FishMarket 1.0/FishMarket v1.0.iso/fishies/201-225/disk_203/gurusguide/audio.c

C/C++ Source or Header | 1992-05-06 | 5KB | 187 lines

/************************************************************************
**********                                                     **********
**********            A U D I O   I N T E R R U P T            **********
**********            -----------------------------            **********
**********                                                     **********
**********        Copyright (C) 1988 Sassenrath Research       **********
**********                All Rights Reserved.                 **********
**********                                                     **********
**********    Example from the "Guru's Guide, Meditation #1"   **********
**********                                                     **********
*************************************************************************
**                                                                     **
**                            - NOTICE -                               **
**                                                                     **
**  The "Guru's Guide, Meditation #1" contains detailed information    **
**  about Amiga interrupts as well as a complete discussion of this    **
**  and other examples.  Meditation #1 and all of its examples were    **
**  written by Carl Sassenrath, the architect of Amiga's multitasking  **
**  operating system.  Copies of the "Guru's Guide" may be obtained    **
**  from:                                                              **
**           GURU'S GUIDE, P.O. BOX 1510, UKIAH, CA 95482              **
**                                                                     **
**  Please include a check for $14.95, plus $1.50 shipping ($4.00 if   **
**  outside North America).  CA residents add 6% sales tax.            **
**                                                                     **
**  This example may be used for any purposes, commercial, personal,   **
**  public, and private, so long as ALL of the above text, copyright,  **
**  mailing address, and this notice are retained in their entirety.   **
**                                                                     **
**  THIS EXAMPLE IS PROVIDED WITHOUT WARRANTY OF ANY KIND.             **
**                                                                     **
************************************************************************/

/*
**  IMPORTANT WARNING:
**
**  This example steals the AUD0 interrupt vector.  This action
**  defeats the purpose of the Audio Device - but we wanted to
**  keep the example short and to the point.  We advise you to
**  read the documentation for the Audio Device.
*/

/*
**  COMPILATION NOTE:
**
**  Compiled under MANX AZTEC C 3.6A.  Use the +L compiler option
**  and the "c32" library.  Link with intrsup.o.
*/


#include <exec/exec.h>
#include <hardware/custom.h>
#include <hardware/dmabits.h>
#include <hardware/intbits.h>

#define    SIZE 256    /* wave size */

struct Interrupt *Intr = NULL;
struct Task *ATask = NULL;
long ASignal = -1;

char *WaveForm = NULL;

short RepCount;        /* wave rep counter */
short Part;        /* ADSR envelope count */
short Volume;

/* Attack, decay, sustain, release tables: */
char ADSR[] = { 3, 3, 5,20 }; /* Reps */
char Ramp[] = {20,-5, 0,-2 }; /* Incr */

/* Periods for several "notes" */
short Period[] = { 100,200,300,400,3000,0 };


/* Interrupt Processing Code */
VOID IntrProc()
{
    int_start();

    /* Next ADSR part? */
    if (--RepCount <= 0)
    {
        ++Part;
        RepCount = ADSR[Part];
    }

    /* Finished with note? */
    if (Part > 3)
    {
        Volume = 0;
        DisableIntr(INTB_AUD0);
        Signal(ATask,1 << ASignal);
    }
    else /* Change volume & clip */
    {
        Volume += Ramp[Part];
        if (Volume < 0) Volume = 0;
        else if (Volume > 63) Volume = 63;
    }

    custom.aud[0].ac_vol = Volume;
    ClearIntr(INTB_AUD0);

    int_end();
}


main()
{
    struct AudChannel *ac;
    int n;

    MainInit();

    /* Generate unfiltered noise: */
    for (n = 0; n < SIZE; n++)
        WaveForm[n] = (char)rand();

    AddHandler(INTB_AUD0, Intr);

    /* Turn on audio DMA */
    custom.dmacon = DMAF_SETCLR | DMAF_AUD0 | DMAF_MASTER;

    ac = &custom.aud[0];
    ClearIntr(INTB_AUD0);

    for (n = 0; Period[n] > 0; n++)
    {
        Volume = 0;
        Part = 0;
        RepCount = ADSR[0];
        ac->ac_per = Period[n];
        ac->ac_ptr = (UWORD *)WaveForm;
        ac->ac_len = SIZE/2;
        ac->ac_vol = Volume;

        EnableIntr(INTB_AUD0);

        Wait(1 << ASignal);
    }

    /* Turn off audio DMA */
    custom.dmacon = DMAF_AUD0;

    RemHandler(INTB_AUD0, Intr);

    MainExit(0);
}


MainInit()
{
    extern struct Interrupt *MakeIntr();
    extern long AllocSignal();
    extern struct Task *FindTask();
    extern void *AllocMem();
    extern int Enable_Abort;

    Enable_Abort = 0;    /* prevent a CTRL-C */

    Intr = MakeIntr("audio.example",0,&IntrProc,0);
    if (Intr == NULL) MainExit(201);

    /* Audio DMA needs waveform in chip memory */
    WaveForm = AllocMem(SIZE, MEMF_CHIP | MEMF_CLEAR);
    if (WaveForm == NULL) MainExit(202);

    ASignal = AllocSignal(-1);
    if (ASignal == -1) MainExit(203);

    ATask = FindTask(NULL);
}


MainExit(error)
    int error;
{
    FreeIntr(Intr);

    if (WaveForm != NULL) FreeMem(WaveForm, SIZE);

    if (ASignal != -1) FreeSignal(ASignal);

    exit(error);
}