Last week a patent application on an energy efficient device that provides enhanced copyright protections was published, not surprisingly with Apple, Inc. as the assignee. On Thursday, February 4, 2010, US Patent Application 20100030928 published, titled Media processing method and device. Certainly not the most sexy title possible, but the thrust of the invention is a device that allows the central processing unit (CPU) to “loosely” connect multiple media devices in such a way that the CPU does not need to be in a constantly powered on state. Among other things, this will extend the life of the battery charge for the device, and it also enables the digital music, for example, not to be streamed through the CPU. This in turn provides enhanced protection for digital media, making it more difficult to capture the digital media for later unauthorized distribution.
As the patent application explains, the trend in consumer electronics is to combine multiple functionalities into a single portable electronic device. For example, cell phone and media player functionalities can now be merged into one multimedia device (such is the case with the popular iPhone) with a multitude of capabilities. One advantage of combining features into one device is that it eliminates the need to carry multiples devices, and eliminates the need to own multiple devices, which comes with its own economic cost savings.
In order to obtain the desired multiple functionalities in a single multimedia device a CPU is traditionally introduced. The CPU will typically have direct access to all of the features provided in the device. With this design, most of the data, including copyright protected data in the form of digital music or digital video, passes through the CPU for processing and routing. The drawback of using a CPU as the hub through which processing and routing of digitized material is that the CPU is continually powered up, active and consuming battery power. Another drawback of combining multiple functionalities controlled by a CPU is that the device becomes more functional, which is a benefit for the user but a potentially significant drawback insofar as the creator of original, copyrighted content is concerned. In essence, with increased functionality provided by a CPU the risk of unauthorized copying and distribution of copyright material becomes greater. While encryption of copyrighted material may seem a likely candidate to make copyrighted material less susceptible to illegal copying and distribution, once decrypted the protected media may eventually still become available to the CPU and, therefore, remain vulnerable to illegal copying and distribution.
In the present invention covered by this published patent application there is a multimedia device with an independent audio subsystem that handles all of the decoding, mixing, equalizing and routing of the audio signals, and then sends the output audio directly to peripheral output devices. Because the audio subsystem handles all of the processing of audio data, the CPU is not needed beyond the stage of routing audio data to the audio subsystem. Because the audio processing at step can take place with little or no involvement of the CPU, the CPU is free to carry out other processing tasks or alternatively to enter a low power state which extends the useful battery life of the electronic device.
Additionally, the audio subsystem can be configured so that a digital signal processor (DSP) handles the routing, compression/decompression, equalizing, and mixing of telephone audio data, and also blends other audio samples into telephone audio. In embodiments the audio DSP is configured to switch between various audio processing tasks, with a grain of a few milliseconds, in order to avoid delays that may be unacceptable by regulations and/or undesirable to users of the electronic device. For example, the audio DSP may be configured so that if the audio DSP is processing a music audio when the CPU initiates an incoming telephone call, the audio DSP will quickly switch to the processing of real-time telephone audio in order to avoid a delay in the telephone conversation.
Further embodiments of the invention are directed toward a multimedia device with an independent audio subsystem that is loosely coupled to a central processing unit (CPU.) In other words, rather than having audio components directly coupled to a main bus, the audio components are coupled together separately through an independent audio bus to form an independent audio subsystem. The coupling between the host subsystem and the independent audio subsystem is accomplished through data buffers that allow one way communication of data to or from the host subsystem and the audio subsystem. The audio subsystem is independent in the sense that it does not need to further interact with the CPU to accomplish the playing of audio data sent to it from the CPU. Rather, when the CPU sends audio to the audio subsystem, the audio subsystem handles all of the further processing and routing of the audio. Therefore, the audio subsystem receives encoded data from the CPU as though the audio subsystem were an output device.