FF7/PSX/Sound/AKAO sequence
Contents
Introduction
AKAO frames are most complicated frames in FF7 sound system. ("AKAO" is frame magic, probably developed by Minoru Akao, Square Enix sound programmer :) )
Frame is similar to MIDI sequence - it's custom tracker format for playing sequence sound, well tuned specially for PSX.
This frames are in all FF7 game modules: Field, Battle, Worldmap and in minigames.
All files with exension *.SND are AKAO.
- MINI/ASERI2.SND - Battle Arena theme
- MINI/SENSUI.SND - used in Submarine minigame
- ENEMY6/OVER2.SND - game over sequence
- ENEMY6/FAN2.SND - battle win "fanfare" sequence
- MOVIE/OVER2.SND - same game over sequence, don't know, why to duplicate data
Other AKAO frames are hard-wired in other files.
AKAO frame structure
Header (size: 16 bytes)
struct AkaoHeader
{
static const uint8_t magic[4]; // "AKAO" C-string aka frame *MAGIC*
uint16_t id; // frame ID, used for playing sequence
uint16_t length; // frame length - sizeof(header)
uint16_t reverb_type; // reverb type (range from 0 to 9)
struct AkaoTimeStamp
{
uint8_t year_bcd; // year (in binary coded decimal)
uint8_t month_bcd; // month (in binary coded decimal, between 0x01 - 0x12)
uint8_t day_bcd; // day (in binary coded decimal, between 0x01 - 0x31)
uint8_t hours_bcd; // hours (in binary coded decimal, between 0x00 - 0x23)
uint8_t minutes_bcd; // minutes (in binary coded decimal, between 0x00 - 0x59)
uint8_t seconds_bcd; // seconds (in binary coded decimal, between 0x00 - 0x59)
} timestamp;
};
Channel info (size: 4 bytes + 2 bytes * <channels count>)
struct AkaoChannelInfo
{
uint32_t mask; // represents bitmask of used channels in this frame
uint32_t start_offsets[num_channels]; // offsets to channel opcode data
};
int num_channels = 0; while (int bit = 0; ((info.mask & 0xFFFFFF) & (1 << bit)) != 0; bit++) num_channels++;
First there is 32-bit number (offset 0x10), which represents bitmask of used channels in this frame.
After this frame, there is <channels count> offsets to channel opcode data counting from current offset. Each offsets is a relative offset based on the address *next to* the offset itself. (This is a general rule for early versions of AKAO to interpret relative offsets.)
Channel Commands [AKAO Opcodes]
Most complicated part.
For every channel in AKAO frame there is set of commands to perform. This is similar to Field opcodes. Here I'll call this sound commands "opcodes". Every opcode has it's own number of arguments (from no-arguments, to 3 arguments).
Example (home-created AKAO frame):
Header
41 4b 41 4f - AKAO string
34 12 - frame ID: 0x1234
16 00 - frame length 0x16 in hex or 22 in decimal
04 00 - reverb type: 4 (large studio)
96 12 18 22 46 28 - unknown data
Channel info
01 00 00 00 - this indicates, that used only one channel
00 00 - offset to first channel opcodes: in our example 0x00 means that next to this offset is opcodes for first channel
Channel commands
e8 a8 66 - sets tempo, parameter 0x66a8
ea 00 50 - sets reverb depth
a8 55 - load sample 0x55 from INSTR.ALL to channel
aa 40 - sets channel volume
c2 - turns on reverb effect
a1 0c - sets volume pan
c8 - sets loop point
66 - 0x66 % 11 = 3 (3 means to take 3rd number from play length table), 0x66 / 11 = 9 (9 means to take pitch[9] from loaded instrument record index)
ca - returns to saved loop point with opcode c8
This example plays Chocobo "Whoo-Hoo" (instrument number 0x55) repeatedly.
Sound Opcode list
| Opcode | Summary | Length | Operands | Note | |
|---|---|---|---|---|---|
| 0xA0 | Finish Channel | 1 | |||
| 0xA1 | Load Instrument | 2 | u8 instrument | ||
| 0xA2 | Overwrite Next Delta-Time Length | 2 | u8 delta_time | ||
| 0xA3 | Channel Master Volume | 2 | u8 volume | ||
| 0xA4 | Pitch Bend Slide | 3 | u8 length, s8 semitones | ||
| 0xA5 | Set Octave | 2 | u8 octave | ||
| 0xA6 | Increase Octave | 1 | |||
| 0xA7 | Decrease Octave | 1 | |||
| 0xA8 | Channel Volume | 2 | u8 volume | ||
| 0xA9 | Channel Volume Slide | 3 | u8 length, u8 volume | ||
| 0xAA | Channel Pan | 2 | u8 pan | 64 is the center | |
| 0xAB | Channel Pan Slide | 3 | u8 length, u8 pan | ||
| 0xAC | Noise Clock Frequency | 2 | u8 clock | ||
| 0xAD | ADSR: Attack Rate | 2 | u8 attack_rate | ||
| 0xAE | ADSR: Decay Rate | 2 | u8 decay_rate | ||
| 0xAF | ADSR: Sustain Level | 2 | u8 sustain_level | ||
| 0xB0 | ADSR: Decay Rate & Sustain Level | 3 | u8 decay_rate, u8 sustain_level | ||
| 0xB1 | ADSR: Sustain Rate | 2 | u8 sustain_rate | ||
| 0xB2 | ADSR: Release Rate | 2 | u8 release_rate | ||
| 0xB3 | Reset ADSR | 1 | |||
| 0xB4 | 4 | ||||
| 0xB5 | 2 | ||||
| 0xB6 | 1 | ||||
| 0xB7 | 2 | ||||
| 0xB8 | 4 | ||||
| 0xB9 | 2 | ||||
| 0xBA | 1 | ||||
| 0xBB | 2 | ||||
| 0xBC | 3 | ||||
| 0xBD | 2 | ||||
| 0xBE | 1 | ||||
| 0xBF | 2 | ||||
| 0xC0 | 2 | ||||
| 0xC1 | 2 | ||||
| 0xC2 | Turn On Reverb | 1 | |||
| 0xC3 | 1 | ||||
| 0xC4 | 1 | ||||
| 0xC5 | 1 | ||||
| 0xC6 | 1 | ||||
| 0xC7 | 1 | ||||
| 0xC8 | Loop Point | 1 | |||
| 0xC9 | 2 | ||||
| 0xCA | Return to Loop Point | 1 | |||
| 0xCB | 1 | ||||
| 0xCC | 1 | ||||
| 0xCD | 1 | ||||
| 0xCE | 1 | ||||
| 0xCF | 1 | ||||
| 0xD0 | 1 | ||||
| 0xD1 | 1 | ||||
| 0xD2 | 1 | ||||
| 0xD3 | 1 | ||||
| 0xD4 | 1 | ||||
| 0xD5 | 1 | ||||
| 0xD6 | 1 | ||||
| 0xD7 | 1 | ||||
| 0xD8 | 2 | ||||
| 0xD9 | 2 | ||||
| 0xDA | 2 | ||||
| 0xDB | 1 | ||||
| 0xDC | 2 | ||||
| 0xDD | 3 | ||||
| 0xDE | 3 | ||||
| 0xDF | 3 | ||||
| 0xE8 | Tempo | 3 | u16 tempo | ||
| 0xE9 | 4 | ||||
| 0xEA | Reverb Depth | 3 | u16 depth | ||
| 0xEB | 4 | ||||
| 0xEC | 3 | ||||
| 0xED | 1 | ||||
| 0xEE | 3 | ||||
| 0xEF | 3 | ||||
| 0xF0 | 4 | ||||
| 0xF1 | 4 | ||||
| 0xF2 | 2 | ||||
| 0xF3 | 1 | ||||
| 0xF4 | 3 | ||||
| 0xF5 | 1 | ||||
| 0xF6 | 2 | ||||
| 0xF7 | 3 | ||||
| 0xF8 | 2 | ||||
| 0xF9 | 1 | ||||
| 0xFA | |||||
| 0xFB | |||||
| 0xFC | 3 | ||||
| 0xFD | 3 | ||||
| 0xFE | 2 | ||||
| 0xFF |
