Audio-file-format.md

SD card structure

Every box contains a SD card which is used to store the tonies audio data.

downloaded audio files

The downloaded audio files for tonies are stored on the SD card in a directory for every tonie.

Directories are named by the last 4 bytes of the tonie ISO15693 UID in hex format, e.g. \DEADBEEF. Within that folder there are files in the format 000000XX where XX is a value coded in hexadecimal.

predefined files

Upon initalization the box extracts the content of the flash-internal sfx.bin into two directories with several audio files:

00000000\000000*
00000001\000000*

Audio file format

In general the audio files are just OGG files with some custom header

So the files are structured like this:

<file>   ::= <header> <audio_data>
<header> ::= <header_len> <header_data>

where:
<header_len>  length of <header_data> in big endian uint32, usually 0x00000FFC
<header_data> protobuf coded info fields like SHA1 hash, audio length, etc
<audio_data>  Ogg audio file

Header format

The file header is coded using protobuf and contains these fields:

1. [string]   Audio data SHA-1 hash
2. [variant]  Audio data length in bytes
3. [variant]  Audio-ID of OGG audio file
4. [string]   Ogg page numbers for Chapters
5. [string]   fill bytes „00“ up to <header_len>

To decode the protobuf content, you can use the online decoder at https://protogen.marcgravell.com/decode