公开(公告)号：US09722578B2

公开(公告)日：2017-08-01

申请号：US15353914

申请日：2016-11-17

Applicant: Dolby International AB

Inventor： Per Ekstrand

IPC: G06F17/10 ,  H03H17/02 ,  G10L21/00 ,  G10L19/02 ,  G10L19/26 ,  H04R3/04

CPC classification number: H04R3/04 ,  G06F17/10 ,  G06F17/11 ,  G10L19/008 ,  G10L19/0204 ,  G10L19/0208 ,  G10L19/26 ,  G10L19/265 ,  G10L21/00 ,  H03H17/0201 ,  H03H17/0248 ,  H03H17/0266 ,  H03H17/0275 ,  H03H17/0294 ,  H03H2017/0297 ,  H04S7/307

Abstract: The document relates to modulated sub-sampled digital filter banks, as well as to methods and systems for the design of such filter banks. In particular, the present document proposes a method and apparatus for the improvement of low delay modulated digital filter banks. The method employs modulation of an asymmetric low-pass prototype filter and a new method for optimizing the coefficients of this filter. Further, a specific design for a 64 channel filter bank using a prototype filter length of 640 coefficients and a system delay of 319 samples is given. The method substantially reduces artifacts due to aliasing emerging from independent modifications of subband signals, for example when using a filter bank as a spectral equalizer. The method is preferably implemented in software, running on a standard PC or a digital signal processor (DSP), but can also be hardcoded on a custom chip. The method offers improvements for various types of digital equalizers, adaptive filters, multiband companders and spectral envelope adjusting filter banks used in high frequency reconstruction (HFR) or parametric stereo systems.

公开(公告)号：US09715881B1

公开(公告)日：2017-07-25

申请号：US15478797

申请日：2017-04-04

Applicant: Dolby International AB

Inventor： Per Ekstrand

IPC: G06F7/00 ,  G10L19/02 ,  H03H17/02 ,  G10L19/008 ,  G10L19/26 ,  G06F17/11

CPC classification number: H04R3/04 ,  G06F17/10 ,  G06F17/11 ,  G10L19/008 ,  G10L19/0204 ,  G10L19/0208 ,  G10L19/26 ,  G10L19/265 ,  G10L21/00 ,  H03H17/0201 ,  H03H17/0248 ,  H03H17/0266 ,  H03H17/0275 ,  H03H17/0294 ,  H03H2017/0297 ,  H04S7/307

Abstract: An apparatus and method are disclosed for filtering and performing high frequency reconstruction of an audio signal. The apparatus includes an analysis filter bank, a phase shifter, a high frequency reconstructor, and a synthesis filter bank. The analysis filterbank receives real-valued time domain input audio samples and generates complex valued subband samples. The phase shifter shifts a phase of the complex-valued subband samples by an arbitrary amount. The high frequency reconstructor modifies at least some of the complex valued subband samples. A phase shifter unshifts a phase of the modified complex-valued subband samples by the arbitrary amount. The synthesis filter bank receives the modified complex valued subband samples and generates time domain output audio samples. The analysis filter bank comprises analysis filters that are complex exponential modulated versions of a prototype filter with an arbitrary phase shift.

公开(公告)号：US09691400B1

公开(公告)日：2017-06-27

申请号：US15446505

申请日：2017-03-01

Applicant: Dolby International AB

Inventor： Lars G. Liljeryd ,  Per Ekstrand ,  Fredrik Henn ,  Kristofer Kjoerling

IPC: G06F17/00 ,  G10L19/02 ,  G10L19/26 ,  G10L19/00

CPC classification number: G10L19/0208 ,  G10L19/0017 ,  G10L19/0204 ,  G10L19/26 ,  G10L19/265 ,  G10L21/038

Abstract: The present invention relates to a new method and apparatus for improvement of High Frequency Reconstruction (HFR) techniques using frequency translation or folding or a combination thereof. The proposed invention is applicable to audio source coding systems, and offers significantly reduced computational complexity. This is accomplished by means of frequency translation or folding in the subband domain, preferably integrated with spectral envelope adjustment in the same domain. The concept of dissonance guard-band filtering is further presented. The proposed invention offers a low-complexity, intermediate quality HFR method useful in speech and natural audio coding applications.

公开(公告)号：US20170085250A1

公开(公告)日：2017-03-23

申请号：US15364384

申请日：2016-11-30

Applicant: Dolby International AB

Inventor： Per Ekstrand

IPC: H03H17/02 ,  G06F17/11 ,  H04R3/04

CPC classification number: H04R3/04 ,  G06F17/10 ,  G06F17/11 ,  G10L19/008 ,  G10L19/0204 ,  G10L19/0208 ,  G10L19/26 ,  G10L19/265 ,  G10L21/00 ,  H03H17/0201 ,  H03H17/0248 ,  H03H17/0266 ,  H03H17/0275 ,  H03H17/0294 ,  H03H2017/0297 ,  H04S7/307

Abstract: An apparatus for generating real-valued output audio samples is disclosed. The apparatus includes a memory that stores complex-valued input subband samples, real-valued demodulated samples, and the real-valued output audio samples. The apparatus also incudes a phase shifter that shifts a phase of the complex-valued input subband samples by an amount equal to a previously added phase shift and a complex-valued synthesis filter bank that generates the real-valued output audio samples in response to the complex-valued input subband samples, the real-valued demodulated samples, and prototype filter coefficients.

公开(公告)号：US20170070211A1

公开(公告)日：2017-03-09

申请号：US15353914

申请日：2016-11-17

Applicant: Dolby International AB

Inventor： Per Ekstrand

IPC: H03H17/02 ,  H04R3/04

CPC classification number: H04R3/04 ,  G06F17/10 ,  G06F17/11 ,  G10L19/008 ,  G10L19/0204 ,  G10L19/0208 ,  G10L19/26 ,  G10L19/265 ,  G10L21/00 ,  H03H17/0201 ,  H03H17/0248 ,  H03H17/0266 ,  H03H17/0275 ,  H03H17/0294 ,  H03H2017/0297 ,  H04S7/307

Abstract: The document relates to modulated sub-sampled digital filter banks, as well as to methods and systems for the design of such filter banks. In particular, the present document proposes a method and apparatus for the improvement of low delay modulated digital filter banks. The method employs modulation of an asymmetric low-pass prototype filter and a new method for optimizing the coefficients of this filter. Further, a specific design for a 64 channel filter bank using a prototype filter length of 640 coefficients and a system delay of 319 samples is given. The method substantially reduces artifacts due to aliasing emerging from independent modifications of subband signals, for example when using a filter bank as a spectral equalizer. The method is preferably implemented in software, running on a standard PC or a digital signal processor (DSP), but can also be hardcoded on a custom chip. The method offers improvements for various types of digital equalizers, adaptive filters, multiband companders and spectral envelope adjusting filter banks used in high frequency reconstruction (HFR) or parametric stereo systems.

Abstract translation: 该文件涉及调制的次采样数字滤波器组，以及用于设计这种滤波器组的方法和系统。 特别地，本文件提出了一种用于改进低延迟调制数字滤波器组的方法和装置。 该方法采用非对称低通原型滤波器的调制和用于优化滤波器系数的新方法。 此外，给出了使用640系数的原型滤波器长度和319个采样的系统延迟的64信道滤波器组的具体设计。 该方法基本上减少了由于子带信号的独立修改引起的混叠所产生的伪像，例如当使用滤波器组作为频谱均衡器时。 该方法优选地以在标准PC或数字信号处理器（DSP）上运行的软件实现，但也可以在定制芯片上被硬编码。 该方法为各种类型的数字均衡器，自适应滤波器，多频带压缩器和用于高频重建（HFR）或参数立体声系统的频谱包络调整滤波器组提供了改进。

公开(公告)号：US09407993B2

公开(公告)日：2016-08-02

申请号：US14433983

申请日：2013-09-27

Applicant: DOLBY INTERNATIONAL AB

Inventor： Per Ekstrand

IPC: H04R3/04 ,  G10H1/16 ,  G10H1/20 ,  G10L21/038 ,  H04R1/22

CPC classification number: H04R3/04 ,  G10H1/16 ,  G10H1/20 ,  G10H2210/245 ,  G10H2250/235 ,  G10L21/038 ,  H04R1/22 ,  H04R2430/03

Abstract: A latency reduction system in a virtual bass processing system performs harmonic transposition on low frequency components of an audio signal to generate transposed data indicative of harmonics of the audio signal. The system uses a base transposition factor greater than two, and generates the harmonics in response to frequency-domain values determined by forward and inverse transform stages that use asymmetric analysis and synthesis windows. The system combines a virtual bass signal with the delayed wide band audio signal through analysis filter banks having filter coefficient truncated Nyquist filters. The virtual bass signal may lag the delayed wide band audio signal when combining with the audio signal to further reduce the latency caused by the harmonic transposition. The virtual bass input signal may be directly routed from a CQMF analysis filter bank of a preceding Hybrid filter bank stage, in order to avoid the delay associated with a Nyquist filter bank.

Abstract translation: 虚拟低音处理系统中的延迟降低系统在音频信号的低频分量上执行谐波转置，以产生表示音频信号的谐波的转置数据。 系统使用大于2的基本转置因子，并响应于使用不对称分析和综合窗口的正向和反向变换阶段确定的频域值产生谐波。 该系统通过具有滤波器系数截短的奈奎斯特滤波器的分析滤波器组将虚拟低音信号与延迟的宽带音频信号组合。 当与音频信号组合时，虚拟低音信号可能延迟延迟的宽带音频信号，以进一步减少由谐波转置引起的等待时间。 虚拟低音输入信号可以从先前的混合滤波器组级的CQMF分析滤波器组直接路由，以避免与奈奎斯特滤波器组相关联的延迟。

公开(公告)号：US09190067B2

公开(公告)日：2015-11-17

申请号：US14614172

申请日：2015-02-04

Applicant: Dolby International AB

Inventor： Per Ekstrand ,  Lars Villemoes ,  Per Hedelin

IPC: G10L19/14 ,  G10L19/26 ,  G10L21/038

CPC classification number: G10H1/0091 ,  G10H1/125 ,  G10H2210/311 ,  G10L19/265 ,  G10L21/038 ,  G10L21/0388

Abstract: The present document relates to audio coding systems which make use of a harmonic transposition method for high frequency reconstruction (HFR), and to digital effect processors, e.g. so-called exciters, where generation of harmonic distortion adds brightness to the processed signal. In particular, a system configured to generate a high frequency component of a signal from a low frequency component of the signal is described. The system may comprise an analysis filter bank (501) configured to provide a set of analysis subband signals from the low frequency component of the signal; wherein the set of analysis subband signals comprises at least two analysis subband signals; wherein the analysis filter bank (501) has a frequency resolution of Δf. The system further comprises a nonlinear processing unit (502) configured to determine a set of synthesis subband signals from the set of analysis subband signals using a transposition order P; wherein the set of synthesis subband signals comprises a portion of the set of analysis subband signals phase shifted by an amount derived from the transposition order P; and a synthesis filter bank (504) configured to generate the high frequency component of the signal from the set of synthesis subband signals; wherein the synthesis filter bank (504) has a frequency resolution of FΔf ; with F being a resolution factor, with F≧1; wherein the transposition order P is different from the resolution factor F.

Abstract translation: 本文件涉及利用用于高频重构（HFR）的谐波转置方法的音频编码系统以及数字效果处理器，例如， 所谓的兴奋剂，其中谐波失真的产生增加处理信号的亮度。 特别地，描述了被配置为从信号的低频分量产生信号的高频分量的系统。 该系统可以包括分析滤波器组（501），其被配置为从信号的低频分量提供一组分析子带信号; 其中所述一组分析子带信号包括至少两个分析子带信号; 其中所述分析滤波器组（501）的频率分辨率为＆Dgr; f。 该系统还包括非线性处理单元（502），其被配置为使用转置顺序P从所述一组分析子带信号中确定一组合成子带信号; 其中所述合成子带信号集合包括所述一组分析子带信号的一部分，所述分析子带信号的相位偏移量是从所述置换顺序P导出的量; 以及合成滤波器组（504），被配置为从所述合成子带信号的集合生成所述信号的高频分量; 其中所述合成滤波器组（504）具有F＆Dgr; f的频率分辨率; F为分辨率因子，F≥1; 其中转置次数P与分辨率因子F不同

公开(公告)号：US08971551B2

公开(公告)日：2015-03-03

申请号：US13652023

申请日：2012-10-15

Applicant: Dolby International AB

Inventor： Per Ekstrand

IPC: H03G5/00

CPC classification number: H04R3/04 ,  G10H1/16 ,  G10H1/20 ,  G10H2210/245 ,  G10H2250/235 ,  G10L21/038 ,  H04R1/22 ,  H04R2430/03

Abstract: In some embodiments, a virtual bass generation method including steps of: performing harmonic transposition on low frequency components of an input audio signal (typically, bass frequency components expected to be inaudible during playback of the input audio signal using an expected speaker or speaker set) to generate transposed data indicative of harmonics (which are expected to be audible during playback, using the expected speaker(s), of an enhanced version of the input audio which includes the harmonics); generating an enhancement signal in response to the transposed data; and generating an enhanced audio signal by combining (e.g., mixing) the enhancement signal with the input audio signal. Other aspects are systems (e.g., programmed processors) and devices (e.g., devices having physically-limited bass reproduction capabilities, such as, for example, a notebook, tablet, mobile phone, or other device with small speakers) configured to perform any embodiment of the method.

Abstract translation: 在一些实施例中，虚拟低音产生方法包括以下步骤：在输入音频信号的低频分量（通常是预期在使用预期扬声器或扬声器组播放输入音频信号的情况下听不到的低音频率分量）执行谐波转置 以产生指示谐波的转置数据（其预期在播放期间使用预期的扬声器可听到包括谐波的输入音频的增强版本）; 响应于所转置的数据产生增强信号; 以及通过将增强信号与输入音频信号组合（例如，混合）来生成增强音频信号。 其他方面是被配置为执行任何实施例的系统（例如，编程处理器）和设备（例如，具有物理限制的低音再现功能的设备，例如笔记本，平板电脑，移动电话或具有小型扬声器的其他设备） 的方法。

公开(公告)号：US20140229188A1

公开(公告)日：2014-08-14

申请号：US14252947

申请日：2014-04-15

Applicant: Dolby International AB

Inventor： Lars G. Liljeryd ,  Kristofer Kjoerling ,  Per Ekstrand ,  Fredrik Henn

IPC: G10L19/06

CPC classification number: G10L19/028 ,  G10L19/035 ,  G10L19/06 ,  G10L19/26 ,  G10L19/265 ,  G10L21/038 ,  G10L25/18

Abstract: The present proposes new methods and an apparatus for enhancement of source coding systems utilising high frequency reconstruction (HFR). It addresses the problem of insufficient noise contents in a reconstructed highband, by Adaptive Noise-floor Addition. It also introduces new methods for enhanced performance by means of limiting unwanted noise, interpolation and smoothing of envelope adjustment amplification factors. The present invention is applicable to both speech coding and natural audio coding systems.

Abstract translation: 本发明提出了利用高频重建（HFR）来增强源编码系统的新方法和装置。 它通过自适应噪声层加法解决了重构高频带中噪声含量不足的问题。 它还通过限制不需要的噪声，包络调整放大因子的插值和平滑来介绍新的增强性能的方法。 本发明适用于语音编码和自然音频编码系统。

公开(公告)号：US12260869B2

公开(公告)日：2025-03-25

申请号：US18633112

申请日：2024-04-11

Applicant: DOLBY INTERNATIONAL AB

Inventor： Lars Villemoes ,  Heiko Purnhagen ,  Per Ekstrand

IPC: G10L19/16 ,  G10L19/035 ,  G10L19/24 ,  G10L21/038

Abstract: Embodiments relate to an audio processing unit that includes a buffer, bitstream payload deformatter, and a decoding subsystem. The buffer stores at least one block of an encoded audio bitstream. The block includes a fill element that begins with an identifier followed by fill data. The fill data includes at least one flag identifying whether enhanced spectral band replication (eSBR) processing is to be performed on audio content of the block. A corresponding method for decoding an encoded audio bitstream is also provided.