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CSR shows apt-X LIve at AES

Andrew Low
CSR shows apt-X LIve at AES

CSR has announced it will demonstrate a new DSP-based evaluation platform for its apt-X Live CODEC.

Apt-X Live was designed to help overcome the spectrum efficiency and audio quality challenges involved in digital wireless microphone and in-ear monitoring system design. CSR’s evaluation platform demonstrates the optimised audio bandwidth, dynamic range, and audio delay performance available to digital wireless microphone reference designs that leverage apt-X Live low-latency CODEC technology.

Digital wireless systems have been brought to the forefront as Governments in the UK and abroad continue to sell off the frequency bands used for wireless audio systems to Broadband providers. One of the benefits of digital systems is their potential to offer more efficient use of the radio frequency spectrum for a given audio quality. Key to microphone designs achieving this spectrum efficiency is the use of low-latency audio compression technology as an essential sub-system in the signal processing chain.

CSR’s apt-X Live CODEC is aimed for the requirements of digital wireless microphones. The patented architecture is said to provide generous audio data rate reduction and an enhanced degree of error tolerance, all with extremely low latency.

This apt-X Live evaluation platform comprises separate digital radio transmitter and receiver modules and is designed to demonstrate how low-latency audio CODEC subsystem within a typical digital wireless microphone system can be successfully implemented using CSR’s apt-X Live.

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In operation, the programmable DSP-based digital radio transmitter module takes a mono channel audio input (16-bit resolution, sampled at 48kHz) and compresses this in real-time using the apt-X Live algorithm running at 2.5 bits per PCM sample to produce a compressed bitstream at 120kbits/sec. This bitstream is digitally modulated using FSK onto an 868MHz RF carrier, and transmitted over the air to a similar DSP-based receiver module that demodulates the bitstream, and decompresses the data to reproduce the original PCM audio signal.

The apt-X Live audio CODEC can deliver a single channel of 24bit, 48kHz audio in 120kbps with a codec latency of less than 1.9ms.The framework of apt-X Live audio coding will provide a higher resilience to random bit errors. Additional techniques employed within apt-X Live also will reduce the significance of these errors and the magnitude of the audible effect on certain signals.

Chris Havell, director of audio marketing, CSR commented: “Our evaluation platform helps to prove the CSR low-latency apt-X Live audio CODEC’s ability to satisfy key design criteria for deployment in digital wireless microphone systems. We expect audio system designers will be impressed with the audio bandwidth, dynamic range and end-to-end audio latency of this apt-X Live demonstrator. These are the fundamental parameters which determine overall performance of digital wireless microphone systems.”

Tags: 129th aes convention, csr shows apt-x live, digital wireless

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