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EP-4399883-B1 - MULTI-CHANNEL AUDIO PROCESSING METHOD, SYSTEM AND STEREO APPARATUS

EP4399883B1EP 4399883 B1EP4399883 B1EP 4399883B1EP-4399883-B1

Inventors

  • LI, XIAOCHENG
  • ZHENG, Jianwen
  • SHIH, Shaofu

Dates

Publication Date
20260506
Application Date
20210910

Claims (11)

  1. A multi-channel audio processing method, comprising: receiving multi-channel audio signals from an external audio source, the multi-channel audio signals comprises a pair of surround channel signals and a pair of top channel signals; applying a crosstalk cancellation process in consideration of a head-related transfer function to the pair of top channel signals, to produce a pair of processed top channel signals, the head-related transfer function is configured to provide an elevation angle; mixing the pair of processed top channel signals, respectively, with the pair of surround channel signals, to produce a pair of mixed surround channel signals; providing the pair of mixed surround channel signals, respectively, to a pair of surround speakers.
  2. The multi-channel audio processing method according to claim 1, wherein the head-related transfer function is configured to provide an elevation angle of 30-60 degrees.
  3. The multi-channel audio processing method according to claim 1, wherein the crosstalk cancellation process in consideration of the head-related transfer function may be defined as one of the followings: H = C HRTF C H C − 1 C H ; H = C H C − 1 C H C HRTF ; H = C H C − 1 C HRTF C H , wherein H stands for the crosstalk cancellation process in consideration of the head-related transfer function, C HRTF stands for the head-related transfer function, C stands for a transfer function between speaker(s) and a listener, the superscript H stands for a conjugate transpose operation, and the superscript -1 stands for an inverse operation.
  4. The multi-channel audio processing method according to claim 1, further comprising: calibrating the crosstalk cancellation process by adjusting parameters of the crosstalk cancellation process, wherein the parameters comprises a distance and an angle of an intended listener position relative to the pair of the surround speakers.
  5. The multi-channel audio processing method according to any of claims 1-4, wherein calibrating the crosstalk cancellation process is performed automatically.
  6. The multi-channel audio processing method according to claim 5, wherein calibrating the crosstalk cancellation process is performed upon an actuation of the user.
  7. The multi-channel audio processing method according to any of claims 1-4, wherein multi-channel audio signals comprises 5.1.4 or 7.1.4 channel audio signals, and the pair of top channel signals is a pair of top rear channel signals.
  8. The multi-channel audio processing method according to any of claims 1-4, further comprising: delaying the pair of surround channel signals to synchronize with the pair of processed top channel signals prior to the mixing.
  9. A multi-channel audio processing system, comprising a processor for performing a method according to any of claims 1-8.
  10. A stereo apparatus, comprising: an audio source; a speaker system comprising a plurality of speakers, wherein the plurality of speaker comprises a pair of surround speakers; and a multi-channel audio processing system according to claim 9, the multi-channel audio processing system being configured to receive multi-channel audio signals from the audio source.
  11. The stereo apparatus according to claim 10, wherein the speaker system is a 5.1.2 speaker system or a 7.1.2 speaker system, wherein the pair of top channel signals is a pair of top rear channel signals, and the speaker system does not comprises a top rear speaker.

Description

TECHNICAL FIELD This present disclosure relates to a method for processing multi-channel audio signals, a system for processing multi-channel audio signals and a stereo apparatus comprising such a system. BACKGROUND With the development of multi-channel surround sound technologies like Dolby Atmos and DTS: X, multi-channel speaker systems are becoming increasingly popular for consumers. These technologies have their own multi-channel audio encoding techniques that provide multi-channel audio signals, each of which is intended to be provided to and played back by a respective speaker of the multi-channel speaker systems, to provide a good spatial audio resolution as well as a good immersive surround sound experience. Multi-channel speaker systems are normally named after their speakers or audio channels, such as 5.1/7.1/9.1/5.1.2/7.1.2/9.1.2/5.1.4/7.1.4/9.1.4 speaker systems. For example, a 5.1.2 speaker system is a multi-channel speaker system, with the "5" referring to left, right, center, left surround and right surround speakers and their five corresponding channels, and the "1" referring to a woofer speaker and its corresponding channel, and the "2" referring to left top and right top speakers and their two corresponding channels. Similarly, a 5.1.4 speaker system is a multi-channel speaker system, with the "5" referring to left, right, center, left surround and right surround speakers and their five corresponding channels, and the "1" referring to a low frequency effect speaker and its corresponding channel, and the "4" referring to left top front, right top front, left top rear and right top rear speakers and their four corresponding channels. With the four top speakers or top channels in the multi-channel speaker system, such as a 5.1.4 or 7.1.4 speaker system, the speaker system can better reproduce height effects and thus provide a better immersive surround sound experience. For example, in some movie scenarios, such as those having a helicopter flying therearound, the 5.1.4 or 7.1.4 speaker system will be able to achieve the full 360-degree surround experience, namely the helicopter completes the full circle with pinpoint accuracy. On the other hand, with 5.1.2 or 7.1.2 speaker systems, due to the lack of the top rear speaker pair, the speaker system can only complete the front 180-degree surround sound. As a result, the helicopter only flies left and right in front of the listener, rather than flies a full circle around the listener as in the 5.1.4/7.1.4 channel speaker systems. Similarly, speaker systems without top speakers such as 5.1/7.1 channel speaker systems may downmix the top channels to the front and surround channels, and thus may not produce the height effects and may deteriorate the surround sound experience. Therefore, there is a need to achieve a height effect, such as a 360-degree surround height effect, to provide a better surround sound experience, by using a speaker system that does not have a full four top speakers. There have been attempts to achieve a better spatial audio by means of virtual sound features. Those features are commonly used to compensate for the missing speakers for the 2D listening positions to enhance the surround sound experience. The virtual sound features are achieved by algorithms based on the crosstalk cancellation, which relies on phase alignment at a cost of reduced sweet spot. Namely, when the listener is away from the sweet spot, the virtual effect degrades significantly. In some cases, this will further lead to phase misalignment which results in a deteriorated sound experience and spatial accuracy. "Virtual Height Speaker Rendering for Samsung 10.2-Channel Vertical Surround System",AES Convention 131; October 2011, AES, by Lee Young Woo et al., discloses rendering 10.2-channel audio comprising three top channels on a 7.1-channel speaker layout using virtual height speaker rendering. The top channels are rendered on the 7.1-channel speaker layout using a spectral filter based on HRTF spectrum. The processed top channels are mixed to some of the channels of the 7.1-channel speaker layout, comprising surround channels. Some of the mixtures are rendered on the surround speakers. Therefore, there is a need for a better spatial audio by means of virtual sound features, with improved sound effect even when the listener is away from the sweet spot. SUMMARY OF THE INVENTION According to one aspect of the disclosure, a multi-channel audio processing method is provided. The multi-channel audio processing method comprises: receiving multi-channel audio signals from an external audio source, the multi-channel audio signals comprises a pair of surround channel signals and a pair of top channel signals; applying a crosstalk cancellation process in consideration of a head-related transfer function to the pair of top channel signals, so as to produce a pair of processed top channel signals, the head-related transfer function is configured to provide an elevation