Originally featured on BroadcastEngineering.com
Audio Precision introduces ‘logic analyzer’ view for digital audio
Audio Precision has released a number of new features for its APx Series audio analyzers relating to the display, analysis and control of metadata in HDMI and IEC60598/AES3 digital audio streams. The full version of APx 2.4 is due to be released later this year.
Errors in metadata can cause real problems in HDMI that users just don't see in S/PDIF. A logic analyzer view shows exactly what's going on over time so users can identify what's causing glitches or other issues. There's no better way to troubleshoot these kinds of problems.
The new APx software release has new features relating to metadata analysis and management: two new metadata monitors and a metadata recorder.
The first of the monitors allows the decoding and display of the entire HDMI audio infoframe, including current N and CTS values, HDCP state, audio layout and A/V mute condition, while the second displays the channel status and bits information embedded in IEC60958/AES3-format audio (S/PDIF, Toslink, AES/EBU). Both the HDMI and IEC60598 audio monitors also display digital audio stream type and sample rate, along with Dolby and DTS parameters including ACMOD/AMODE value, dialog normalization level and bit rate.
The metadata recorder is an easy-to-read, colored display capable of plotting the changing states of multiple metadata fields in real time, like a logic analyzer. Up to 15 fields can be displayed simultaneously, allowing engineers to monitor in detail what happens to metadata information when an HDMI device is hot-plugged, or exactly when and where data glitches occur in a corrupted audio stream. Discrepancies between the indicated metadata and that being received are also automatically identified and flagged (for example, if the input sample rate is 48kHz but the channel status indicates that it should be 44.1kHz). The results of such measurements are invaluable in verifying that a device under testing is behaving in compliance with relevant specifications.