Nintendo 3DS Sound

Nintendo 3DS Sound is the music playing and audio recording application that is included with all retail consoles.

It loads audio files from the sd card. It supports MP3 and AAC encoded audio files and supports m3u playlists.

Playlist file format

The application allows for user created playlists. They are stored on the SD card.

Offset	Size	Description
0x00	0x04	Magic bytes, 'O', 'V', 'A', 'F' or "FAVO" endian corrected.
0x04	0x04	Always integer with value 16
0x08	0x04	File size (0x26730)
0x0C	0x04	Zero Padding
0x10	0x02	checksum (songs?)
0x12	0x02	Icon ID (0-44) if id==-1 then loads custom icon from end of playlist?
0x14	0x02	Song file count
0x16	0x02	Number of possible songs (usually 0x12C/300)
0x18	0x04	some kind of timestamp, for encryption (dosn't change when editing)
0x1A	0x01	checksum (icon?, header?) (dosn't change when editing)
0x1B	0x01	checksum (name?) (dosn't change when editing)
0x1C	0x04	always(?) integer with value 6
0x20	0x100 (avaiable 0x40)	Playlist name stored in UTF-16
0x120+(n*0x20C) => n<300	692 (0x20C per song)	File name stored in UTF-16. Repeats for the rest of the file.
0x2672F	-	End

Sample reader

This is a basic example of how to read a 3DS playlist. I know that this works on my specific system; on any other system, it's liable to fail. I'm not responsible if you hurt yourself.

/* This is free and unencumbered software released into the public domain.
/* Anyone is free to copy, modify, publish, use, compile, sell, or
/* distribute this software, either in source code form or as a compiled
/* binary, for any purpose, commercial or non-commercial, and by any
/* means.

/* In jurisdictions that recognize copyright laws, the author or authors
/* of this software dedicate any and all copyright interest in the
/* software to the public domain. We make this dedication for the benefit
/* of the public at large and to the detriment of our heirs and
/* successors. We intend this dedication to be an overt act of
/* relinquishment in perpetuity of all present and future rights to this
/* software under copyright law.
/* 
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
/* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
/* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
/* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
/* OTHER DEALINGS IN THE SOFTWARE.
/*
/* For more information, please refer to <http://unlicense.org/> */

#include <stdio.h>
#include <stdint.h>

uint8_t buf[0x26730];
uint16_t checksum, icon, songCount;
uint32_t timestamp;
uint8_t playlistName[0x100];
uint8_t songName[0x20C][299];

void readUtf16AsAscii(uint8_t *input, uint8_t *output, uint16_t length, uint32_t offset) {
	uint16_t j=0;
	for (j=0; j<length; j++) {
		output[j] = input[(j*2)+offset];
	}
}

int main(int argc, char* argv[]) {
	uint16_t t=0;
	FILE *playlistFile;

	if (argc != 2) {
		printf("Usage: %s FILE\n", argv[0]);
		exit(1);
	}

	if ((playlistFile = fopen(argv[1], "rb")) == NULL) {
		printf("Could not open %s.\n", argv[1]);
		exit(1);
	}

	if (fread(buf, 1, 0x26730, playlistFile) != 0x26730) {
		printf("Could not 0x26730 bytes from %s.\n", argv[1]);
		exit(1);
	}

	if (!((buf[0] = 'O') && (buf[1] = 'V') && (buf[2] = 'F') && (buf[3] = 'A'))) {
		printf("%s is not a 3DS playlist file.\n", argv[1]);
		exit(1);
	}

	checksum  = (buf[0x11] << 8)  | buf[0x10];
	icon      = (buf[0x13] << 8)  | buf[0x12];
	songCount = (buf[0x15] << 8)  | buf[0x14];
	timestamp = (buf[0x17] << 24) | (buf[0x16] << 16) | (buf[0x19] << 8) | buf[0x18];
	readUtf16AsAscii(buf, playlistName, 0x100, 0x20);
	for (t=0; t<songCount; t++) readUtf16AsAscii(buf, songName[t], 0x20C, (0x120+(t*0x20C)));

	printf("Checksum:\t%04X\nIcon ID:\t%04X\nSong Count:\t%04X\nTimestamp:\t%08X\nPlaylist Name:\t\"%s\"\n",
	checksum, icon, songCount, timestamp, playlistName);

	for (t=0; t<songCount; t++) printf("Name of song %03i: %s\n", t, songName[t]);
}