Coded data generation or conversion – Digital code to digital code converters – Data rate conversion
Reexamination Certificate
2000-11-02
2001-05-29
Young, Brian (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
Data rate conversion
C382S232000
Reexamination Certificate
active
06239728
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Field of Invention
This invention pertains to a method and apparatus for encoding data at one of several data rates and more particularly to a method and apparatus which allows the data so encoded to be decoded at two or more rates. The scheme or method and apparatus is particularly useful in the transmission and storage of audio or video information.
B. Description of the Prior Art
Audio programs are often transmitted or recorded as digital data by converting the analog signals. In order to achieve high quality sound a sampling rate is used to sample the analog signal being transmitted or recorded and a high number of bits is used to represent each sample. For example, for CD recordings, or CD quality signal transmissions, sampling rates of up to 96 KHz and 192 KHz are used and each sample is converted to 20-24 bits. One disadvantage of this process is that, in some instances, a high quality sound may not be desired by the customer or his equipment may not be capable a replaying efficiently enough and a low sampling rate of 32 or 48 KHz and an A/D conversion rate of 8-16 bits/sample may be sufficient. Therefore, much of the data produced by the high quality conversion is unnecessary. Therefore it is desirable to have an encoding scheme which allows the transmittal or recording of signals at a very high quality, but which also allows these signals to be received or playback selectively either at the same high quality as they were transmitted or recorded, or at a lower quality.
A further disadvantage of existing encoding schemes is that they are highly inefficient and hence require a high band width to transmit or record unless complex compression algorithms are used.
OBJECTIVES AND SUMMARY OF THE INVENTION
Therefore it is an objective of the present invention to provide an encoding scheme for encoding signals sampled at a high sampling rate such that the encoded signals can be decoded selectively at several different effective rates.
A farther objective of the present invention to provide an encoding method which automatically compresses the signals as well, thereby requiring less bandwidth than prior art encoding schemes.
A further objective is to provide an encoding scheme and apparatus which can encode a series of signals into encoded signals on two or more channels that are self-clocking.
Yet a further objective is to provide a single apparatus which can record signals at several different rates and sound qualities simultaneously from a high quality single source.
A further objective is to provide a data transmission and or recording device using an encoding scheme which allows the encoded data to be only partially decoded or read, to generate a lower quality sound.
Other objectives and advantages of the invention shall become apparent from the following description. Briefly, an analog signal is encoded in accordance with this invention by sampling said signal at a relatively high sampling rate and converting the samples into a series of digital signals. A differential encoding process is then used to generate an encoded series consisting of every n-th signal of the original series and intermediate signals which are determined from the difference of some of the original signals. In its simplest form, the encoding scheme converts a series A of digital signals A
1
, A
2
, A
3
, into two series A′ and B. Series A′ consists of every second term of the original series, such as A
1
, A
3
, A
5
. . . . The second series B consists of intermediate terms B
1
, B
2
, B
3
wherein each term is related to the difference between one term of the series A′ and one term of the original series A which is not present in series A′. For example, B
1
=A
1
-A
2
, B
2
=A
3
-A
4
and so on. The two series A,′ B can be interleaved, or can be transmitted or recorded on separate channels.
The signals encoded by the inventive scheme can be recorded or can be transmitted to one or more receiving stations by broadcasting and other similar means. At each receiver, or to play the signals back from a recorded medium, the original signal can be accurately reconstructed by generating the original series A from series A′ and B. Alternatively, a lower quality signal may be generated by omitting at least some of the signals of series B.
REFERENCES:
patent: 4477903 (1984-10-01), Schouhamer Immink et al.
patent: 4567518 (1986-01-01), Driessen
patent: 5371842 (1994-12-01), Easton et al.
patent: 5438635 (1995-08-01), Richards
McPherson Alan J.
Thagard Gregory B.
Gottlieb Rackman & Reisman P.C.
Nguyen John
Warner Music Group Inc.
Young Brian
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