Manually equipping the memory card of an hörbert 2011 under Linux

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Howto: How to record music and audio plays to the memory card for hörbert 2011 under Linux (you don’t need the hörbert software for this)

Requirements
What you need
You can fill the card yourself with ‘sox’ and simple file commands. You can usually install ‘sox’ with the package manager of your distribution.

The file system

Format of the memory card
The memory card must be formatted in FAT32. This is the format in which our memory cards are delivered. According to the specification, a maximum of 32GB cards can be formatted with FAT32.

Folder structure and files on the card
The root directory of the card must contain folders with the names 0 to 8. These contain your audio files 0.WAV 1.WAV 2.WAV and so on. The file names determine the playback order in the playlist and begin with 0.WAV (decimal number zero).

hoerbert.xml
As long as you always convert the files yourself and copy them to the memory card of hörbert 2011, you do not have to worry about the file hoerbert.xml. This file is only used by the hörbert software for Mac and Windows. If it is not available, the hörbert software can create it itself. Nevertheless, it is better not to delete the file, because even a not up-to-date hoerbert.xml keeps the memory free in case it should be updated sometime.

The audio file format

Converting your audio files
The audio files for hörbert 2011 must be in WAV format with 32 KHz sample rate, 16 bit, mono. With the tool ‘sox’ you can use the following command line for the conversion. Which files your ‘sox’ programme can read depends on the compiled options.

sox --buffer 131072 --multi-threaded --no-glob inputFileName --clobber -r 32000 -b 16 -e signed-integer --no-glob outputFilename.WAV remix - gain -n -1.5 bass +1 loudness -1 pad 0 0 dither

Why not copy directly?

Why can’t you copy mp3 files directly to the memory card for hörbert 2011?
Quite simple: so that you have to change batteries less often. Decoding mp3 files requires more computing power than playing WAV files. mp3 decoder chips sometimes even need more power on their own than hörbert 2011 needs in total. If you don’t have enough space, you can buy a larger memory card for a little money, but then you will need to change batteries less often over the entire period of use.