Question

A person wishes to record audio and save it to memory with an ARM-based CPU architecture. Assuming the audio data is uncompressed, and saved to a hard disk, write a description of what components would be needed to create an audio recorder. Describe how you would perform quantization, and how you would interface the disk controller using a bus mastering scheme.

Answer 1

First, you need the right processing power and efficiency for your application. The Arm Cortex family of processors provides a standard architecture to address the broad performance spectrum and cost range required by these diverse product markets. The Arm Cortex family includes processors based on three distinct profiles:

• The Cortex-A processor family for sophisticated, high-end applications running mainly complex operating systems
• The Cortex-R processor family for high-performance hard real-time systems
• The Cortex-M processor family optimized for low-power, deterministic, cost-sensitive microcontroller applications

The Arm Cortex-M processor family is particularly suited for a wide range of applications that demand high performance with a low computational footprint, such as voice and audio-based devices. In particular, the Cortex-M4, Cortex-M7, Cortex-M33 and Cortex-M35P processors offer digital signal processing (DSP) extensions (to the Thumb instruction set) and an optional floating-point unit (FPU), combining DSP and high-performance generic code processing all-in-one. They are specifically designed to help improve the performance of numerical algorithms and provide the opportunity to perform signal processing operations directly on the CPU – simplifying programming, reducing power and decreasing bill-of-material (BoM) costs.

The ideal preprocessing technologies operate with low MIPS and memory to produce natural sounding intelligible voice on the other end of the call or improve performance of the Automatic Speech Recognition “ASR” engine.

Hallmarks of best-in-class preprocessing technology include the following:

• Fast adaptation to changes in ambient noise level
• Built-in wind noise reduction
• Echo-free, full-duplex, communication

The following Alango software products have been ported and optimized for Cortex-M4 and Cortex-M7 processors:

• Voice Communication Package “VCP” - human-human communication - a universal software package of digital signal processing technologies for voice applications enabling high quality, full duplex, and noise free communication from various environments.
• Voice Enhancement Package “VEP” - human-machine communication - a suite of real-time software DSP technologies designed for improving speech recognition performance in voice-controlled multimedia devices.
• Voice Activity Detector “VAD” - for reliably detecting speech in an acoustic signal
• Sound Reinforcement Package “SRP” - a set of DSP software technologies enabling sound reinforcement in real time PA and In-Car Communication (ICC) systems.
• Sound Effects Normalization “SEN”: Accentuates speech dialog from aggressive special effects in television and streamed content
• MuRefiner audio enhancement allows the user to alleviate the drawbacks of her or his device or listening environment and enjoy the audio content to the maximal possible extent.