US5278909A
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US
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System and method for stereo digital audio compression with co-channel steering
Assignee: International Business Machines Corp
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Filing: 1992-06-08
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Granted: 1994-01-11
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Expires: 2012-06-08
Abstract
Abstract Left right and surround components of a stereo signal are coded into a monaural and small co-channel providing volume steering for recreating a stereo effect with a substantially reduced bit rate. The signal is split into a sum and difference signal, the difference signal is randomized and the sum is added to the randomized difference to comprise the single audio channel. A functional relationship is solved for left and right volumes which is then transmitted for intervals on the co-channel. Decoding of the single transmission channel directs it to left, right, or surround channels based on decoding on the logic co-channel. The co-channel updates left and right volume levels which are interpolated through time to effect smooth volume change. Surround gain is determined from left and right channel gains to maintain unity total volume, with the sum of the squares of the three volume controls being unity.
Inventors
- 👤 Albert D. Edgar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 01:40
CPC Classifications
H; H04; H04H; H04H20/00; H04H20/86; H04H20/88; H04S; H04S1/00; H04S1/007
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
120 words
A method for encoding multiple channels of audio information comprising generating at least one encoded channel numbering less than said multiple channels from said multiple channels; and generating a co-channel of volume steering information for each of said multiple channels from said multiple channels comprised of at least one first co-channel and at least one second co-channel; wherein each of said multiple channels comprises at least one first channel and at least one second channel; wherein the ratio of said first and second co-channels varies in relation to the ratio of the magnitude of said first and second channels; and said magnitude of said first and second co-channels varies in relation to the correlation of said first and second channels.
Claim 2
Independent Claim
120 words
A method for encoding multiple channels of audio information comprising generating at least one encoded channel numbering less than said multiple channels from said multiple channels; and generating a co-channel of volume steering information for each of said multiple channels from said multiple channels comprised of at least one first co-channel and at least one second co-channel; wherein each of said multiple channels comprises at least one first channel and at least one second channel; wherein the ratio of said first and second co-channels varies in relation to the ratio of the magnitude of said first and second channels; and said magnitude of said first and second co-channels varies in relation to the correlation of said first and second channels.
Claim 3
Dependent Claim
26 words
The method of claim 1 wherein the number of said multiple channels is four and the number of said at least one encoded channels is two.
Claim 4
Dependent Claim
26 words
The method of claim 1 wherein the number of said multiple channels is two and the number of said at least one encoded channels is one.
Claim 5
Dependent Claim
62 words
The method of claim 3 wherein said two multiple channels comprise a first and a second channel of audio information; and said at least one encoded co-channel is a function of magnitude of said first channel of audio information; magnitude of said second channel of audio information; and magnitude of a correlation between said first and said second channels of audio information.
Claim 6
Dependent Claim
22 words
The method of claim 4 wherein the frequency of said first and second channels of audio information is limited to preselected ranges.
Claim 7
Dependent Claim
33 words
The method of claim 1 further including executing a summing process of said multiple channels and wherein said at least one encoded channel is generated from said summing process of said multiple channels.
Claim 8
Dependent Claim
18 words
The method of claim 1 wherein the phase of said multiple channels is randomized in said summing process.
Claim 9
Dependent Claim
47 words
The method of claim 7 wherein said randomizing of said phase comprises the steps of deriving first and second signals comprising the sum and difference of said multiple channels, respectively; delaying said second signal to produce a third signal; and summing said third with said first signal.
Claim 10
Dependent Claim
16 words
The method of claim 1 wherein frequency of said multiple channels is limited to preselected ranges.
Claim 11
Dependent Claim
23 words
The method of claim 1 wherein said at least one co-channel is derived substantially only from high frequency components of said multiple channels.
Claim 12
Dependent Claim
42 words
The method of claim 1 wherein said at least one co-channel is derived from information in the low frequency component of said multiple channels; and said at least one encoded channel is generated from the high frequency components of said multiple channels.
Claim 13
Dependent Claim
21 words
The method of claim 1 wherein said at least one encoded channel is functionally related to the magnitudes of said co-channel.
Claim 14
Dependent Claim
15 words
The method of claim 10 wherein said high frequency component is above about 1 kilohertz.
Claim 15
Dependent Claim
128 words
Apparatus for encoding multiple channels of audio information comprising means for generating at least one encoded channel numbering less than said multiple channels from said multiple channels; and means for generating a co-channel of volume steering information for each of said multiple channels from said multiple channels comprised of means for generating at least one first co-channel and at least one second co-channel; wherein of each said multiple channels comprises means for at least one first channel and at least one second channel; wherein the ratio of said first and second co-channels varies in relation to the ratio of the magnitude of said first and second channels; and said magnitude of said first and second co-channels varies in relation to the correlation of said first and second channels.
Claim 16
Dependent Claim
128 words
Apparatus for encoding multiple channels of audio information comprising means for generating at least one encoded channel numbering less than said multiple channels from said multiple channels; and means for generating a co-channel of volume steering information for each of said multiple channels from said multiple channels comprised of means for generating at least one first co-channel and at least one second co-channel; wherein of each said multiple channels comprises means for at least one first channel and at least one second channel; wherein the ratio of said first and second co-channels varies in relation to the ratio of the magnitude of said first and second channels; and said magnitude of said first and second co-channels varies in relation to the correlation of said first and second channels.
Claim 17
Dependent Claim
26 words
The apparatus of claim 14 wherein the number of said multiple channels is four and the number of said at least one encoded channels is two.
Claim 18
Dependent Claim
26 words
The apparatus of claim 14 wherein the number of said multiple channels is two and the number of said at least one encoded channels is one.
Claim 19
Dependent Claim
50 words
The apparatus of claim 16 wherein said two multiple channels comprise a first and a second channel; and said at least one encoded co-channel is a function of magnitude of said first channel; magnitude of said second channel; and magnitude of a correlation between said first and said second channels.
Claim 20
Dependent Claim
19 words
The apparatus of claim 17 wherein the frequency of said first and second channels is limited to preselected ranges.
Claim 21
Dependent Claim
24 words
The apparatus of claim 14 including summing means for generating said at least one channel encoded from a summing process of said multiple channels.
Claim 22
Dependent Claim
20 words
The apparatus of claim 19 including randomizing means for randomizing the phase of said multiple channels in said summing process.
Claim 23
Dependent Claim
58 words
The apparatus of claim 20 wherein said randomizing means includes means for deriving first and second signals comprising the sum and difference of said multiple channels, respectively; means for delaying one of said first or second signals to produce a third signal; and means for summing said third with the remaining one of said first or second signals.
Claim 24
Dependent Claim
16 words
The apparatus of claim 14 wherein frequency of said multiple channels is limited to preselected ranges.
Claim 25
Dependent Claim
23 words
The apparatus of claim 14 wherein said at least one co-channel is derived substantially only from high frequency components of said multiple channels.
Claim 26
Dependent Claim
42 words
The apparatus of claim 14 wherein said at least one co-channel is derived from information in the low frequency component of said multiple channels; and said at least one encoded channel is generated from the high frequency components of said multiple channels.
Claim 27
Dependent Claim
15 words
The apparatus of claim 23 wherein said high frequency component is above about 1 kilohertz.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-01-10 | 1997-07-12 | 1998-01-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-01-10 | 2001-07-12 | 2002-01-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-01-10 | 2005-07-12 | 2006-01-11 | $7700.00 | Window Closed / Lapsed |