Method of processing audio for playback of immersive audio
A method ( 200 ) of processing audio in an immersive audio format comprising at least one height audio channel, comprising: obtaining ( 250 ) two height audio signals from at least a portion of the at least one height audio channel: modifying ( 270 ) a relative phase between the two height audio signals in frequency bands in which phase differences are predominantly out of phase to obtain two phase modified height audio signals: and playing back ( 290 ) the processed audio comprising the two phase modified height audio signals with at least two audio loudspeakers. The phase differences occur as a result of having monaural signals emanated from two audio loudspeakers at one or more listening positions symmetrically off-center with respect to the at least two loudspeakers, laterally spaced with respect to each of said one or more listening positions. The method allows perception of sound height/elevation without using overhead speakers.
1 . A method of processing audio in an immersive audio format comprising at least one height audio channel, for playing back the processed audio with a non-immersive loudspeaker system of at least two audio loudspeakers without overhead loudspeakers, in a listening environment including two or more listening positions, wherein each of the two or more listening positions is symmetrically off-center with respect to an elevation plane that is perpendicular to a plane in which the at least two loudspeakers reside, such that each of the two or more listening positions is equidistant from the elevation plane, and each of the at least two loudspeakers is laterally spaced with respect to each of said two or more listening positions such that, when two monaural audio signals are emanated from the at least two loudspeakers, inter-loudspeaker differential phases, IDPs, occur at the two or more listening positions as a result of acoustic characteristics of the listening environment, the method comprising:
obtaining two monoaural height audio signals from at least a portion of the at least one height audio channel;
modifying a relative phase between the two monaural height audio signals in frequency bands in which the IDPs occurring at the two or more listening positions when the two height channels are emanated from the at least two loudspeakers, are out of phase, to obtain two phase modified height audio signals in which the IDPs are in-phase; and
playing back the processed audio at the at least two audio loudspeakers, wherein the processed audio comprises the two phase modified height audio signals and wherein phase modification of the two monaural height audio signals causes a perception of sound height when played back by the non-immersive loudspeaker system without overhead loudspeakers.
2 . The method of claim 1 , wherein the audio in the immersive audio format further comprises at least two audio channels and wherein the method further comprises mixing each of the two phase modified height audio signals with one of the two audio channels.
3 . The method of claim 1 , wherein the audio in the immersive audio format further comprises a center channel and wherein the method further comprises mixing each of the two phase modified height audio signals with the center channel.
4 . The method of claim 1 , wherein the audio in the immersive audio format has a single height audio channel, and wherein obtaining the two monaural height audio signals comprises obtaining the two monaural height audio signals both corresponding to the single height audio channel.
5 . The method of claim 1 , wherein the audio in the immersive audio format comprises at least two height audio channels, and wherein obtaining the two monaural height audio signals comprises obtaining the two monaural height audio signals from the at least two height audio channels.
6 . The method of claim 5 , further comprising applying mid/side processing to the at least two height audio channels to obtain a mid signal and a side signal, wherein each of the two height audio signals corresponds to the mid signal.
7 . The method of claim 6 , further comprising mixing the side signal and a signal corresponding to the side signal but with opposite phase of the side signal, with the phase modified height audio signals.
8 . The method of claim 1 , wherein modifying a relative phase between the two height audio signals comprises measuring said IDPs at the one or more of the listening positions.
9 . The method of claim 1 , wherein modifying a relative phase between the two height audio signals is based on a predetermined absolute distances between the one or more listening positions and each of the at least two loudspeakers.
10 . The method of claim 1 , wherein the step of modifying a relative phase between the two height audio signal is triggered upon detection of a movement of a listener at the one or more listening positions.
11 . The method of claim 1 , wherein the listening environment is the interior of a vehicle.
12 . The method of claim 1 , wherein the non-immersive loudspeaker system is a stereo or surround loudspeaker system.
13 . The method of claim 1 , wherein the audio in the immersive audio format is audio rendered in the immersive audio format and/or wherein the immersive audio format is Dolby Atmos, or any X.Y.Z audio format where X≥2 is the number of front or surround audio channels, Y≥0 is, when present, a Low Frequency Effects or subwoofer audio channel, and Z≥1 is the at least one height audio channel.
14 . The method according to claim 1 , wherein said modifying adds a 180 degree phase shift to the relative phase between the two height audio signals for each frequency band in which the IDPs are out of phase.
15 . The method according to claim 14 , wherein the phase of one of the two height audio signals is shifted by +90 degrees and the phase of the other one of the two height audio signals is shifted by −90 degrees.
16 . The method of claim 1 , wherein the phase modification of the two monaural height audio signals causes the two monaural height audio signals to be virtually centered.
17 . An apparatus comprising:
a processor; and
a memory coupled to the processor, wherein the memory stores instructions that, when executed by the processor, cause the processor to process audio in an immersive audio format comprising at least one height audio channel, for playing back the processed audio with a non-immersive loudspeaker system of at least two audio loudspeakers without overhead loudspeakers, in a listening environment including two or more listening positions, wherein each of the two or more listening positions is symmetrically off-center with respect to an elevation plane that is perpendicular to a plane in the at least two loudspeakers reside, such that each of the two or more listening positions is equidistant from the elevation plane, and each of the at least two loudspeakers is laterally spaced with respect to each of said two or more listening positions such that, when two monaural audio signals are emanated from the at least two loudspeakers, inter-loudspeaker differential phases, IDPs, occur at the two or more listening positions as a result of acoustic characteristics of the listening environment, wherein processing the audio comprises:
obtaining two monoaural height audio signals from at least a portion of the at least one height audio channel;
modifying a relative phase between the two monaural height audio signals in frequency bands in which the IDPs occurring at the two or more listening positions when the two height channels are emanated from the at least two loudspeakers, are out of phase, to obtain two phase modified height audio signals in which the IDPs are in-phase; and
providing the processed audio for playback at the at least two audio loudspeakers, wherein the processed audio comprises the two phase modified height audio signals and wherein phase modification of the two monaural height audio signals causes a perception of sound height when played back by the non-immersive loudspeaker system without overhead loudspeakers.
18 . A vehicle comprising the apparatus of claim 17 .
19 . A computer-readable and non-transitory storage medium storing instructions that, when executed by a processor, cause the processor to process audio in an immersive audio format comprising at least one height audio channel, for playing back the processed audio with a non-immersive loudspeaker system of at least two audio loudspeakers without overhead loudspeakers, in a listening environment including two or more listening positions, wherein each of the two or more listening positions is symmetrically off-center with respect to an elevation plane that is perpendicular to a plane in the at least two loudspeakers reside, such that each of the two or more listening positions is equidistant from the elevation plane, and each of the at least two loudspeakers is laterally spaced with respect to each of said two or more listening positions such that, when two monaural audio signals are emanated from the at least two loudspeakers, inter-loudspeaker differential phases, IDPs, occur at the two or more listening positions as a result of acoustic characteristics of the listening environment, wherein processing the audio comprises:
obtaining two monoaural height audio signals from at least a portion of the at least one height audio channel;
modifying a relative phase between the two monaural height audio signals in frequency bands in which the IDPs occurring at the two or more listening positions when the two height channels are emanated from the at least two loudspeakers, are out of phase, to obtain two phase modified height audio signals in which the IDPs are in-phase; and
providing the processed audio for playback at the at least two audio loudspeakers, wherein the processed audio comprises the two phase modified height audio signals and wherein phase modification of the two monaural height audio signals causes a perception of sound height when played back by the non-immersive loudspeaker system without overhead loudspeakers.