Title of Invention	A CODEC AND A METHOD FOR RECEIVING A DIGITAL TRANSMISSION COMPRISING A PLURALITY OF DIGITAL AUDIO SIGNALS AND FOR SIMULTANEOUS REPRODUCTION OF THESE SIGNALS AS ANALOG AUDIO PROGRAMMES
Abstract	A codec (26) in a processor-based system (10) handles at least two separate audio programs at the same time. This may be useful, for example, for simultaneously playing one audio program while recording another audio program. A first digital to analog converter pair (58) may be coupled to a first mixer (62) and a second digital to analog converter pair (80) may include a second mixer (82). Thus, two separate audio programs may be handled at the same time, each by a separate digital to analog converter and mixer.

Title of Invention

A CODEC AND A METHOD FOR RECEIVING A DIGITAL TRANSMISSION COMPRISING A PLURALITY OF DIGITAL AUDIO SIGNALS AND FOR SIMULTANEOUS REPRODUCTION OF THESE SIGNALS AS ANALOG AUDIO PROGRAMMES

Abstract

A codec (26) in a processor-based system (10) handles at least two separate audio programs at the same time. This may be useful, for example, for simultaneously playing one audio program while recording another audio program. A first digital to analog converter pair (58) may be coupled to a first mixer (62) and a second digital to analog converter pair (80) may include a second mixer (82). Thus, two separate audio programs may be handled at the same time, each by a separate digital to analog converter and mixer.

Full Text	A CODEC AND A METHOD FOR RECEIVING A DIGITAL TRANSMISSION COMPRISING A PLURALITY OF DIGITAL AUDIO SIGNALS AND FOR SIMULTANEOUS REPRODUCTION OF THESE SIGNALS AS ANALOG AUDIO PROGRAMMES Background This invention relates to a codec and a method for receiving a digital transmission comprising a plurality of digital audio signals and for simultaneous reproduction of these signals as analog audio programmes, and relates generally to audio codec for processor-based systems. An audio codec receives digital audio information, converts it to an analog format and mixes that audio information with other data for play by a processor-based system. Generally, the codec is controlled by an audio controller, also known as an audio accelerator, coupled to a bus. The audio accelerator is in turn controlled by the processor. Many processor-based systems are now being used for relatively elaborate audio functions. For example, processor-based systems may be used to receive digital radio, television and stereo system signals and to play those signals in a unified system. Digital television signals may be received through a cable or satellite connection. In addition, processor-based systems may be utilized to record digital audio information received from a variety of sources. Conventional codecs, however, handle one audio program at any one time. For example, the Audio Codec '97 (AC' 97) Specification, Revision 2.1, dated May 22, 1998, available from Intel Corporation, describes an audio codec that receives a digital stereo channel pair and converts that pair into an analog stereo channel pair. The term "pair" refers to the two channels conventionally called the left and the right channels in stereo systems. The converted analog stereo channel pair may be mixed with other information in a mixer within the codec. The mixer is also coupled to an analog to digital converter that provides an output from the mixer to the digital link. The AC 97 codec is amenable to handling only one audio program at a time. It is not amenable, for example, to simultaneously recording and playing a television program. Thus, there is a need for a codec that supports the increasing demands being placed on processor-based systems for handling more than one audio program at a time. Summary of the Invention Accordingly, the present invention provides a codec comprising : a digital interface a plurality of stereo channel pairs; a first pair of digital to analog converters coupled to one of said stereo channel pairs ; a second pair of digital to analog converters coupled to another one of said stereo channel pairs ; a pair of analog mixers each outputting a separate audio program, each of said mixers coupled to one of said first and second pairs of digital to analog converters ; and a pair of analog to digital converters coupled to another one of said stereo channel pairs ; one of said mixers also coupled to said pair of analog to digital converters. The present invention also provides a processor-based system comprising : a processor; an audio accelerator coupled to said processor; a codec coupled to said audio accelerator, said codec comprising a digital interface having a plurality of stereo channel pairs, a first pair of digital analog converters coupled to one of said stereo channel pairs, a second pair of digital-to-analog converters coupled to another one of said stereo channel pairs, and a pair of analog mixers each outputting a separate audio program, each of said mixers coupled to one of said first and second pairs of digital-to- analog converters. The present invention further provides a method for receiving a digital transmission comprising a plurality of digital audio signals and for simultaneous reproduction of these signals as analog audio programmes comprising the steps of : receiving at least two digital audio programs in a codec ; converting each of said digital audio programs to an analog format and mixing each digital program ; and providing an analog output for each audio program. The present invention further provides an article comprising a medium storing instructions that enable a processor-based system to : receive at least two digital audio programs ; convert each of said digital audio programs to an analog format ; output each of said audio programs to a different port; and programmably change the assignment of said programs to said ports. The present invention further provides an article comprising a medium storing instructions that enable a processor-based system to : receive at least two digital audio programs ; convert each of said digital audio programs to an analog format; programmably change the data rate of at least one of said audio programs. Brief Description of the Drawings Figure 1 is a block depiction of a processor-based system, in accordance with one embodiment of the present invention; Figure 2 is a block depiction of the codec of Figure 1, in accordance with one embodiment of the present invention; and Figure 3 is a flow chart for software in accordance with one embodiment of the present invention. Detailed Description A processor-based system 10, shown in Figure 1, may be a conventional desktop, laptop or handheld computer system or a processor-based web appliance device. In one embodiment of the present invention, the system 10 may be a set-top box in which the display 36 is a television receiver. In accordance with one embodiment of the present invention, the system 10 may handle more than one audio program at a time. An audio program is a stereo or monaural file that is received over a digital link. The audio program may include voice, music, or television sound, as examples. In some embodiments of the present invention, the system 10 may play one audio program at the same time it is recording another audio program. The system 10 includes a processor 12 coupled to a north bridge 16. The north bridge 16 couples the system memory 20 and a video and graphics bus 23. The north bridge 16 may include a graphics controller and a memory controller. The bus 22 may be coupled to a decoder 34 that is coupled to the display 36, such as a television receiver or monitor. The decoder 34 may be coupled to a demodulator/tuner 37. The decoder 34 may also include video digital to analog converters and a demultiplexer. The decoder 34 may, for example, decode data compressed according to one of the standards promulgated by the Motion Picture Experts Group, such as for International Organization for Standarisation {Geneva, Switzerland) ISO/TEC 11172 (1993). One compressed television program may be decoded by the decoder 34 so that uncompressed video data is sent to the south bridge 38 over the bus 22. At the same time another program may be processed by the processor 12 and north bridge 16. The south bridge 38 forwards the audio data to the coder/decoder or codec 26 through a digital link 54. In accordance with one embodiment of the present invention, the digital link 54 and the codec 2 6 may be compliant with the AC 97 specification. The codec 26 receives a digital signal over the digital link 54 and provides an analog output to a sound system 30 that includes an amplifier and speakers. The speakers may be a part of a television receiver 36 or other entertainment device. The south bridge 38 also couples a compact disk player 44 and a hard disk drive 42. In one embodiment of the present invention, the hard disk drive 42 may be utilized to record an audio program. For example, the system 10 may record an audio program on the hard disk drive 42 at the same time the system 10 is playing an audio program received from the compact disk player 44. Thus, in some embodiments of the present invention, digital audio programs may be received through the demodulator/tuner 37 which may be coupled, for example to a satellite or cable connection. The received data is forwarded to the decoder 34, which separates video, audio and other data streams and sends audio data to the north bridge 16. One of those audio programs may be recorded, for example on the hard disk drive 42 at the same time another audio program is being played over the sound system 30. In some embodiments of the present invention, a third audio program may be handled by the codec 2 6 at the same time as the other two audio programs. The south bridge 38 may also couple a firmware hub 52 used for booting the system 10. In one embodiment, the hub 52 may be a nonvolatile memory, such as a flash memory, that also stores information such as channel number, volume settings and the like when the system 10 is powered down. Referring to Figure 2, the codec 2 6 receives at least two digital audio programs over the digital link 54. The codec 26 includes a digital interface 56. The digital interface 56 provides a plurality of monaural channels and stereo channel pairs. For example, the digital interface 56 may provide a channel pair to a pair of digital to analog converters 58. Each of the pair of converters 58 may convert one of a left and right stereg channel, in a digital format, to an analog format. A power management module 78 provides power management for the codec 26. Similarly, the digital interface 56 may include a pair of channels that receive an analog input from an analog to digital converter pair 60. Moreover, the digital interface 56 may provide another channel pair to another pair of digital to analog converters 80. Each of the digital to analog converter pairs 58 and 80 are coupled to a different analog mixer 62 or 82. The mixers 62 atnd 82 mix the information from the digital to analog converters 58 and 80, respectively, with other information that may be received by the codec 26. In addition, the mixers 62 and 82 may provide audio gain control. A line output 84 is provided for the mixer 82. Also coupled to the digital interface 56 is a Sony/Phillips digital interconnect format (S/PDIF) formatter 86. The S/PDIF is described in the ISC 60958 (1989) Standard titled, "Digital Audio Interface" (IEC 60958 (1989)) by the International Electrotechnical Commission and available from American National Standards Institute, New York, New York 10036. The formatter 86 may receive an S/PDIF audio program from the digital interface 56 and may provide the program, in appropriate format, to a pair of left and right channels 8 8 and 90. The S/PDIF format carries a stereo channel pair with a sampling rate of up to 45 kilosampl.es per second and a sample precision of up to 24 bits. An S/PDIF physical link uses a biphase Manchester coded stream. Manchester coding combines a data stream, with a clock on a single channel, with up to two transitions on the line for each bit conveyed. There is a line transition at each end of a bit and a central transition if the data is a one. The S/PDIF also carries a subcode that indicates the current track number and current time within the track. In some cases, the digital link 54 may provide data faster than the formatter 8 6 can handle that data. If there is any mismatching between the data sending rate from the data consuming rate, a software driver may be used to apply stuffing data to a pair of slots in the digital interface 56. One of those slots may include a control word that tells whether the data in the two slots are real data or stuffing data. The formatter 86 may also include a phase locked loop circuit for generating signals of the desired frequencies. The formatter 8 6 in some embodiments of the present invention may output the same audio program as the digital to analog converter 80. Alternatively, the formatter 8 6 may handle a third audio program. Audio programs may be swapped, on the fly, between the digital to analog converter pair 80 and the digital to analog converter pair 58 by software. Thus, a first channel may be recorded while watching a second channel. One can easily switch to recording the second channel while watching the first channel, without reconnecting cables to external recording peripherals. In one embodiment of the present invention, the digital link 54 provides stereo pulse code modulated (PCM) signals. The digital to analog converters 58 and 80 may operate at 48 kilohertz. The mixer 62 may receive signals from the digital to analog converter pair 58 as well as from two pairs of stereo channels 70 and 72 and a pair of monaural channels 74 and 76. The various input channels may be mixed and gain control may be provided. The mixer 62 may output a pair of left and right line out channels 64 and 66 and a monaural output 68. Thus, an output signal may be provided to an output jack for a stereo mix of all sources and a headphone jack, as one example. The line input channels 70, 72, 74 and 76 then receive a variety of analog inputs from external sources. The monaural output 68 may, for example, be utilized by a telephone system. One of the line inputs 70 or 72 may also include a signal from the compact disk player 44. The software 92 for controlling the codec 26, in accordance with one embodiment of the present invention is shown in Figure 3. The software 92 may be stored on the hard disk drive 42 in one embodiment. Initially, the software 92 checks, at diamond 94, to determine whether a request has been received to switch the output or input ports of the codec 26. For example, if the user is recording a first audio program on the line out 64 and playing a second audio program through the line out 84 to the display 36, the user may thereafter wish to play the program on the line out 64 on the television and record the program on the line out 84. To do this without having to reconnect the peripheral devices to the different line outs, the user may provide an input to the processor-based system 10 through a graphical user interface. The user may request a switch of the information fed to the various outputs. For example, the processor 12 may control the digital interface 56 and its multiplexer to change the data that is fed to the various output ports of the digital interface 56. Thus, as indicated in Figure 3, when a switch request is received, as determined in diamond 94, it may cause a signal to be sent to the digital interface 56 to change the multiplexer output ports as indicated in block 96. If no switch request is received or after implementing a switch request, a check at block 98 determines whether the data rates of the various components connected to the codec 26 are compatible with the codec's data, rates. If a peripheral device such as one connected to the S/PDIF formatter 86 output lines 88 and 90 is unable to utilize the data rate provided by the codec 26, as determined in diamond 100, the processor 12 may modify the data rates as indicated in block 102. The system 10 may determine that the data rates are incompatible in a number of different fashions. In one case, the codec 2 6 may receive a signal from the processor 12 (or the peripheral device) indicating that the data rate cannot be handled. In another case, the processor 12 may obtain information such as a device ID from each coupled peripheral. Based on a database of available data rates for available components, the processor 12 may determine that the data rate produced by the codec 26 is incompatible with a particular peripheral device. The data rate may be adjusted in a number of ways. In one case, the data rate maybe adjusted in the digital interface 56. The processor 12 may generate a signal that selects a different data rate for a given port in the digital interface 56. The digital interface 56 may include a plurality of data rates for each of a plurality of output ports . In another case, the processor 12 may cause the audio accelerator 24 to provide stuffing to effectively decrease the data rate of data provided to a particular port. In still another case, the formatter 86 may be commanded by the processor 12 to slow the data rate, for example by providing stuffing or other conventional means. While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this presenr invention. What is claimed is: WE CLAIM : 1. A codec comprising : a digital interface a plurality of stereo channel pairs ; a first pair of digital to analog converters coupled to one of said stereo channel pairs; a second pair of digital to analog converters coupled to another one of said stereo channel pairs; a pair of analog mixers each outputting a separate audio program, each of said mixers coupled to one of said first and second pairs of digital to analog converters; and a pair of analog to digital converters coupled to another one of said stereo channel pairs ; one of said mixers also coupled to said pair of analog to digital converters. 2. The codec as claimed in claim 1 comprising a S/PDIF digital interconnect formatter. 3. The codec as claimed in claim 1 wherein said digital interface comprises a plurality of programmable ports so that the connections from the digital interface to said digital-to-analog converters may be changed. 4. The codec as claimed in claim 1 wherein said digital interface has a programmably changeable output data rate. 5. A method for receiving a digital transmission comprising a plurality of digital audio signals and for simultaneous reproduction of these signals as analog audio programmes comprising the steps of: receiving at least two digital audio programs in a codec ; converting each of said digital audio programs to an analog format and mixing each digital program; and providing an analog output for each audio program. 6. The method as claimed in claim 5 comprising receiving a third audio program in a S/PDIF digital interconnect format, formatting said third audio program and outputting said third audio program. 7. The method as claimed in claim 5 comprising outputting each of said audio programs through a different codec port and programmably changing the assignment of said programs to said ports. 8. The method as claimed in claim 5 comprising programmably changing the data rate of at least one of said audio programs. 9. The method as claimed in claim 5 comprising mixing one of said audio programs in analog format with another analog signal. 10. A codec, substantially as herein described, particularly with reference to and as illustrated in the accompanying drawings. 11. A method for receiving a digital transmission comprising a plurality of digital audio signals and for simultaneous reproduction of these signals as analog audio programmes, substantially as herein described, particularly with reference to the accompanying drawings. A codec (26) in a processor-based system (10) handles at least two separate audio programs at the same time. This may be useful, for example, for simultaneously playing one audio program while recording another audio program. A first digital to analog converter pair (58) may be coupled to a first mixer (62) and a second digital to analog converter pair (80) may include a second mixer (82). Thus, two separate audio programs may be handled at the same time, each by a separate digital to analog converter and mixer.

Full Text

A CODEC AND A METHOD FOR RECEIVING A DIGITAL
TRANSMISSION COMPRISING A PLURALITY OF DIGITAL
AUDIO SIGNALS AND FOR SIMULTANEOUS REPRODUCTION
OF THESE SIGNALS AS ANALOG AUDIO PROGRAMMES
Background
This invention relates to a codec and a method for receiving a digital
transmission comprising a plurality of digital audio signals and for
simultaneous reproduction of these signals as analog audio programmes, and
relates generally to audio codec for processor-based systems.
An audio codec receives digital audio information,
converts it to an analog format and mixes that audio
information with other data for play by a processor-based
system. Generally, the codec is controlled by an audio
controller, also known as an audio accelerator, coupled to a
bus. The audio accelerator is in turn controlled by the
processor.
Many processor-based systems are now being used for
relatively elaborate audio functions. For example,
processor-based systems may be used to receive digital
radio, television and stereo system signals and to play
those signals in a unified system. Digital television
signals may be received through a cable or satellite
connection. In addition, processor-based systems may be
utilized to record digital audio information received from a
variety of sources.
Conventional codecs, however, handle one audio program
at any one time. For example, the Audio Codec '97 (AC' 97)
Specification, Revision 2.1, dated May 22, 1998, available
from Intel Corporation, describes an audio codec that
receives a digital stereo channel pair and converts that
pair into an analog stereo channel pair. The term "pair"
refers to the two channels conventionally called the left
and the right channels in stereo systems. The converted
analog stereo channel pair may be mixed with other
information in a mixer within the codec. The mixer is also

coupled to an analog to digital converter that provides an output from the
mixer to the digital link.
The AC 97 codec is amenable to handling only one audio program at a
time. It is not amenable, for example, to simultaneously recording and playing
a television program.
Thus, there is a need for a codec that supports the increasing
demands being placed on processor-based systems for handling more than
one audio program at a time.
Summary of the Invention
Accordingly, the present invention provides a codec comprising : a
digital interface a plurality of stereo channel pairs; a first pair of digital to
analog converters coupled to one of said stereo channel pairs ; a second pair
of digital to analog converters coupled to another one of said stereo channel
pairs ; a pair of analog mixers each outputting a separate audio program,
each of said mixers coupled to one of said first and second pairs of digital to
analog converters ; and a pair of analog to digital converters coupled to
another one of said stereo channel pairs ; one of said mixers also coupled to
said pair of analog to digital converters.
The present invention also provides a processor-based system
comprising : a processor; an audio accelerator coupled to said processor; a
codec coupled to said audio accelerator, said codec comprising a digital
interface having a plurality of stereo channel pairs, a first pair of digital analog
converters coupled to one of said stereo channel pairs, a second pair of
digital-to-analog converters coupled to another one of said stereo channel
pairs, and a pair of analog mixers each outputting a separate audio program,
each of said mixers coupled to one of said first and second pairs of digital-to-
analog converters.

The present invention further provides a method for receiving a digital
transmission comprising a plurality of digital audio signals and for
simultaneous reproduction of these signals as analog audio programmes
comprising the steps of : receiving at least two digital audio programs in a
codec ; converting each of said digital audio programs to an analog format
and mixing each digital program ; and providing an analog output for each
audio program.
The present invention further provides an article comprising a
medium storing instructions that enable a processor-based system to :
receive at least two digital audio programs ; convert each of said digital audio
programs to an analog format ; output each of said audio programs to a
different port; and programmably change the assignment of said programs to
said ports.
The present invention further provides an article comprising a
medium storing instructions that enable a processor-based system to :
receive at least two digital audio programs ; convert each of said digital audio
programs to an analog format; programmably change the data rate of at least
one of said audio programs.
Brief Description of the Drawings
Figure 1 is a block depiction of a processor-based system, in accordance with
one embodiment of the present invention;
Figure 2 is a block depiction of the codec of Figure 1, in accordance with one
embodiment of the present invention; and
Figure 3 is a flow chart for software in accordance with one embodiment of
the present invention.
Detailed Description
A processor-based system 10, shown in Figure 1, may be a conventional
desktop, laptop or handheld computer system or a processor-based web appliance
device. In one embodiment of the present invention, the system 10 may be a set-top
box in which the display 36 is a television receiver.
In accordance with one embodiment of the present invention, the system 10
may handle more than one audio program at a time. An audio program is a stereo or
monaural file that is received over a digital link. The audio program may include
voice, music, or television sound, as examples. In some embodiments of the present
invention, the

system 10 may play one audio program at the same time it is
recording another audio program.
The system 10 includes a processor 12 coupled to a
north bridge 16. The north bridge 16 couples the system
memory 20 and a video and graphics bus 23. The north bridge
16 may include a graphics controller and a memory
controller. The bus 22 may be coupled to a decoder 34 that
is coupled to the display 36, such as a television receiver
or monitor. The decoder 34 may be coupled to a
demodulator/tuner 37. The decoder 34 may also include video
digital to analog converters and a demultiplexer. The
decoder 34 may, for example, decode data compressed
according to one of the standards promulgated by the Motion
Picture Experts Group, such as for International
Organization for Standarisation {Geneva, Switzerland)
ISO/TEC 11172 (1993).
One compressed television program may be decoded by the
decoder 34 so that uncompressed video data is sent to the
south bridge 38 over the bus 22. At the same time another
program may be processed by the processor 12 and north
bridge 16.
The south bridge 38 forwards the audio data to the
coder/decoder or codec 26 through a digital link 54. In
accordance with one embodiment of the present invention, the
digital link 54 and the codec 2 6 may be compliant with the
AC 97 specification. The codec 26 receives a digital signal
over the digital link 54 and provides an analog output to a
sound system 30 that includes an amplifier and speakers.
The speakers may be a part of a television receiver 36 or
other entertainment device.
The south bridge 38 also couples a compact disk player
44 and a hard disk drive 42. In one embodiment of the
present invention, the hard disk drive 42 may be utilized to

record an audio program. For example, the system 10 may
record an audio program on the hard disk drive 42 at the
same time the system 10 is playing an audio program received
from the compact disk player 44.
Thus, in some embodiments of the present invention,
digital audio programs may be received through the
demodulator/tuner 37 which may be coupled, for example to a
satellite or cable connection. The received data is
forwarded to the decoder 34, which separates video, audio
and other data streams and sends audio data to the north
bridge 16. One of those audio programs may be recorded, for
example on the hard disk drive 42 at the same time another
audio program is being played over the sound system 30. In
some embodiments of the present invention, a third audio
program may be handled by the codec 2 6 at the same time as
the other two audio programs.
The south bridge 38 may also couple a firmware hub 52
used for booting the system 10. In one embodiment, the hub
52 may be a nonvolatile memory, such as a flash memory, that
also stores information such as channel number, volume
settings and the like when the system 10 is powered down.
Referring to Figure 2, the codec 2 6 receives at least
two digital audio programs over the digital link 54. The
codec 26 includes a digital interface 56. The digital
interface 56 provides a plurality of monaural channels and
stereo channel pairs. For example, the digital interface 56
may provide a channel pair to a pair of digital to analog
converters 58. Each of the pair of converters 58 may
convert one of a left and right stereg channel, in a digital
format, to an analog format. A power management module 78
provides power management for the codec 26.
Similarly, the digital interface 56 may include a pair
of channels that receive an analog input from an analog to

digital converter pair 60. Moreover, the digital interface
56 may provide another channel pair to another pair of
digital to analog converters 80. Each of the digital to
analog converter pairs 58 and 80 are coupled to a different
analog mixer 62 or 82. The mixers 62 atnd 82 mix the
information from the digital to analog converters 58 and 80,
respectively, with other information that may be received by
the codec 26. In addition, the mixers 62 and 82 may provide
audio gain control. A line output 84 is provided for the
mixer 82.
Also coupled to the digital interface 56 is a
Sony/Phillips digital interconnect format (S/PDIF) formatter
86. The S/PDIF is described in the ISC 60958 (1989)
Standard titled, "Digital Audio Interface" (IEC 60958
(1989)) by the International Electrotechnical Commission and
available from American National Standards Institute, New
York, New York 10036. The formatter 86 may receive an
S/PDIF audio program from the digital interface 56 and may
provide the program, in appropriate format, to a pair of
left and right channels 8 8 and 90.
The S/PDIF format carries a stereo channel pair with a
sampling rate of up to 45 kilosampl.es per second and a
sample precision of up to 24 bits. An S/PDIF physical link
uses a biphase Manchester coded stream. Manchester coding
combines a data stream, with a clock on a single channel,
with up to two transitions on the line for each bit
conveyed. There is a line transition at each end of a bit
and a central transition if the data is a one. The S/PDIF
also carries a subcode that indicates the current track
number and current time within the track.
In some cases, the digital link 54 may provide data
faster than the formatter 8 6 can handle that data. If there
is any mismatching between the data sending rate from the

data consuming rate, a software driver may be used to apply
stuffing data to a pair of slots in the digital interface
56. One of those slots may include a control word that
tells whether the data in the two slots are real data or
stuffing data. The formatter 86 may also include a phase
locked loop circuit for generating signals of the desired
frequencies.
The formatter 8 6 in some embodiments of the present
invention may output the same audio program as the digital
to analog converter 80. Alternatively, the formatter 8 6 may
handle a third audio program.
Audio programs may be swapped, on the fly, between the
digital to analog converter pair 80 and the digital to
analog converter pair 58 by software. Thus, a first channel
may be recorded while watching a second channel. One can
easily switch to recording the second channel while watching
the first channel, without reconnecting cables to external
recording peripherals.
In one embodiment of the present invention, the digital
link 54 provides stereo pulse code modulated (PCM) signals.
The digital to analog converters 58 and 80 may operate at 48
kilohertz.
The mixer 62 may receive signals from the digital to
analog converter pair 58 as well as from two pairs of stereo
channels 70 and 72 and a pair of monaural channels 74 and
76. The various input channels may be mixed and gain
control may be provided. The mixer 62 may output a pair of
left and right line out channels 64 and 66 and a monaural
output 68. Thus, an output signal may be provided to an
output jack for a stereo mix of all sources and a headphone
jack, as one example. The line input channels 70, 72, 74
and 76 then receive a variety of analog inputs from external
sources. The monaural output 68 may, for example, be

utilized by a telephone system. One of the line inputs 70
or 72 may also include a signal from the compact disk player
44.
The software 92 for controlling the codec 26, in
accordance with one embodiment of the present invention is
shown in Figure 3. The software 92 may be stored on the
hard disk drive 42 in one embodiment.
Initially, the software 92 checks, at diamond 94, to
determine whether a request has been received to switch the
output or input ports of the codec 26. For example, if the
user is recording a first audio program on the line out 64
and playing a second audio program through the line out 84
to the display 36, the user may thereafter wish to play the
program on the line out 64 on the television and record the
program on the line out 84. To do this without having to
reconnect the peripheral devices to the different line outs,
the user may provide an input to the processor-based system
10 through a graphical user interface. The user may request
a switch of the information fed to the various outputs. For
example, the processor 12 may control the digital interface
56 and its multiplexer to change the data that is fed to the
various output ports of the digital interface 56.
Thus, as indicated in Figure 3, when a switch request
is received, as determined in diamond 94, it may cause a
signal to be sent to the digital interface 56 to change the
multiplexer output ports as indicated in block 96.
If no switch request is received or after implementing
a switch request, a check at block 98 determines whether the
data rates of the various components connected to the codec
26 are compatible with the codec's data, rates. If a
peripheral device such as one connected to the S/PDIF
formatter 86 output lines 88 and 90 is unable to utilize the
data rate provided by the codec 26, as determined in diamond

100, the processor 12 may modify the data rates as indicated
in block 102.
The system 10 may determine that the data rates are
incompatible in a number of different fashions. In one
case, the codec 2 6 may receive a signal from the processor
12 (or the peripheral device) indicating that the data rate
cannot be handled. In another case, the processor 12 may
obtain information such as a device ID from each coupled
peripheral. Based on a database of available data rates for
available components, the processor 12 may determine that
the data rate produced by the codec 26 is incompatible with
a particular peripheral device.
The data rate may be adjusted in a number of ways. In
one case, the data rate maybe adjusted in the digital
interface 56. The processor 12 may generate a signal that
selects a different data rate for a given port in the
digital interface 56. The digital interface 56 may include
a plurality of data rates for each of a plurality of output
ports .
In another case, the processor 12 may cause the audio
accelerator 24 to provide stuffing to effectively decrease
the data rate of data provided to a particular port. In
still another case, the formatter 86 may be commanded by the
processor 12 to slow the data rate, for example by providing
stuffing or other conventional means.
While the present invention has been described with
respect to a limited number of embodiments, those skilled in
the art will appreciate numerous modifications and
variations therefrom. It is intended that the appended
claims cover all such modifications and variations as fall
within the true spirit and scope of this presenr invention.
What is claimed is:

WE CLAIM :
1. A codec comprising :
a digital interface a plurality of stereo channel pairs ;
a first pair of digital to analog converters coupled to one of said stereo
channel pairs;
a second pair of digital to analog converters coupled to another one of said
stereo channel pairs;
a pair of analog mixers each outputting a separate audio program, each of
said mixers coupled to one of said first and second pairs of digital to analog
converters; and
a pair of analog to digital converters coupled to another one of said stereo
channel pairs ; one of said mixers also coupled to said pair of analog to digital
converters.
2. The codec as claimed in claim 1 comprising a S/PDIF digital interconnect
formatter.
3. The codec as claimed in claim 1 wherein said digital interface comprises a
plurality of programmable ports so that the connections from the digital interface to
said digital-to-analog converters may be changed.
4. The codec as claimed in claim 1 wherein said digital interface has a
programmably changeable output data rate.
5. A method for receiving a digital transmission comprising a plurality of digital
audio signals and for simultaneous reproduction of these signals as analog audio
programmes comprising the steps of:
receiving at least two digital audio programs in a codec ;
converting each of said digital audio programs to an analog format and
mixing each digital program; and
providing an analog output for each audio program.

6. The method as claimed in claim 5 comprising receiving a third audio
program in a S/PDIF digital interconnect format, formatting said third audio program
and outputting said third audio program.
7. The method as claimed in claim 5 comprising outputting each of said
audio programs through a different codec port and programmably changing the
assignment of said programs to said ports.
8. The method as claimed in claim 5 comprising programmably changing the
data rate of at least one of said audio programs.
9. The method as claimed in claim 5 comprising mixing one of said audio
programs in analog format with another analog signal.
10. A codec, substantially as herein described, particularly with reference to
and as illustrated in the accompanying drawings.
11. A method for receiving a digital transmission comprising a plurality of digital
audio signals and for simultaneous reproduction of these signals as analog audio
programmes, substantially as herein described, particularly with reference to the
accompanying drawings.

A codec (26) in a processor-based system (10) handles at least two
separate audio programs at the same time. This may be useful, for example,
for simultaneously playing one audio program while recording another audio
program. A first digital to analog converter pair (58) may be coupled to a first
mixer (62) and a second digital to analog converter pair (80) may include a
second mixer (82). Thus, two separate audio programs may be handled at the
same time, each by a separate digital to analog converter and mixer.

Documents:

in-pct-2002-1395-kol-granted-abstract.pdf

in-pct-2002-1395-kol-granted-assignment.pdf

in-pct-2002-1395-kol-granted-claims.pdf

in-pct-2002-1395-kol-granted-correspondence.pdf

in-pct-2002-1395-kol-granted-description (complete).pdf

in-pct-2002-1395-kol-granted-drawings.pdf

in-pct-2002-1395-kol-granted-examination report.pdf

in-pct-2002-1395-kol-granted-form 1.pdf

in-pct-2002-1395-kol-granted-form 18.pdf

in-pct-2002-1395-kol-granted-form 2.pdf

in-pct-2002-1395-kol-granted-form 3.pdf

in-pct-2002-1395-kol-granted-form 5.pdf

in-pct-2002-1395-kol-granted-gpa.pdf

in-pct-2002-1395-kol-granted-reply to examination report.pdf

in-pct-2002-1395-kol-granted-specification.pdf

in-pct-2002-1395-kol-granted-translated copy of priority document.pdf

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Patent Number

229501

Indian Patent Application Number

IN/PCT/2002/1395/KOL

PG Journal Number

08/2009

Publication Date

20-Feb-2009

Grant Date

18-Feb-2009

Date of Filing

12-Nov-2002

Name of Patentee

INTEL CORPORATION

Applicant Address

2200 MISSION COLLEGE BOULEVARD, SANTA CLARA, CA 95052

Inventors:

#	Inventor's Name	Inventor's Address
1	MISHRA ANIMESH	1313 CHEWPON AVENUE MILPITAS, CA 95035
2	SHI JUN	6121 YEADON WAY, SAN JOSE, CA 95119

PCT International Classification Number

H04H 7/00

PCT International Application Number

PCT/US01/14255

PCT International Filing date

2001-05-02

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	09/577,399	2000-05-22	U.S.A.