multiplexer 509 is a multichannel audio bitstream output from the multichannel audio encoder 503 and an SAC side information bitstream output from the SAC encoder 505 and the SBR encoder 507. The multiplexed SBR bitstream is multiplexed to generate a multiplexed bitstream (909).

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

Since the present invention provides a mono or stereo downmix signal, it is possible to provide a high quality multichannel audio service supporting a sampling frequency of 48 kHz while maintaining compatibility with conventional mono, stereo and multichannel audio receivers. In addition, the SBR and SAC technology enables encoding and decoding of multichannel audio signals with improved sound quality while reducing bitrate.

Claims (22)

In a multichannel audio decoding system, A bitstream demultiplexer for demultiplexing a multiplexed bitstream of a DAB scheme as an input signal into a spatial audio coding (SAC) bitstream and a spectra band replication (SBR) bitstream; A multichannel audio decoder for decoding the multiplexed bitstream and outputting a downmix signal and a multichannel audio signal; An SBR decoding unit for decoding the downmix signal and the SBR bitstream by an SBR method and outputting a downmix signal in which a high frequency region is restored; And SAC decoding unit for outputting a multi-channel audio signal of a high sampling frequency by decoding the multi-channel audio signal by the SAC method using the spatial cue included in the SAC bitstream and the downmix signal from which the high frequency region is restored Multichannel audio decoding system comprising a. delete The method of claim 1, The multichannel audio decoding unit An AAC decoder for decoding the multichannel audio bitstream and outputting the downmix signal and the multichannel audio signal; And The channel remixer for remixing the channels of the multi-channel audio signal decoded from the AAC decoder and outputs to the SAC decoding unit Multichannel audio decoding system comprising a. The method of claim 1, The downmix signal is Which can be either stereo or mono Multichannel Audio Decoding System. In a multichannel audio encoding system, A downsampling unit for downsampling a sampling frequency of a multichannel audio signal having a high sampling frequency as an input signal; A multichannel audio encoding unit for encoding the downsampled multichannel audio signal and outputting the multichannel audio bitstream; A SAC encoder for outputting a SAC bitstream and a downmix signal by encoding the input multi-channel audio signal using a SAC scheme; An SBR encoding unit for outputting an SBR bitstream by encoding the multichannel audio signal, which is the input signal, by using the downmix signal output from the SAC encoder; And A bitstream multiplexer for outputting a DAB multiplexed bitstream for multiplexing the multichannel audio bitstream, the SAC bitstream, and the SBR bitstream. Multichannel audio encoding system comprising a. The method of claim 5, The multichannel audio encoding unit A channel mixer for mixing channels of the downsampled multichannel audio signal; And AAC encoder for decoding the multi-channel audio signal output from the channel mixer and outputs the multi-channel audio bitstream Multichannel audio encoding system comprising a. The method of claim 5, The multichannel audio encoding unit Further outputting a downmix signal by encoding the downsampled multichannel audio signal, The SBR encoding unit Encoding a multichannel audio signal which is the input signal by further using a downmix signal output from the multichannel audio encoding unit Multichannel Audio Encoding System. The method according to claim 5 or 7, The downmix signal is Which can be either stereo or mono Multichannel Audio Encoding System. The method according to claim 5 or 7, The downmix signal is Generated by Equation 1 below Multichannel Audio Encoding System. [Equation 1]

In this case, L0 and R0 are stereo downmix signals, L and R are left and right main channels, C (center) is a center channel, Ls (left surround) is a left surround channel, and Rs (right surround) is a right surround channel. The method of claim 6, The channel mixer Mixing channels of the multichannel audio signal by Equation 2 below Multichannel Audio Encoding System. [Equation 2]

In this case, C (center) is the center channel, Ls (left surround) is the left surround channel, Rs (right surround) is the right surround channel, T, Q1, Q2 are the remaining multi-channel signals except stereo downmix signal. delete In the multi-channel audio decoding method, A bitstream demultiplexing step of demultiplexing a multiplexed bitstream of a DAB scheme as an input signal into a spatial audio coding (SAC) bitstream and a spectra band replication (SBR) bitstream; A multichannel audio decoding step of decoding the multiplexed multichannel audio bitstream to output a downmix signal and a multichannel audio signal; An SBR decoding step of decoding the downmix signal and the SBR bitstream in an SBR manner and outputting a downmix signal in which a high frequency region is restored; And SAC decoding step of outputting a multi-channel audio signal of a high sampling frequency by decoding the multi-channel audio signal by the SAC method using a spatial cue included in the SAC bitstream and the downmix signal from which the high frequency region is restored Multichannel audio decoding method comprising a. delete The method of claim 12, The multichannel audio decoding step An AAC decoding step of decoding the multichannel audio bitstream and outputting the downmix signal and the multichannel audio signal; And The channel remixing step of remixing channels of the multichannel audio signal decoded by the AAC decoding step and outputting the SAC decoding step Multichannel audio decoding method comprising a. The method of claim 12, The downmix signal is Which can be either stereo or mono Multichannel audio decoding method. In the multi-channel audio encoding method, A downsampling step of downsampling a sampling frequency of a multi-channel audio signal having a high sampling frequency as an input signal; A multichannel audio encoding step of encoding the downsampled multichannel audio signal and outputting the multichannel audio bitstream; A SAC encoding step of encoding the input multi-channel audio signal by the SAC method and outputting a SAC bitstream and a downmix signal; An SBR encoding step of outputting an SBR bitstream by encoding the multichannel audio signal, which is the input signal, by using the downmix signal output by the SAC encoding step by an SBR method; And A bitstream multiplexing step of outputting a DAB multiplexed bitstream by multiplexing the multichannel audio bitstream, the SAC bitstream, and the SBR bitstream Multi-channel audio encoding method comprising a. The method of claim 16, The multichannel audio encoding step A channel mixing step of mixing channels of the downsampled multichannel audio signal; And AAC encoder for decoding the multi-channel audio signal output by the channel mixing step and outputs the multi-channel audio bitstream Multi-channel audio encoding method comprising a. The method of claim 16, The multichannel audio encoding step Further outputting a downmix signal by encoding the downsampled multichannel audio signal, The SBR encoding step Encoding a multichannel audio signal which is the input signal by further using a downmix signal output by the multichannel audio encoding step Multichannel audio encoding method. The method according to claim 16 or 18, The downmix signal is Which can be either stereo or mono Multichannel audio encoding method. The method according to claim 16 or 18, The downmix signal is Generated by Equation 1 below Multichannel audio encoding method. [Equation 1]

In this case, L0 and R0 are stereo downmix signals, L and R are left and right main channels, C (center) is a center channel, Ls (left surround) is a left surround channel, and Rs (right surround) is a right surround channel. The method of claim 17, The channel mixing step Mixing the channels of the downsampled multichannel audio signal by Equation 2 Multichannel audio encoding method. [Equation 2]

In this case, C (center) is the center channel, Ls (left surround) is the left surround channel, Rs (right surround) is the right surround channel, T, Q1, Q2 are the remaining multi-channel signals except stereo downmix signal. delete

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