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US 7,072,726 B2Granted
Converting M channels of digital audio data into N channels of digital audio data
AssigneeMicrosoft Corporation
InventorsMei L. Wilson, Shafiq ur Rahman, Rebecca C. Weiss, Brian Crites, Sohail Baig Mohammed, Michael A. Wall
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Abstract
Audio data having M channels includes a header with metadata specifying a conversion function for converting the M channels of digital audio data into N channels of data. The metadata is a string of coefficients, which may be specified by the content author, to define to conversion of the M channels of digital audio data into N channels.
Claims12
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 (Y1–YM channels) to an X audio data set having N channels (X1–XN channels);
- wherein the coefficients comprise coefficients KAj 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).
45 more elements
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 (Y1–YM channels) to an X audio data set having N channels (X1–XN channels)
- wherein the coefficients comprise coefficients KAj 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 LYEMIX and wherein the fold-down function comprises:
- L(N)=B*[R(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 the fold-down function is based on the following mix table wherein;
- L(M)
- R(M)
- C(M)
- LFE(M)
- LS(M)
- RS(M)
- L(N)
- W
- −INFINITY
- Y
- Z
- X
- −INFINITY
- R(N)
- −INFI-
- W
- Y
- Z
- −INFI-
- X
- NITY
- NITY
- wherein:
- W=20*65536*log10 (B);
- X=20*65536*log10 (SMIX*B);
- Y=20*65536*log10 (CMIX*B);
- Z=20*65536*log10 (LFEMIX*B);
- and
- −INFINITY represents negative infinity.
74 more elements
Dependencies are inferred from the claim text.