Initial Testing of the Tool - pavhofman/nonlinear-compensation GitHub Wiki

Starting from GUI

  • Starting the whole tool with bin/start.sh script
  • All processes are manageable from UI of the control octave script.
  • The menu allows editing Playback and Capture config files.
  • Playback, Capture, and UI (Ctrl) processes can be restarted via UI menu, as well as corresponding logs can be viewed.
  • Shutting down the whole tool: Control -> Quit All CleanSine Processes will quit the loop in the startup script and cleanly shutdown the tool.

Configuration

Example Config Files

cd ~/work/nonlinear-compensation/conf
cp configPlay.example.conf configPlay.conf
cp configRec.example.conf configRec.conf

Audio Device Selection

  • Playback/Capture -> List Available Devices lists names and IDs of available devices for each side. Only closed/not yet used devices are listed.
  • Copy leading part the device name up to hw:XX alsa ID (which can change at every boot) to the corresponding config file via Playback/Capture -> Edit Config File. The device selection works with substring, please make sure the leading part of the name is unique among all device names listed. Example: 
    ...
ID  9: Name: Infrasonic Quartet: ICE1724 (hw:3,0); API: ALSA; 2 channels
ID 10: Name: Infrasonic Quartet: ICE1724 IEC958 (hw:3,1); API: ALSA; 2 channels
...
    Correct playRecConfig.recDevice or playDevice string for the analog output/input would be 'Infrasonic Quartet: ICE1724 ('.
  • Only the "physical" device name is configured, the other device is left at 'octave_loop' (configured already in .asoundrc).
  • If the tool is started with start.sh, the corresponding-side process will start automatically after proper device is configured in the config file (the script runs a while loop checking all the three processes are running)

Default setup

  • Left channel DAC OUT
  • Left channel ADC IN for analysis/compensation, right channel ADC IN for reference measurements

Changing the channels requires modifying constants PLAY_CH_ID and ANALYSED_CH_ID defined in consts.m.

Starting Manually

Alternative option is starting each process independently:

  • Open a terminal, start the control/UI process:
cd ~/work/nonlinear-compensation/octave/
octave mainCtrl.m

  • The UI screen should start up, with both playback and record panels empty - the control process recieves no data yet.

  • Open another terminal, start the playback-bridge process:

cd ~/work/nonlinear-compensation/octave/
octave mainPlay.m
  • Hint: Shortcut Ctrl+N in the terminal starts a new one with the same working directory
  • You should see the playback status in UI window - either no signal available (REW generator is OFF), or parameters of the signal generated by REW
  • Open another terminal, start the capture-bridge process:
cd ~/work/nonlinear-compensation/octave/
octave mainRec.m
  • You should see the capture status in UI window - either no signal available (soundcard outputs are not connected to inputs - no physical loopback present), or parameters of the signal captured by the soundcard

Updating to the Latest Version

  • Info about current version: About -> View GIT Version
  • Updating: About -> Update to the Latest GIT Version

Signal Generator

The tool has a built-in signal generator, on both playback and capture sides. The generator is used by automated transfer measurement and during split-calibration. However, you can use it at any time:

  • Playback/Capture -> Generate
  • Enter one or two frequencies for the first (left) channel. Note: Levels are absolute (not decibels), so that negative values can be used for generating symmetric signal.
  • If values for second channel are not entered, the values from first channel are used. If you want no signal in one of the channels, enter some frequency and put 0 amplitude.
  • The generator params can be changed in any time.
  • Stopping the generator: Playback/Capture -> Stop Generating

Joint-Sides Calibration

First try the joint-sides compensation. This mode is not suitable for production measurement, but good for testing the setup works correctly.

  • Connect analog loopback
  • Make sure REW generator is running, or generate some signal on playback
  • Run Joint-Sides -> Calibrate Joint-Sides (Single Run)
  • The calibration will start, showing current averaging run.
  • After calibration collects enough runs for averaging, it computes the averaged profile and stores to cal files in directory data/

Joint-Sides Compensation

Joint-sides compensation can be performed on playback OR capture side, using the same profile. Since it's "joint-sides", run only on one side at a time :-)

  • Playback -> Compensate Joint-Sides or Capture -> Compensate Joint-Sides
  • If the corresponding calibration files are found, the code loads them and start compensating. UI shows amplitude levels of each compensated harmonic frequency
  • The distortion lines should basically disappear in REW spectrum (enable averaging (linear, exponential) to zoom into the noise).
  • The red arrows on the plot show calibration levels stored in the calfile, green arrows show current signal levels
  • The compensation distortions are interpolated between the calibrated levels to fit the current signal. For loopback calibration/compensation the levels are identical (unless the generating signal is changed after the calibration).

Checking with Distortion Generator

You can check sensitivity to harmonic distortions with built-in distortion generator.

  • Start the compensation, check in REW the signal is clean
  • Playback/Capture -> Distort
  • Enter the requested distortion levels for each harmonic. Please note: unlike in the generator window, the distortion levels are entered in decibels (e.g. -120)
  • After REW averaging you should see the distortion at required levels and frequencies
  • Stopping the distortion generator: Playback/Capture -> Stop Distorting

Split-Sides Calibration/Compensation

Measuring Transfers of Calibration Paths

  • Joint Sides -> Re-Measure LPF/VD Transfer

Calibrating/Calculating Playback-Side Distortions

  • Playback -> Split-Calibrate/Compensate Playback or pushbutton Split-Calib Playback
  • The calculation requires transfer profiles for every harmonic frequency. If transfers are not measured (or too old data), the task re-measures the transfers first.

Calibrating/Compensating the Remaining Capture-Side Distortions

  • Capture -> Calibrate/Compensate Capture at Current Level/Calibrate/Compensate Capture at Range around Current Level or pushbutton Exact-Calib Capture. The tasks will calibrate/compensate joint-sides if the playback side is not currently compensating.