Setting Bluetooth level via AVRCP
Introduction
This sequence sets a Bluetooth device to hit a target pressure level by adjusting the level via SoundCheck commands to the Bluetooth device. In some applications when testing via Bluetooth, such as automotive, it is inconvenient to adjust the Bluetooth level manually. This sequence uses the Audio/Video Remote Control Profile (AVRCP) raw level command connected to a device via A2DP to change the output signal level in an automated sequence until the target is met.
To utilize this, a BQC-4149 or a BTC-4149 must be used to connect to a Bluetooth device that supports AVRCP level control. The sequence will first prompt if you would like to make a new Bluetooth connection. The user is then prompted to select the target level in dBSPL on the output of their device.
Once connected, the current AVRCP level is read from the device, and a measurement is made with a fully saturated 20Hz – 20kHz digital pink noise signal. The current test level is measured. A loop will run measuring +/- 6dB, changing the raw AVRCP level by 20. Once this is met, another loop will run +/-3dB changing the AVRCP level by 3, and finally a loop will run with +/-1dB limits adjusting the AVRCP level by 1 until the target level is met.
The display shows the current measured level, the target level, and the difference as well as the AVRCP level.
Software Requirements
- SoundCheck Plus version 23 or later
- Module 2042 – Python Custom Step
- Windows Operating System
Hardware Requirements
- BQC-4149 or BTC-4149
- Listen SCM4 Reference Mic p/n4012 (or equivalent)
- Listen AudioConnect 2 p//n 4047 audio interface/microphone power supply (or equivalent)
Setup & Calibration
- Before opening the sequence, copy over the attached “Absolute Volume (Tkinter).py” file to “C:\SoundCheck\System\Custom Py”. See the SoundCheck manual Section 29.13 for more information on how to configure SoundCheck for Python Custom Steps.
- The appropriate Portland Tool & Die control software must be installed and added to PATH. The latest Firmware is also recommended to make sure the AVRCP feature is supported on your device. The InstrumentUpdate (for Firmware) and control software (WindowsSetup) can be downloaded from the following links:
- Note: This sequence is configured for use with a BQC-4149. If using a BTC-4149, the message steps to connect to the BQC must be switched over to BTC.
- Steps 3-6 must change the device ID from BQC1 > BTC1
- Steps 8, 19, 29, and 41 must be changed from BQC4149 > BTC4149 in the device dropdown
- Calibrate your reference microphone as instructed in the SoundCheck user manual
The sequence is ready for use.
System Diagram
Further Sequence Development
This sequence has been designed for simplicity and has been written for a stereo channel system, to be accessible to 100% of SoundCheck users. Ways in which you could modify or further develop the sequence include:
- The current sequence uses the raw AVRCP level with a range from 0-127. Instead, the absolute AVRCP can be used that has a range of 0-15.
- There are 3 loops in the sequence:
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- +/-6dB limits that adjust AVRCP by 20
- +/-3dB limits that adjust AVRCP by 3
- +/-1dB limits that adjust AVRCP by 1
- These might not be appropriate for your device. Both the limit range and the level changed can be adjusted for your specific device.
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- A single reference microphone is used in this example. Instead, a microphone array or ear simulators on a head and torso simulator could be used.
Download Setting Bluetooth level via AVRCP Sequence (zip file)
Download Setting Bluetooth level via AVRCP Sequence documentation (PDF)
