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Running the Audio Loop-back Test (Windows Embedded CE 6.0)

  • Article

1/6/2010

Applies to Windows Embedded CE 6.0 R2

To run the Audio Loop-back test

  1. Connect the analog-line level-audio-output on the device being tested to the analog microphone audio-input using a loop-back cable.

  2. Upload the sample files distributed with this test to the device being tested using the Windows Embedded CE Remote File Viewer.

    1. Open Platform Builder.
    2. From the menu bar, click Target.
    3. From the Target menu select Remote Tools.
    4. From the Remote Tools menu, select File Viewer.

  3. Verify that LoopBackTest.exe is available in your release directory on the device being tested.

  4. From the Windows Embedded CE Command Prompt type ***loopbacktest.exe -i ***InputFilePath ***-o *OutputFilePath andpress ENTER. Following is an example:

    loopbacktest.exe -i \sinewave_8000.wav -o\mic_8000.wav

  5. The test will play this sample file on a loop for approximately one hour. It will automatically stop if the playback and capture audio devices drift by one or more buffer lengths.

Note

There are two sample files provided with this test:

  • Sinewave_8000.wav, a 16-bit. Mono, 8000Hz, and 30-seconds in duration
  • Sinewave_16000.wav, a 16-bit. Mono, 16000Hz, and 15-seconds in duration
  1. If the test succeeds, it will create an output file at the specified location with the specified name.
  2. Download the output file from the device being tested to the PC using the Windows Embedded CE Remote File Viewer.

To validate the Audio Loop-back test

  1. Open the Audacity sound editor.

  2. From the Audacity user interface, open the output file generated by the loop-back test. To do this, select File then Open.

  3. Zoom-in at the start of the waveform until you get clarity of 1ms, as shown in the following illustration:

  4. Write down the reading of the cursor position at the very start of the first sample of the audio file, using the cursor field in the status part at the bottom of the window. For instance, in the example above, this reading is 0.201313 seconds.

  5. Subtract 0.200000 from the reading you obtained in Step 4 to get the input+output delay in seconds. Again, using the above screen shot as an example, these values are 0.201313 – 0.200000=0.001313 seconds = 13ms.

  6. To pass this test, the input+output value determined in Step 5 must be less than 20ms.

See Also

Other Resources

Audio Loop-back Test