Patent ID: 7072726

Claim:
A computer readable medium having computer executable instructions stored thereon, the medium comprising: audio data having M channels and including a header wherein the header includes metadata specifying a conversion function for converting the M channels of the audio data into N channels of data; wherein the conversion function is a fold-down function specified by the metadata which includes a plurality of coefficients which define a conversion of a Y audio data set having M channels (Y 1 –Y M channels) to an X audio data set having N channels (X 1 –X N channels); wherein the coefficients comprise coefficients K Aj which define the fold-down as follows: X A = ∑ j = 1 M ⁢ K Aj ⁢ Y j ( for ⁢ ⁢ A = 1 ⁢ ⁢ to ⁢ ⁢ N ) ; wherein the audio data comprises a 5.1 audio stream having six channels having left front, right front, center, low frequency, left surround and right surround channels such that M=6, wherein the destination device comprises a stereo destination device having left and right channels such that N=2, wherein the coefficients include B, SMIX, CMIX and LFEMIX and wherein the fold-down function comprises: L ( N )= B*[L ( M )+ SMIX*LS ( M )+ CMIX*C ( M )+ LFEMIX*LFE ( M )] and R ( N )= B*[R ( M )+ SMIX*RS ( M )+ CMIX*C ( M )+ LFEMIX*LFE ( M )] wherein: L(N) is the data for the left channel of the stereo destination device; L(M) is the left front channel data of the 5.1 audio stream; LS(M) is the left surround channel data of the 5.1 audio stream; C(M) is the center channel data of the 5.1 audio stream; LFE(M) is the low frequency channel data of the 5.1 audio stream; R(N) is the data for the right channel of the stereo destination device; R(M) is the right front channel data of the 5.1 audio stream; and RS(M) is the right surround channel data of the 5.1 audio stream; and wherein B=1/(1+SMIX+CMIX+LFEMIX).