Discrete multichannel audio with a backward compatible mix

Abstract

A multichannel audio format provides a truly discrete as well as a backward compatible mix for surround-sound, front or other discrete audio channels in cinema, home theater, or music environments. The additional discrete audio signals are mixed with the existing discrete audio channels into a predetermined format such as the 5.1 audio format. In addition these additional discrete audio channels are encoded and appended to the predetermined format as extension bits in the bitstream. The existing base of multichannel decoders can be used in combination with a mix decoder to reproduce truly discrete N.1 multichannel audio.

1 . A medium recorded with M discrete audio channels that carry N mixed audio signals, and at least one discrete extension channel that carries at least one of the N audio signals.  
   
   
       2 . The medium of  claim 1 , wherein the M discrete audio channels are recorded on the medium in a predetermined multichannel audio format and the discrete extension channel is recorded on the medium as extension bits appended to said predetermined multichannel audio format.  
   
   
       3 . The medium of  claim 2 , wherein the medium is compatible for playback on an existing base of audio decoders configured to read media recorded with the predetermined multichannel audio format and on audio coders configured to read media recorded with the predetermined multichannel audio format and the discrete extension channel.  
   
   
       4 . The medium of  claim 2 , wherein the M discrete audio channels and at least one discrete extension channel are recorded on the medium as a sequence of audio frames that form a digital bitstream, each said audio frame including a sync word, audio data in a predetermined multichannel audio format representative of said discrete audio channels, and audio data appended to said multichannel audio format representative of said discrete extension channel.  
   
   
       5 . The medium of  claim 4 , wherein the size of the audio frame may vary from frame-to-frame to accommodate the discrete extension channels.  
   
   
       6 . The medium of  claim 1 , wherein M equals N.  
   
   
       7 . The medium of  claim 1 , wherein N is greater than M.  
   
   
       8 . The medium of  claim 7 , wherein the medium is recorded with N minus M discrete extension channels each carrying a different one of the N audio signals.  
   
   
       9 . The medium of  claim 8 , wherein the M equal two discrete audio channels are surround-sound channels, the medium being further recorded with three discrete front channels that carry respective discrete front audio signals and a sub channel that carriers a subwoofer signal, said three front channels, two surround-sound channels and sub channel being recorded on the medium in a 5.1 audio format and said discrete extension surround-sound channel being recorded as extension bits appended to said 5.1 audio format.  
   
   
       10 . The medium of  claim 8 , wherein the medium is recorded with N minus two discrete extension channels each carrying a different one of the N audio signals.  
   
   
       11 . The medium of  claim 9 , wherein the N audio signals comprise a left surround signal, a right surround signal and center surround signal.  
   
   
       12 . The medium of  claim 1 , wherein the N audio signals comprise surround-sound audio signals.  
   
   
       13 . The medium of  claim 1 , wherein said discrete audio channels are carried on said medium in a digital format.  
   
   
       14 . The medium of  claim 13 , wherein said medium is film having optically recorded symbols representing digital information, the digital information, in turn, representing said discrete audio channels.  
   
   
       15 . The medium of  claim 13 , wherein said medium is an optical disc having pits impressed in the disc surface representing digital information, the digital information, in turn, representing said discrete audio channels.  
   
   
       16 . The medium of  claim 15 , wherein said medium is a digital video disc (DVD).  
   
   
       17 . The medium of  claim 1 , wherein the media is recorded with N discrete extension channels of which N minus M channels carry discrete audio signals and the remaining M channels carry difference audio signals.  
   
   
       18 . The medium of  claim 17 , wherein the M difference audio signals represent a weighted difference between an M channel audio mix and the corresponding M channels in an N channel audio mix.  
   
   
       19 . An article of manufacture, comprising: 
 a portable machine readable storage medium; and    a digital bitstream representing a multichannel audio signal including N audio signals that are mixed onto M discrete audio channels where N>M with at least one of said N audio signals being carried on at least one discrete extension channel, said discrete audio channels and discrete extension channel being recorded onto said portable machine readable storage medium as a sequence of audio frames, each said audio frame comprising: 
 audio data in a predetermined multichannel audio format representative of said discrete audio channels, and  
 audio data appended to said multichannel audio format representative of said discrete extension channel.  
   
   
   
       20 . The medium of  claim 19 , wherein the size of the audio frame may vary from frame-to-frame to accommodate the discrete extension channels.  
   
   
       21 . The medium of  claim 19 , wherein said discrete audio channels are carried on said medium in a digital format, said medium is an optical disc having pits impressed in the disc surface representing digital information, the digital information, in turn, representing said discrete audio channels.  
   
   
       22 . A multichannel audio signal encoded with M discrete audio channels that carry N mixed audio signals and a discrete extension surround-sound channel that carries one of the audio signals.  
   
   
       23 . The signal of  claim 22 , wherein the M discrete audio channels are encoded in a predetermined multichannel audio format and the discrete extension channel is encoded and appended to said predetermined multichannel audio format.  
   
   
       24 . The signal of  claim 23 , wherein the signal is encoded with N minus M discrete extension channels each carrying a different one of the N audio signals.  
   
   
       25 . The signal of  claim 22 , wherein said signal comprises a carrier signal that is encoded with the M discrete audio channels and the discrete extension channel.  
   
   
       26 . The medium of  claim 25 , wherein the signal is encoded with N discrete extension channels of which N minus M channels carry discrete audio signals and the remaining M channels carry difference audio signals.  
   
   
       27 . The medium of  claim 26 , wherein the M difference audio signals represent a weighted difference between an M channel audio mix and the corresponding M channels in an N channel audio mix.  
   
   
       28 . A method of recording multichannel audio on a media with an extended multichannnel audio format for reproduction by either an existing base of audio decoders configured to read media recorded with a predetermined multichannel audio format or a base of audio decoders configured to read media recorded with the extended multichannnel audio format, comprising: 
 mixing sound information for N audio signals;    mixing the N audio signals into M audio signals where M is less than N;    recording said M audio signal in M discrete audio channels with the predetermined multichannel audio format onto the media; and    recording at least one of the audio signals in respective discrete extension audio channels as extension bits appended to the predetermined multichannel audio format on the media, which together comprise the extended multichannnel audio format.    
   
   
       29 . The method of  claim 28 , wherein said discrete audio channels and discrete extension channel are recorded onto said media as a sequence of audio frames, further comprising varying the size of the audio frame from frame-to-frame to accommodate the discrete extension channels.  
   
   
       30 . The method of  claim 28 , where N minus M of the audio signals are recorded in respective discrete extensions audio channels.  
   
   
       31 . The method of  claim 28 , wherein said audio signals comprise left, right and center surround-sound signals, sound information for three front and a sub audio signal being mixed and recorded with the two discrete surround-sound channels in a 5.1 channel audio format.  
   
   
       32 . The method of  claim 28 , wherein the N and M audio signals represent N-channel and M-channel mixes, respectively, further comprising: 
 computing weighted difference signals between the M-channel mix and the corresponding M discrete audio signals in the N-channel mix, and    recording the weighted difference signals on respective discrete extension channels.    
   
   
       33 . A method of reproducing multichannel audio, comprising: 
 receiving a media having a recorded bitstream, said bitstream including M discrete audio channels that carry N mixed audio signals where N>M in a predetermined multichannel audio format and at least one discrete extension channel, each one carrying one of the N audio signals as extension bits appended to said predetermined multichannel audio format;    reading out the bits in the predetermined multichannel audio format while ignoring the extension bits;    decoding the bits in the predetermined multichannel audio format to reproduce said M discrete audio channels;    applying the M discrete audio channels to respective discrete speaker channels to reproduce M discrete audio signals and at least one phantom audio signal.    
   
   
       34 . The method of  claim 33 , wherein said M discrete audio channels are left and right surround-sound channels and said N discrete audio signals comprise left, right and center surround-sound signals, said discrete extension channel carrying said center surround-sound signal, which although ignored during read out, is reproduced as a phantom center surround signal.  
   
   
       35 . The method of  claim 33 , wherein said discrete audio channels and discrete extension channel are recorded onto said media as a sequence of audio frames that are read out a frame at a time, the size of the audio frame recorded on said media being varied from frame-to-frame to accommodate the discrete extension channels.  
   
   
       36 . A method of reproducing multichannel audio, comprising: 
 receiving a media having a recorded bitstream, said bitstream including M discrete audio channels that carry N mixed audio signals where N>M in a predetermined multichannel audio format and at least one discrete extension channel, each one carrying one of the N audio signals as extension bits appended to said predetermined multichannel audio format;    reading out the bits in the predetermined multichannel audio format while ignoring the extension bits; decoding the bits in the predetermined multichannel audio format to reproduce said M discrete audio channels;    matrix decoding the M audio channels to provide N discrete audio channels that carry matrix decoded audio representations of the N mixed audio signals; and applying the N discrete audio channels to respective discrete speakers channels to reproduce matrix decoded multichannel audio.    
   
   
       37 . The method of  claim 36 , wherein said M discrete audio channels are left and right surround-sound channels and said N discrete audio signals comprise left, right and center surround-sound signals, said discrete extension channel carrying said center surround-sound signal, which because it is ignored during read out, is reproduced as matrix decoded audio.  
   
   
       38 . The method of  claim 36 , wherein said discrete audio channels and discrete extension channel are recorded onto said media as a sequence of audio frames that are read out a frame at a time, the size of the audio frame recorded on said media being varied from frame-to-frame to accommodate the discrete extension channels.