19.1 Bank Files

Bank files store the audio and control information needed to create audio from sequencer MIDI events. On the Nintendo 64, this information is separately stored in two different files: the bank file and the wave table file.

The Bank (.bnk) file contains control information such as program number to instrument assignment, key mapping, tuning, and envelope descriptions. It is always loaded into the Nintendo 64 DRAM during playback.

The Wavetable (.tbl) file contains ADPCM compressed audio data. Because of the size of the data, it is streamed into DRAM (and then to the RCP) only when it is needed.

The formats for both files are optimized for the Nintendo 64 to be efficiently used with the Sequence Player and the Sound Player. They are not intended to be interchange file formats, and contain no textual information or other data not directly related to playing back audio. Many features commonly found in standard patch and wavetable formats (for example, AIFF files) were sacrificed in favor of smaller files in ROM.

Note: References to objects are stored as offsets in the Bank files, but the alBnkfNew() call converts the offsets to pointers.

19.1.1 ALBankFile

Bank files must begin with an ALBankFile structure. This structure allows the software to locate data for a specific bank.

typedef struct {
        s16     revision;
        s16     bankCount;
        s32     bankArray[1];
} ALBankFile;

19.1.2 ALBank

The ALBank structure specifies the instruments that make up the bank, as well as the default sample rate and percussion instrument. Banks may contain any number of programs.

Note: The percussion field specifies an instrument for the Sequence Player to use as a default MIDI channel 10 (drum channel) instrument.

typedef struct {
        s16   instCount;
         u8   flags;
         u8   pad;
        s32   sampleRate;
        s32   percussion;
        s32   instArray[1];
} ALBank;

19.1.3 ALInstrument

The ALInstrument structure contains pronunciation information.

typedef struct {
        u8      volume;
        u8      pan;
        u8      priority;
        u8      flags;
        u8      tremType;
        u8      tremRate;
        u8      tremDepth;
        u8      tremDelay;
        u8      vibType;
        u8      vibRate;
        u8      vibDepth;
        u8      vibDelay;
        s16     bendRange;
        s16     soundCount;
        s32     soundArray[1];
} ALInstrument;

19.1.4 ALSound

The ALSound structure contains information about the individual sounds that make up an instrument.

typedef struct Sound_s {
        s32     envelope;
        s32     keyMap;
        s32     wavetable;
        u8      samplePan;
        u8      sampleVolume;
        u8      flags;
} ALSound;

19.1.5 ALEnvelope

The ALEnvelope structure describes the attack-decay-sustain-release (ADSR) envelope for a sound.

Note: Release volume is assumed to be 0.

typedef struct {
        s32     attackTime;
        s32     decayTime;
        s32     releaseTime;
        s16     attackVolume;
        s16     decayVolume;
} ALEnvelope;

19.1.6 ALKeyMap

The ALKeyMap describes how the sound is mapped to the keyboard. It allows the sequencer to determine at what pitch to play a sound, given its MIDI key number and note on velocity.

Note: C4 is considered to be middle C (MIDI note number 60). Bank files may not contain keymaps that have overlapping key or velocity ranges.

typedef struct {
        u8      velocityMin;
        u8      velocityMax;
        u8      keyMin;
        u8      keyMax;
        u8      keyBase;
        u8      detune;
} ALKeyMap;

19.1.7 ALWavetable

The ALWavetable structure describes the sample data to be played for the given sound. It is described in detail below, along with the structures it contains.

enum    {AL_ADPCM_WAVE = 0, AL_RAW16_WAVE};

typedef struct {
        s32             order;
        s32             npredictors;
        s16             book[1];        /* Must be 8-byte aligned */
}ALADPCMBook;

typedef struct {
        u32             start;
        u32             end;
        u32             count;
        ADPCM_STATE     state;
}ALADPCMloop;

typedef struct{
        u32             start;
        u32             end;
        u32             count;
}ALRawLoop;

typedef struct{
        ALADPCMloop     *loop;
        ALADPCMBook     *book;
}ALADPCMWaveInfo;

typedef struct{
        ALRawLoop       *loop;
}ALRAWWaveInfo;

typedef struct{
        s32             base;
        s32             len;
        u8              type;
        u8              flags;
        union{
                        ALADPCMWaveInfo adpcmWave;
                        ALRAWWaveInfo           rawWave;
        }waveInfo;
}ALWaveTable;

Table 19-8 ALADPCMWaveInfo Structure

Field	Description
loop	Offset or pointer to the ADPCM-specific loop structure.
book	Offset or pointer to the ADPCM-specific code book.

Table 19-9 ALRawWaveInfo Structure

Field	Description
loop	Offset or pointer to the raw sound loop structure.

Table 19-10 ALADPCMLoop Structure

Field	Description
start	Sample offset of the loop start point.
end	Sample offset of the loop end point
count	Number of times the wavetable is to loop. A value of -1 specifies an infinite loop.
state	ADPCM decoder state information.

Table 19-11 ALADPCMBook Structure

Field	Description
order	Order of the ADPCM predictor.
npnredictors	Number of ADPCM predictors.
book	Array of code book data.

Table 19-12 ALRawLoop Structure

Field	Description
start	Sample offset of loop start point.
end	Sample offset of loop end point.
count	Number of times the wavetable is to loop. A value of -1 specifies an infinite loop.