03.08.2009 08:50 AM
Originally featured on BroadcastEngineering.com
Audio Precision updates APx analyzers

Audio Precision has introduced an update for its APx Series of audio analyzers that allows measurement of the digital error rate of a device handling lossy encoded digital audio in formats such as Dolby and DTS. The new Version 2.3 update ensures proper testing of any device designed to pass audio over HDMI and other digital protocols. APx Series owners can download this update at no charge.

Version 2.3 contains project files for Dolby and DTS confidence testing, compliant with the certification manuals of both manufacturers. It also includes support for the APx Digital Serial I/P option — recording input signals to disc, upgraded level and frequency sweeps, easy measurement microphone calibration and navigation enhancements.

Every device that passes digital audio strives to be bit accurate; however, some devices may unintentionally truncate data, introduce dither, scale the signal or convert the sample rate. These errors may be hard to detect. Most audio analyzers can already measure in “bit stream mode” to ascertain that digital audio is passed through a device without corruption. However, there has been no way to test lossy encoded audio formats such as Dolby and DTS. Audio Precision’s new technique allows both lossless and lossy streams to be tested.

APx calculates the digital error rate by measuring a waveform on a sample-by-sample basis. The algorithm used allows the instrument to test closed-loop digital devices (such as routers and switchers) as well as playback devices like DVD players. Version 2.3 APx analyzers can generate the test signal from any digital output, including SPDIF, Toslink, HDMI and AP’s new Digital Serial I/O interface. In addition, the test signal is provided as WAV, AC3 (Dolby 5.1), DTS (DTS-encoded 5.1 audio) and DTSHD (DTS-HD Master Audio) files.

The digital error measurement can also be used to test bit-for-bit accuracy over time (to more than 10,000 minutes). Available views of the data include average error rate, instantaneous error rate, total errors and cumulative errors over time.

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