Patent ID: 8868433

Claim:
A method of operating an audio decoder to decode audio data that includes encoded blocks of N.n channels of audio data to form decoded audio data that includes M.m channels of decoded audio, M>1, n being the number of low frequency effects channels in the encoded audio data, and m being the number of low frequency effects channels in the decoded audio data, the method comprising: accepting the audio data that includes blocks of N.n channels of encoded audio data encoded by an encoding method, the encoding method including transforming N.n channels of digital audio data, and forming and packing frequency domain exponent and mantissa data; and decoding the accepted audio data, the decoding including: unpacking and decoding the frequency domain exponent and mantissa data; determining transform coefficients from the unpacked and decoded frequency domain exponent and mantissa data; inverse transforming the frequency domain data and applying further processing to determine sampled audio data; and time-domain downmixing at least some blocks of the determined sampled audio data according to downmixing data for the case M<N, wherein the method includes identifying one or more non-contributing channels of the N.n input channels, a non-contributing channel being a channel that does not contribute to the M.m channels, and wherein the method does not carry out inverse transforming the frequency domain data and the applying further processing on the one or more identified non-contributing channels.