format.txt

VOS file format for VOS
=======================

All VOS-related data structures are in little-endian format.

Strings are encoded as:

struct string {
  u8 len;
  char val[len];
};

File structure:
(from beyer85.vos)
0x00: "\x03\x00\x00\x00"
0x04: Segment table:

struct seg {
  u32 offset; /* Offset of the segment in the file */
  char name[16]; /* "inf", "mid", "EOF" */
} segs[variable]; /* The last segment is "EOF" */

The "inf" segment:

Before the inf_header, there can be an optional "VOS1" header:
struct vos1_header {
  char magic[4]; /* "VOS1" */
  u16 version; /* Usually 1 */
  char dummy[64]; /* Usually all zeros */
  string str1;
};

struct inf_header {
  string title; /* Song title */
  string artist; /* Artist of the original song */
  string comment; /* Unknown; in beyer** it is "Step xx" where xx is the difficulty level,
                     but it can also be empty */
  string vos_author; /* Author of the VOS */
  u8 song_type; /* Probably things like "Classical" or "NewAge" */
  u8 extended_type;
  u32 length; /* The unit is approx. 1/974 sec (1024us?) */
  u8 level; /* The shown level minus 1 */
  char dummy[1023]; /* Seems to be zeroed out */
};

After the "inf" header, there is a list of note_arrays.  The last note array just collects
the user-played notes in the other note arrays.

struct note_array {
  u32 type; /* Instrument? */
  u32 nnote; /* Number of notes */
  char dummy2[14]; /* Seems to be always zero */
  note notes[nnote];
}

struct note {
  u32 time;
  u32 len; /* Length of the note */
  u8 cmd, note_num, vol; /* The MIDI key-down command */
  u16 mode; /* Bit 0-3: color (?); 4-6: corresponding key (do,re,mi,fa,so,la,ti);
               Bit 7: set for notes played by the user;
	       Bit 8: set for long notes. */
  char unknown2[2]; /* what?  The first byte can be 0x80 or 0xB0 or 0xD0, ...  Is it the length? */
};

The "mid" segment:
An ordinary MIDI file, but seems to contain initialization stuff only (please investigate further).


VOS file format for CAN
=======================
0x00: "\x02\x00\x00\x00"
What follows is a number of subfiles, terminated by EOF:

struct subfile {
  u32 name_len;
  char name[name_len];
  u32 len;
  u8 data[len];
}

There are usually two subfiles: Vosctemp.trk and VOSCTEMP.mid.  The mid file is the same as the
contents in the "mid" segment above.  The trk file format is described below.

Strings in the trk file are encoded as:

struct string2 {
  u16 len;
  char val[len];
}

The trk file format is as follows:

struct vos022 {
  char magic[4]; /* "VOS0" */
  u16 version; /* "22" */
  string2 title;
  string2 artist;
  string2 comment;
  string2 vos_author;
  string2 str;
  u8 unknown1[11];
  u32 length_tt; /* Length in tempo-based units */
  u32 length; /* Length in real time, in the same units as above */
  char dummy[1024]; /* The first six bytes are sometimes non-zero */
  u32 narr; /* Number of note arrays */
  u32 unknown4; /* Usually 1.  Number of user_arrays? */
  struct {
    u8 a; /* 0x04 */
    u32 type;  /* Instrument */
  } note_arr_info[narr];
  u8 unknown6; /* zero */
  u8 level;
  string2 unknown7;
  u32 unknown8; /* zero */
  struct {
    u32 nnote;
    struct {
      u8 xxx; /* zero */
      u32 time;
      u8 note_num;
      u8 track;
      u8 vol;
      u8 is_user; /* boolean flags */
      u8 xxx; /* one */
      u8 is_long;
      u32 len;
      u8 xxx; /* usually 0xff when is_user is false and 0x00 otherwise; is_bgm?*/
    } notes[nnote];
  } note_arrs[narr];
  u32 ? /* 0 */
  u32 nunote;
  struct {
    u8 arr_idx;
    u32 idx;
    u8 key;
  } unotes[nunote];
  u32 ? /* 0; sometimes it is non-zero and I don't know then how to parse it */
  u32 nlyric;
  struct {
    u32 time; /* in tt */
    string2 lyric;
  } lyrics[nlyric];
}