SD Card Audio Experiments

The WTV020-SD-16P SD card audio module is very critical in terms of the type of SD card use and the kinds of audio files that it can play. So you need to prepare your audio files very carefully as follows:

1 The microSD card must be 2GB in size. Certain SD cards do not work. The SanDisk 2GB microSD cards work well for me.

Format the microSD card with the FAT file system. A quick format is OK. (Do not use FAT32 or any other file system.)
2 The audio file format must be:
  • AD4 format
  • mono (not stereo)
  • Sample rate must be 16000 or less
  • Maximum volume gain must be -12dB or less
3 Below are the steps to prepare your audio files:
  1. Use this online audio editor to prepare the audio file.
    Just drag and drop your mp3 or wav file to the large "Drop a File" icon on the web page.
  2. A new window will open.
  3. From the TwistedWave Online Audio Editor menu,
    select Effects | Amplify...
    Set the Gain to -12 dB. Click Apply
    Back in the main window, make sure that the maximum volume is less than -12 dB. If not, then repeat the Gain adjustment again.
  4. From the TwistedWave Online Audio Editor menu,
    select Effects | Convert Sampling Rate
    Select 16000 Hz sampling rate
    Check Resample audio
    Click Apply
  5. From the TwistedWave Online Audio Editor menu,
    select File | Download
    in the Audio Export window, select
      File format: wave audio
      Compression: none
      Bit depth: 16 bit
    save using filename 0000.wav (You can replace 0000 with any 4-digit number)
4 Convert the wav audio file to AD4 format.
You need to download and use this ad4converter.exe program.
This is a DOS command, so you'll first need to open up a Command Prompt cmd window.
(I assume that you know how to use DOS commands.)
Copy both the ad4converter.exe program and your audio file 0000.wav to the same directory.
Browse to the directory containing both the ad4converter.exe program and the 0000.wav audio file.
Run the ad4converter.exe DOS program at the DOS prompt with the following command:
  C:\> ad4converter -e4 0000.wav

If there are no errors, a file named 0000.AD4 will be created.
5 You can have more than one audio file, so repeat steps 3 and 4 for all your audio files.
6 Copy all the AD4 audio files to the microSD card.
7 In the program, replace the number 0 in the command
  wtv020sd16p.playVoice(0);
with the song number that you want to play.