Patent ID: 11869517
Assignee: HUAWEI TECHNOLOGIES CO., LTD.
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 4:
5. A downmixed signal calculation apparatus comprising:
a memory for storing computer-executable instructions; and
at least one processor operatively coupled to the memory, the at least one processor being configured to execute the computer-executable instructions to:
determine that a first condition or a second condition is true, wherein determine that the first condition is true comprises determine that a previous frame of a current frame of a stereo audio signal is not a switching frame based on a switching flag of the previous frame and determining that a residual signal in the previous frame does not need to be encoded based on a coding flag of the previous frame, and determine that the second condition is true comprises determine that the current frame is not a switching frame based on a switching flag of the current frame and a residual signal in the current frame does not need to be encoded based on a coding flag of the current frame;
in response to the determining that one of the first condition or the second condition is true, calculate a first downmixed signal in the current frame, wherein the at least one processor is configured to execute the computer-executable instructions to:
obtain a second downmixed signal in the current frame;
obtain a downmix compensation factor of the current frame, wherein the obtaining the downmix compensation factor of the current frame comprises:
calculating a downmix compensation factor in a subframe i of the current frame based on a first flag, wherein the first flag indicates whether a stereo parameter other than an inter-channel time difference parameter needs to be encoded in the current frame, the current frame comprises P subframes, and the downmix compensation factor of the current frame comprises the downmix compensation factor of the subframe i of the current frame, wherein both P and i are integers, P≥2, and i∈[0, P−1]; wherein a second frequency-domain signal in the subframe i of the current frame is a left channel frequency-domain signal in the subframe i of the current frame, and the calculating the downmix compensation factor of the subframe i of the current frame comprises:

calculating the downmix compensation factor of the subframe i of the current frame based on the left channel frequency-domain signal in the subframe i of the current frame and a right channel frequency-domain signal in the subframe i of the current frame, wherein
a downmix compensation factor αi(b) in a subband b in the subframe i of the current frame is calculated according to the following formula:

αi(b)=√{square root over (E_Li(b))}+√{square root over (E_Ri(b))}−√{square root over (E_LRi(b))}/2 √{square root over (E_Li(b))}

E_Li(b)=Σk=band_limits(b)k=band_limits(b+1)−1Lib″(k)2,

E_Ri(b)=Σk=band_limits(b)k=band_limits(b+1)−1Rib″(k)2, and

E_LRi(b)=Σk=band_limits(b)k=band_limits(b+1)−1[Lib″(k)2+Rib″(k)]2; or

E_Li(b)=Σk=band_limits(b)k=band_limits(b+1)−1Lib′(k)2,

E_Ri(b)=Σk=band_limits(b)k=band_limits(b+1)−1Rib′(k)2, and

E_LRi(b)=Σk=band_limits(b)k=band_limits(b+1)−1[Lib′(k)+Rib′(k)]2; wherein

E_Li(b) represents an energy sum of a left channel frequency-domain signal in the subband b in the subframe i of the current frame; E_Ri(b) represents an enemy sum of a right channel frequency-domain sural in the subband b in the subframe i of the current frame; E_LRi(b) represents an energy sum of the energy of the left channel frequency-domain signal and the energy of the right channel frequency-domain signal in the subband b in the subframe i of the current frame; band_limits(b) represents a minimum frequency bin index value of the subband b in the subframe i of the current frame; band_limits(b+1) represents a minimum frequency bin index value of a subband b+1 in the subframe i of the current frame; Lib″(k) represents a left channel frequency-domain signal that is in the subband b in the subframe i of the current frame and that is obtained after adjustment based on a stereo parameter: Rib″(k) represents a right channel frequency-domain signal that is in the subband b in the subframe i of the current frame and that is obtained after adjustment based on the stereo parameter; Lib′(k) represents a left channel frequency-domain signal that is in the subband b in the subframe i of the current frame and that is obtained after time-shift adjustment; Rib′(k) represents a right channel frequency-domain signal that is in the subband b in the subframe i of the current frame and that is obtained after time-shift adjustment; and k represents a frequency bin index value, wherein each subframe of the current frame comprises M subbands, the downmix compensation factor of the subframe i of the current frame comprises the downmix compensation factor of the subband b in the subframe i of the current frame, b is an integer, b ∈[0, M−1], and M≥2; and
the calculating a compensated downmixed signal in a subframe i of the current frame comprises:
calculating a compensated downmixed signal in the subband b in the subframe i of the current frame according to the following formula:

DMX_compib(k)=αi(b)*Lib″(k), wherein

DMX_compib(k) represents the compensated downmixed signal in the subband b in the subframe i of the current frame, k represents a frequency bin index value, and k∈[band_limits(b), band_limits(b+1)−1]; and

correct the second downmixed signal in the current frame based on the downmix compensation factor of the current frame, to obtain the first downmixed signal in the current frame; and

determine the first downmixed signal in the current frame as a downmixed signal in a preset frequency band of the current frame.