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Saturday, 11. June 2005
Juicebox Audio

Ok, Make made me do it. I bought the Juicebox ($13 at Target) and the MP3/Photo adapter (ouch $23 at a different Target). Took a while to get the audio in the right format. It won't play anything unless the sample rate is 44,100 Hz (says 44 but 44,1 works). I've found a lot of podcasts etc at 22050 Hz and that just doesn't work. The bitrate (compression) needs to be 128kps or less. And it has to be in stereo. This is a very limited player, but let's face it, a limited hardware platform as well. Oh yeah, gotta be MP3. (Sample rates are Hz, not kHz --ed)

The .mp3 files work fine in the root directory of the SD card, I haven't tried putting them in subdirectories. So for audio files you don't need the juicebox software. As long as the format is OK you can just copy them to the card.

Here's how I got good audio files on Linux:

  1. Resample the file using sox: sox input.wav -r 44100 -c 2 output.wav
  2. Encode to MP3 using lame: lame -b 96 output.wav output.mp3
  3. Copy output.mp3 to the SD card
I found that lame will keep the 44100 sample rate if you select a bitrate of 96 or 128. I don't know if it will upconvert files from a slower sample rate.

It took a bit of work but now I can listen to my Morse Code practice files as I drive. Isn't that what it's all about?

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Biography

Randall Bohn lives in Orem, Utah, USA. He works as a Software Quality Engineer. He is a big fan of the AVR line of microcontrollers. He has been in the computer industry since 1989. Randall is married and has three children.

rsbohn can be reached via gmail.com.


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