HK1064239B - Apparatus and method for reducing power consumption in a mobile unit - Google Patents

Description

Apparatus and method for reducing power consumption in a mobile unit

Technical Field

The present invention relates generally to an apparatus and method for conserving power in a mobile unit, and more particularly to conserving power in a stereo audio codec used in a mobile unit.

Background

Traditionally, mobile units such as cellular telephones have been used primarily for analog communications such as FM radio transmissions. Currently, digital communications such as code division multiple access ("CDMA") are the primary form of transmission because they allow more users to occupy bandwidth while improving voice quality and reliability.

For digital communication techniques used on the reverse link, audio signals such as voice must be converted from analog to digital signals. On the forward link, instead, the received digital signal must be converted to an analog signal for playback by the mobile unit speaker. An audio encoder/decoder capable of analog/digital conversion in two directions is generally referred to as a "codec". Codecs are commonly used in various mobile units, such as cellular telephones.

As is known in the art, mobile units such as cellular telephones typically operate on batteries. Extended battery life is a desirable feature in today's cellular telephone market. In addition to long battery life, attractive products must have up-to-date features that compete with the opposing manufacturers, such as the ability to play music.

New features like music performance are becoming increasingly popular in current cellular phones where users can listen to MP3 audio. Such devices require a stereo codec rather than the mono codec found in older cellular telephones.

The exemplary stereo audio codec of fig. 1 may be part of a digital cellular telephone capable of playing stereo audio. The stereo audio codec 101 converts the audio analog signal to a digital signal for transmission in the reverse link. The stereo audio codec 101 is also used to convert digital signals into audio analog signals for outputting the caller's voice over a telephone speaker in the forward link or for playing audio.

The exemplary stereo audio codec 101 consists of two audio processing paths 116 and 118. For example, the transmit audio processing path 116 is used to convert the user's analog voice signal into a digital voice signal. The transmit audio processing path 116 is briefly described below.

The speech signal output may originate from a mobile unit microphone 132, a headset microphone 134, or an auxiliary input 136, each of which is connected to the stereo audio codec 101 via an I/O jack 128. The I/O jack 128 provides an input to a first microphone amplifier 138, and the amplifier 138 amplifies the input analog signal. The output analog signal of the first microphone amplifier 138 may optionally be amplified again by the second microphone amplifier 142 and/or filtered by a high pass filter and gain 144 depending on the input type. For example, optional filtering may be performed on the auxiliary input 136.

The multiplexer 146 may select the output of the high pass filter and gain 144 or may select the output of the first microphone amplifier 138. The output of the multiplexer 146 is coupled to an analog-to-digital converter 148, which converts the input analog speech signal to a digital speech signal. To the right of the separation line 105 is a digital signal. The digital voice signal is then filtered by a transmit filter 150 and amplified by a transmit gain 152 to produce a transmitted voice pulse code modulation ("PCM") 153. The transmitted voice PCM is sent to PCM interface 122 and then sent for further processing, such as voice compression via PCM "input" signal 154.

The receive audio processing path 118 is similar to the transmit audio processing path 116 except that the signals flow in opposite directions and there are two signal paths for the left and right channels. The PCM "out" signal 155 interfaces with the stereo audio codec 101 through the PCM interface 122. "output" within PCM "output" signal 155 refers to "output samples" that ultimately arrive at one or more speaker outputs having: earpiece speaker 123, left headphone speaker 124, and/or right headset speaker 126.

If PCM "out" signal 155 is stereo, PCM interface 122 splits the signal between left channel digital signal 156 and right channel digital signal 157 for separate processing. The left channel digital signal 156 is amplified by a receive gain 162 and filtered by a receive filter 164. The output of the receive filter 164 is then converted to an analog output by a digital-to-analog converter 170. To the left of the split line 105 is an analog signal. The same processing of the reception gain 166, the reception filter 168, and the digital-to-analog converter 172 is also performed for the right channel.

Left and right channel digital-to-analog converters 174 and 176, respectively, provide inputs to an audio output multiplexer 178. The audio output multiplexer 178 directs the analog output either to a headphone amplifier 181 or to left and right headphone amplifiers 180 and 182, respectively, depending on what type of audio output device is connected or not connected to the I/O jack 128.

Stereo audio codecs consume substantially more power than mono audio codecs, which are used in previous generations of cellular telephones. Since the stereo codec has an additional audio processing path to produce the left and right channels, as shown by the receive audio processing path 118, it consumes about 45% more power than the mono audio codec.

If the PCM output signal 155 is mono and a mono headset is attached, it is desirable to have one channel within the receive audio processing path 118 enabled (i.e., on) and the other channel disabled (i.e., off). For example, if the right channel is a "non-default" channel, it may be desirable to disable the right channel, including components such as receive gain 166, receive filter 168, and digital-to-analog converter 172.

However, according to known techniques employed within stereo audio codecs, there is no way to conserve power by turning off the audio processing components of the "non-default" channel, such as the receive gain 166, the receive filter 168, and the digital-to-analog converter 172 in the right channel.

Similarly, when stereo headset speakers are connected to the I/O jack 128 and the PCM output signal 155 is mono, it is not normal for a user to hear speech in only one speaker of the stereo headphones if the PCM output signal 155 is mono. For the system of fig. 1, a known method of playing the mono signal on two loudspeakers is to simply copy the mono signals of the left and right channels at 156 and 157. In this approach, the left channel receive gain 162, receive filter 164, and digital-to-analog converter 170 will be turned on, and the corresponding right channel components: the receive gain 166, receive filter 168 and digital to analog converter 172 are also turned on. However, although this method is easy to implement, both of its stereo processing paths consume power.

Unless novel techniques for conserving power within a stereo audio codec are used, mobile units such as cellular telephones may have short battery lives, which may result in poor sales and user dissatisfaction. There is therefore a need in the art for efficient power management of stereo codecs within mobile units such as cellular telephones.

Disclosure of Invention

According to one aspect of the invention, an embodiment of the invention is a mobile unit that includes a codec, a vocoder, and an audio decoder. The vocoder and audio decoder provide respective outputs to the audio multiplexer. The stereo/mono control unit receives an audio multiplexer input from the audio multiplexer. The stereo/mono control unit provides control outputs to the codec to reduce power consumption within the codec and thus within the mobile unit.

The control output produced by the stereo/mono control unit is coupled to a plurality of components within a received audio processing path of the codec. For example, the control output may be coupled to: receive gain in the right channel of the receive audio processing path, a receive filter, a digital-to-analog converter, a left/right selector, and a headphone amplifier.

For example, by disabling at least one component in the right channel of the codec receive audio processing path, the control output of the stereo/mono control unit may result in significant power savings. For example, such disabling may occur when the audio multiplexer input received by the stereo/mono control unit contains a speech signal instead of a music signal.

Drawings

Fig. 1 illustrates an example of a known codec.

Fig. 2 illustrates an embodiment of the invention using a stereo/mono control unit in conjunction with a codec.

Fig. 3 illustrates further details of the codec shown in fig. 2.

FIG. 4 is a flow chart describing the operation of an embodiment of the present invention.

Detailed Description

The disclosed embodiments are directed to an apparatus and method for reducing power consumption in a mobile unit. Referring now to fig. 2, a block 200 illustrates a portion of a mobile unit, such as a cellular telephone, for illustrating certain features of the present invention. Although block 200 shows only a portion of a mobile unit, block 200 is referred to herein as mobile unit 200. Note that a "mobile unit" may be a single chip, also referred to as a "device" in the present invention; alternatively, the mobile unit may be a collection of discrete devices and other components, such as a cellular telephone. Furthermore, although an embodiment of the present invention is described throughout this application with reference to a "mobile unit", it is clear that the present application applies equally to "non-mobile units" and "non-mobile devices".

Mobile unit 200 includes an antenna 209 for receiving Radio Frequency (RF) signals from a base transceiver station 214 via a base station antenna 213. The RF block 208 demodulates and downconverts the received RF signal for baseband processing. Some baseband processing blocks are not shown in fig. 2. The baseband output of the RF block 208 may include compressed voice packets. The compressed voice packets output by the RF block 208 are provided to the vocoder 206. Vocoder 206 decompresses the compressed voice packets received from the mobile unit baseband processing, which is not shown in fig. 2. The decompressed speech output of the vocoder 206 provides an input to the audio multiplexer 222.

The audio multiplexer 222 may also accept input from the audio decoder 220. The audio decoder 220 decompresses compressed audio formats such as, by way of non-exhaustive example, MPEG layer 3(MP3) compressed audio. The audio decoder 220 may output stereo or mono audio to an audio multiplexer 222.

The audio multiplexer 222 provides the PCM input to the stereo audio codec 201 via a PCM "out" signal 255. If the PCM output signal 255 is stereo, the audio signal is split into two audio streams, a left channel digital signal 256 and a right channel digital signal 257. The left channel digital signal 256 and the right channel digital signal 257 are input to the receive audio processing path 218, which converts the signals from digital audio signals to analog audio signals. The audio analog signals are then output to headphone speaker 223 or left and right headset speakers 224 and 226, which are connected to I/O jack 228.

On the reverse link, a user may enter speech through the mobile unit microphone 232, the headset microphone 234, or the auxiliary input 236 connected to the I/O jack 228. The I/O jack 228 provides an analog voice signal as an input to the transmit audio processing path 216 of the stereo audio codec 201. The transmit audio processing path 216 converts the analog input signal to a PCM "in" signal 254. The stereo audio codec 201 provides a PCM "input" signal 254 as an input to the vocoder 206 for voice compression. The voice packets compressed by the vocoder 206 are input to the RF block 208. The data is upconverted and modulated onto a carrier wave by an RF block 208 for RF transmission via an antenna 209. The base station antenna 213 receives the RF transmission and the base station transceiver 214 processes the received RF transmission.

According to an embodiment of the invention, stereo/mono control unit 210 receives audio multiplexer input 298 from audio multiplexer 222. The stereo/mono control unit 210 also receives a plug-in detection input 292 from the plug-in detection circuit 212. The plug-in detection circuit 212, in turn, receives I/O inputs 294 from the I/O sockets 228. As shown in fig. 2, the control output 296 of the stereo/mono control unit 210 is coupled to a stereo audio codec 201.

Fig. 3 shows the stereo audio codec 201 in more detail. The exemplary stereo audio codec 301 consists of two audio processing paths 316 and 318. Transmit audio processing path 316 is used to convert the user's analog voice signal into a digital voice signal. The transmit audio processing path 316 is described below.

The voice signal input may originate from a mobile unit microphone 332, a headset microphone 334, or an auxiliary input 336, which are connected to the stereo audio codec 301 via an I/O jack 328. The I/O jack 328 provides an input to a first microphone amplifier 338, which amplifies the input analog signal. The output analog signal of the first microphone amplifier 338 may optionally be amplified again by the second microphone amplifier 342 and/or filtered by a high pass filter and gain 344 depending on the input type. For example, the auxiliary input 336 may be optionally filtered.

The multiplexer 346 may select the output of the high pass filter and gain 344, or it may select the output of the first microphone amplifier 338. The output of the multiplexer 346 is coupled to an analog-to-digital converter 348, which converts the input analog speech signal to a digital speech signal. The signal to the right of the division line 305 is a digital signal. The digital speech signal is then filtered by transmit filter 350 and amplified by transmit gain 352 to produce transmitted speech PCM 353. The transmitted voice PCM 353 is sent to the PCM interface 322, which is then sent for further processing, such as voice compression via the PCM "input" signal 354.

The receive audio processing path 318 is similar to the transmit audio processing path 316 except that the signals flow in opposite directions and there are two signal paths for the left and right channels. The PCM "out" signal 355 interfaces with the stereo audio codec 301 via the PCM interface 322.

If the PCM output signal 355 is stereo, the PCM interface 322 splits the PCM output signal 355 between the left channel digital signal 356 and the right channel digital signal 357 for separate processing within the receive audio processing path 318. The left channel digital signal 356 is amplified by a receive gain 362, which may provide volume control. The output of the receive gain 362 is filtered by a receive filter 364, which may provide interpolation of the signal. The digital signal output of the receive filter 364 is converted to a left channel audio analog signal 374 by a digital to analog converter 370. The signal to the left of the split line 305 is an analog signal. The same audio processing is done for the right channel with audio processing components, these components are: receive gain 366, receive filter 368, and digital-to-analog converter 372.

The left and right channel analog audio signals 374 and 376, respectively, provide inputs to an audio output multiplexer 378. Audio output multiplexer 378 directs the analog output either to headphone amplifier 381 or to left and right headphone amplifiers 380 and 382, respectively, depending on whether headphone speaker 323, left headphone speaker 324, or headphone speaker 326 is connected to I/O jack 328.

The plug-in detection unit 312 receives I/O input 394 from I/O socket 328. The plug-in detection unit 312 determines the type of audio output device or devices connected to the I/O socket 328. The plug-in detection circuit 312 provides a plug-in detection input 392 to the stereo/mono control unit 310. Stereo/mono control unit 310 provides control output 396 to right channel audio processing components including receive gain 366, receive filter 368, digital to analog converter 372, left/right selector 388, and right headset amplifier 382. The left channel analog audio signal 374 and the right channel analog audio signal 376 may be passed through an audio output multiplexer 378 to a left/right selector 388. Control output 396 determines the output of left/right selector 388, the output of which is coupled to right headset amplifier 382.

The stereo/mono control unit 210 is used to enable or disable audio processing components in the right channel (i.e., the "non-default" channel) for saving power in the stereo audio codec 201. As discussed below, during mono audio applications, stereo/mono control unit 210 turns off certain components within receive audio processing path 218. The stereo/mono controller 210 determines whether the current audio application is mono based on whether the audio multiplexer input 298 is music, speech, or otherwise, and whether the audio output device connected to the I/O jack 228 has mono or stereo capabilities.

Typically, for mono audio applications, the audio processing components of the "non-default" channel (i.e., the right channel in this exemplary embodiment) may be disabled, since only one audio processing channel is needed for mono operation. In the present exemplary embodiment, the exemplary stereo audio codec 201 uses the left channel as the "default" mono channel.

As described above, the stereo/mono control unit 210 has two inputs: an audio multiplexer input 298, and a plug-in detection input 292. Audio multiplexer input 298 may be speech, stereo music, mono music, or others. The plug-in detection input 292 may be either stereo or mono. Some examples of many possible combinations of stereo/mono control unit 210 inputs are described below.

The first input combination occurs when the audio multiplexer input 298 is stereo music and the plug-in detection input 292 is stereo. Since the audio output devices connected to the I/O jacks 228 are stereo, it is desirable to enable both the left headset speaker 224 and the right headset speaker 226. Also, since the audio multiplexer input 298 is stereo music, it is desirable to enable both left and right channel audio processing components. As shown in fig. 3, the left audio processing component includes a receive gain 362, a receive filter 364, and a digital-to-analog converter 370, while the right audio processing component includes a receive gain 366, a receive filter 368, and a digital-to-analog converter 372. In this first combination, stereo/mono control unit 310 provides control output 396 to ensure that the right audio processing components are all enabled. Likewise, stereo/mono control unit 310 provides a control output 396 to left/right selector 388 such that right analog audio signal 376 is output from left/right selector 388.

The second input combination occurs when the audio multiplexer input 298 is stereo music and the plug-in detection input 292 is mono. Since the audio output device connected to the I/O jack 228 is mono, the left headset speaker 224 should be enabled and the right headset speaker 226 should be disabled. Also, since the audio multiplexer input 298 is stereo music, the stereo channels may be added together in the digital domain and input to the left channel receive audio processing path according to user preferences or audio application. For example, the left channel digital signal 356 and the right channel digital signal 357 may be digitally added together and input to a left channel receive audio processing component that begins with a receive gain 362. Since the right channel receiving audio processing components need not be enabled, stereo/mono control unit 310 should provide control output 396 such that the right audio processing components are all disabled.

A third input combination occurs when the audio multiplexer input 298 is speech or monophonic music and the plug-in detects that the input 292 is monophonic. Since the audio output device connected to the I/O jack 228 is mono, the left headset speaker 224 should be enabled and the right headset speaker 226 should be disabled. Likewise, since the audio multiplexer input 298 is speech or monophonic music, the left channel audio processing components should be enabled and all right channel audio processing components should be disabled. Thus, in fig. 3, stereo/mono control unit 310 provides control output 396 such that the right audio processing components are all disabled, i.e., receive gain 366, receive filter 368, digital-to-analog converter 372, and right headphone amplifier 382.

A fourth input combination occurs when the audio multiplexer input 298 is speech or mono music and the plug-in detects input 292 is stereo. Since the audio output device connected to the I/O jack 228 is stereo, the left headset speaker 224 should be enabled and the right headset speaker 226 should also be enabled. Likewise, since the audio multiplexer input 298 is speech or monophonic music, the left channel audio processing component should be enabled and the right channel audio processing component should be disabled: receive gain 366, receive filter 368, and digital-to-analog converter 372. Thus, in fig. 3, stereo/mono control unit 310 provides control output 396 such that right channel receive gain 366, receive filter 368, digital-to-analog converter 372 are all disabled, while right headphone amplifier 382 is enabled. Likewise, stereo/mono control unit 310 provides a control output 396 to left/right selector 388 such that left analog audio signal 374 is the output of left/right selector 388.

For the remaining input combinations, stereo/mono control unit 310 may enter a default mode. In the default mode, stereo/mono control unit 310 provides control output 396 such that right channel receive gain 366, receive filter 368, digital-to-analog converter 372, and right headphone 382 are all disabled.

Control output 396 may be comprised of multiple control signals, but for simplicity all control signals are given by a single control output 396. For example, digital to analog converters are typically implemented in hardware, and thus control output 396 may be a simple enable/disable connection type. However, receive gain 366 and receive filter 368 may be implemented within a digital signal processor. In this case, control output 396 may not be a simple disable signal as in the case of a digital-to-analog converter, and control output 396 may be a command to a digital signal processor to enable or disable the firmware portion of receive gain 366 and receive filter 368.

The flowchart in fig. 4 describes exemplary operations of an embodiment of the present invention. When a mobile unit, such as a cellular phone, begins to power up or if the mobile unit is reset, stereo/mono control unit 210 begins the procedure at step 402. In step 404, stereo/mono control unit 210 receives a digital audio signal from audio multiplexer 222 via audio multiplexer input 298. The input digital audio signal may originate from either the vocoder 206 or the audio decoder 220. Depending on the audio application or user selection, either vocoder 206 or audio decoder 220 may be selected as the current input via audio multiplexer 222. After step 404, the stereo/mono control unit 210 proceeds to step 406.

In step 406, stereo/mono control unit 210 determines whether stereo capable headsets or speakers are plugged into I/O jack 228. Stereo-capable headsets or speakers are examples of what are generally referred to in this application as "stereo output components". I/O jack 228 provides I/O input 294 to plug-in detection circuit 212, which in turn provides plug-in detection input 292 to stereo/mono control unit 210. If the plug-in detection circuit 212 detects that a stereo headset has been plugged in, the stereo/mono control unit 210 proceeds to step 410, otherwise it proceeds to step 408.

In step 408, stereo/mono control unit 210 determines whether audio multiplexer input 298 is speech. If stereo/mono control unit 210 determines that audio multiplexer input 298 is speech, stereo/mono control unit 210 proceeds to step 410, otherwise it proceeds to step 412.

In step 410, stereo/mono control unit 210 disables the right channel audio processing component. Stereo/mono control unit 210 outputs control output 396 such that the right audio processing components, receive gain 366, receive filter 368, digital-to-analog converter 372, and right headset amplifier 382, are disabled. After step 410, stereo/mono control unit 210 reaches the end of the procedure at step 418.

In step 412, stereo/mono control unit 210 determines whether audio multiplexer input 298 is music. If the audio multiplexer input 298 is music, the stereo/mono control unit 210 proceeds to step 413, otherwise it proceeds to step 416.

In step 413, stereo/mono control unit 210 determines whether the music signal from audio multiplexer input 298 is stereo. If the music signal from the audio multiplexer input 298 is stereo, the stereo/mono control unit 210 proceeds to step 414, otherwise it proceeds to step 410.

In step 414, stereo/mono control unit 210 outputs control output 396 such that the right audio processing components, receive gain 366, receive filter 368, digital-to-analog converter 372, and right headset amplifier 382, are enabled. In this example, the left channel is "default" mono, and thus the left channel would be enabled for mono or stereo audio applications by default. After step 414, stereo/mono control unit 210 reaches the end of the procedure at step 418.

In step 416, stereo/mono control unit 210 outputs control output 396 such that the right audio processing components, receive gain 366, receive filter 368, digital-to-analog converter 372, and right headset amplifier 382, are disabled. As described above, the left channel is "default" mono, and thus the left channel may be enabled for mono or stereo audio applications by default. After step 416, stereo/mono control unit 210 reaches the end of the procedure at step 418.

In accordance with various embodiments of the present invention, and also in accordance with certain embodiments of the present invention described herein, components that disable "non-default" channels can conserve significant power, such as the right audio processing component: receive gain 366, receive filter 368, digital-to-analog converter 372, and right headset amplifier 382.

As can be appreciated from the above description, the present invention provides an apparatus and method for reducing power consumption in a mobile unit. It will be apparent from the above description that various techniques can be used to implement the concepts of the present invention without departing from its scope. Furthermore, while the invention has been described with specific reference to certain embodiments, a person of ordinary skill in the art would understand that changes can be made in form and detail without departing from the spirit and the scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. It should be understood that the invention is not limited to the particular embodiments described herein, but is capable of many rearrangements, modifications, and substitutions without departing from the scope of the invention.

Thus, an apparatus and method for reducing power consumption in a mobile unit has been described.

Claims (20)

1. An apparatus for communicating with an audio multiplexer that receives a vocoder input from a vocoder and an audio decoder input from an audio decoder, the apparatus comprising:

a stereo/mono control unit coupled to the codec;

the stereo/mono control unit receiving an audio multiplexer input from an audio multiplexer, the stereo/mono control unit providing a control output to a codec to reduce power consumption within the codec,

wherein the control output disables at least one of the plurality of components within the receive audio processing path of the codec when the audio multiplexer input received by the stereo/mono control unit comprises a speech signal.

2. The apparatus of claim 1, wherein the control output is coupled with a plurality of components within a receive audio processing path of a codec.

3. The apparatus of claim 2, the plurality of components being within a right channel of a receive audio processing path.

4. The apparatus of claim 2, the plurality of components being within a left channel of a receive audio processing path.

5. The apparatus of claim 2, the control output to disable at least one of the plurality of components to reduce power consumption within a receive audio processing path of the codec.

6. The apparatus of claim 2, wherein the plurality of components includes a receive gain, a receive filter, a digital-to-analog converter, a left/right selector, and a headset amplifier.

7. The apparatus of claim 6, the control output to disable at least one of a plurality of components to reduce power consumption within a receive audio processing path of a codec.

8. The apparatus of claim 1, wherein the plurality of components comprise a receive gain, a receive filter, a digital-to-analog converter, a left/right selector, and a headset amplifier.

9. The apparatus of claim 1, wherein the stereo/mono control unit further receives a plug-in detection input from a plug-in detection circuit.

10. The apparatus of claim 9, wherein the plug-in detection circuit receives an I/O input from an I/O socket.

11. A method of processing an audio signal received within an apparatus, the method comprising:

disabling a first channel within the receive audio processing path and enabling a second channel within the receive audio processing path when the audio signal comprises a speech signal; and

when the audio signal comprises a music signal, a first channel within the receive audio processing path is enabled and a second channel within the receive audio processing path is disabled.

12. The method of claim 11, wherein the disabling of the first channel is performed by a stereo/mono control unit.

13. The method of claim 12, wherein the disabling of the first channel is performed by a control output of a stereo/mono control unit disabling at least one of a plurality of components within the first channel.

14. The method of claim 13, wherein the plurality of components includes a receive gain, a receive filter, a digital-to-analog converter, a left/right selector, and a headset amplifier.

15. The method of claim 11, wherein the first channel is a right channel in a receive audio processing path and the second channel is a left channel in the receive audio processing path.

16. The method of claim 11, wherein the first channel is a left channel in a receive audio processing path and the second channel is a right channel in the receive audio processing path.

17. The method of claim 12, wherein the apparatus comprises a vocoder and an audio decoder, wherein the vocoder provides a speech signal to the audio multiplexer and the audio decoder provides a music signal to the audio multiplexer.

18. The method of claim 17, wherein the stereo/mono control unit receives an audio signal from an audio multiplexer.

19. The method of claim 11, further comprising determining whether a stereo output component is coupled to the device.

20. The method of claim 19, further comprising disabling the first channel when the stereo output component is not coupled to the apparatus.