High resolution audio in smartphones, IoT applications
More than ever, we’re using smartphones and home IoT entertainment systems to consume audio. As capabilities of these devices expands, so has demand for high resolution audio for music streaming subscriptions, and companies are now exploring how to bring high definition audio to these resource-constrained mobile and Internet of Things (IoT) devices.
The smartphone and associated music download sites have become one of the primary ways we consume music. MP3 compressed audio has been the common format due to the balance of audio quality and compression. However, as smartphones advance in memory and sophistication, there has been a shift toward the demand for high resolution audio in these environments. Likewise, for in-home IoT applications, audio playback is a fundamental capability and lossless audio streaming is particularly important.
Nigel Burgess, Principal Product Line Manager with Cirrus Logic, talked with me about the challenges and opportunities for high resolution audio in the mobile and IoT markets. According to Burgess, Cirrus Logic’s primary objective is to bring high end studio audio quality to the phone without sacrificing battery life.
“Our objective at Cirrus Logic has always been to provide hardware and software solutions across the entire audio and voice processing chain and create a transparent audio path”. One of the primary issues with high resolution audio involves clock jitter affecting the audio signal, especially within the smartphone and embedded environments,” said Burgess. “The Cirrus Logic 512 single-bit digital analog converter (DAC) architecture is designed to reduce jitter that can cause audio performance degradation while filtering out unwanted noise to deliver clear audio. Digital audio passed through each of the pipelined 512 single cell DACs provides sequential filtering out of unwanted audio.
“Increased storage capacity and higher delivery bandwidths can now support high resolution audio. It’s our job to make sure the hardware isn’t the limiting factor.”
In response to the high resolution audio demand, Cirrus Logic has introduced two new product streams: CS43130 SmartHIFI, which combines powerful digital signal processing and high performance without excessive battery drain, and CS4399 MasterHIF, which provides highest standard audio converters but without the DSP programming.
There are a number if interesting technical features of the CS43130 that bear mentioning:
- Non-oversampling mode recreates the “old school” sound from non-oversampling amplifiers. There is a resurgence in popularity of vinyl records and valve amps that produce a unique sound some audiophiles prefer. The original CD players used non-oversampling DACs and over time that sound has been lost due to modern digital oversampling techniques.
- Playback up to 32-bit and 384 kHz sample rate provides high quality audio playback for stored and streaming content.
- 130 dB dynamic range allows for quietest to loudest audio without reduction in quality.
- Dedicated processing for DSD audio up to DSD256.
- Advanced Hi-Fi filters help the system designed achieve the “right sound” by avoiding things like “pre-ringing” – for example, the waveform sound of a ringing cymbal may start before the cymbal is struck in the audio mastering. These filters can cancel these things out for more true audio.
- Up to 4X lower power. This is perhaps the biggest factor enabling high resolution audio within the smartphone environment. The parts consume up to four times less power than competing parts.
Movement back to over-the-ear headphones
Another interesting phenomenon is the movement toward larger over-the-ear headphones. It’s important that smartphones and embedded IoT devices drive these headphones properly.
Software development kit
Cirrus Logic has a development kit called WISCE that provides tools and utilities for a range of Cirrus Logic devices. The kit allows users to change register settings easily and make a smooth migration from prototype boards to production. There are also Linux drivers that plug into the Android solution for faster development and integration.