The new A²B Bus Monitor Application for the Promira Serial Platform^® provides automotive audio engineers an easy-to-use web interface to non-intrusively monitor Analog Devices' Automotive Audio Bus (A²B).

One of the key benefits is seeing the levels of all upstream and downstream digital audio channels simultaneously. Live audio on the A²B bus can also be streamed through the web interface. This instantaneous feedback can help engineers verify channel alignment to make sure the  audio is right where it should be.

After a capture is stopped, an audio sample can be downloaded as a multi-channel WAV file through the web interface. However, the capture buffer in the A²B Bus Monitor is limited to less than 15 seconds. If more audio data is needed,  the WebSocket interface of the A²B Bus Monitor can be used to stream audio data directly to a disk.

To help developers get started, a sample Python script can be downloaded here. This example package includes the script  audio_capture.py and documentation about how to run it. This script requires Python 3, which can be downloaded for free from the Python website.

The audio_capture.py script captures one or more audio streams to disk as 32-bit signed, mono, little-endian PCM files, one file per channel. When the script is invoked with no arguments, the following information is displayed:

     > python audio_capture.py
     usage: example URL SAMPLE_RATE CH1 CH2 CHn...
     URL must start with ws:// or wss://
     SAMPLE_RATE is the audio sample rate in Hz, e.g. 48000
     CH1... is a list of channels to record as integers

Here is an example of how you would invoke the script and the expected output. Please note that [PROMIRA_IP] should be replaced with the specific IP address of your Promira Serial Platform. Cownstream audio channels are numbered 0 through 13, and upstream audio channels are numbered 32 through 45. In this example, the script is streaming the first upstream audio channel (32) to disk.

     > python audio_capture.py ws://[PROMIRA_IP]/api 44100 32
     Starting capture...
     Audio streaming...
     ch: 32 ts: 13.385327140000001
     audiofile setOffset: 2569982
     ch: 32 ts: 13.48532714 stream: 19200 bytes
     ch: 32 ts: 13.58532714 stream: 19200 bytes
     [...]
     ch: 32 ts: 30.985327140000205 stream: 19200 bytes
     ^C
     Stopping capture...
     Stopping streaming...
     Disconnecting...
     Done.

When the script has finished, the file  raw-audio-ch32.pcm should be located in the directory where the script was run.

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