mixdrv.c

这个是延伸mame的在wince平台下的游戏模拟器的代码

		}
		else {
		    lpVoice->bControl |= VOICE_STOP;
		    break;
		}
	    }
	}

	/* check for overflow and clip if necessary */
	nSize = nCount;
	if (lpVoice->bControl & VOICE_REVERSE) {
	    if (nSize * lpVoice->dwFrequency >
		lpVoice->dwAccum - lpVoice->dwLoopStart)
		nSize = (lpVoice->dwAccum - lpVoice->dwLoopStart +
			 lpVoice->dwFrequency) / lpVoice->dwFrequency;
	}
	else {
	    if (nSize * lpVoice->dwFrequency >
		lpVoice->dwLoopEnd - lpVoice->dwAccum)
		nSize = (lpVoice->dwLoopEnd - lpVoice->dwAccum +
			 lpVoice->dwFrequency) / lpVoice->dwFrequency;
	}

	if (lpVoice->bControl & VOICE_REVERSE)
	    lpVoice->dwFrequency = -lpVoice->dwFrequency;

	/* mixes chunk of data in a burst mode */
	if (lpVoice->bControl & VOICE_16BITS) {
	    Synth.lpfnMixAudioProc[1] (lpBuffer, nSize, lpVoice);
	}
	else {
	    Synth.lpfnMixAudioProc[0] (lpBuffer, nSize, lpVoice);
	}

	if (lpVoice->bControl & VOICE_REVERSE)
	    lpVoice->dwFrequency = -lpVoice->dwFrequency;

	/* update mixing buffer address and counter */
	lpBuffer += nSize;
	if (Synth.wFormat & AUDIO_FORMAT_STEREO)
	    lpBuffer += nSize;
	nCount -= nSize;
    }
}

static VOID MixAudioVoices(LPLONG lpBuffer, UINT nCount)
{
    UINT nVoice, nSize;

    while (nCount > 0) {
	nSize = nCount;
	if (Synth.lpfnAudioTimer != NULL) {
	    nSize = (Synth.dwTimerRate - Synth.dwTimerAccum + 64L) & ~63L;
	    if (nSize > nCount)
		nSize = nCount;
	    if ((Synth.dwTimerAccum += nSize) >= Synth.dwTimerRate) {
		Synth.dwTimerAccum -= Synth.dwTimerRate;
		Synth.lpfnAudioTimer();
	    }
	}
	for (nVoice = 0; nVoice < Synth.nVoices; nVoice++) {
	    MixAudioData(lpBuffer, nSize, &Synth.aVoices[nVoice]);
	}
	lpBuffer += nSize;
	nCount -= nSize;
    }
}


/*
 * High level waveform synthesizer interface
 */
static UINT AIAPI GetAudioCaps(LPAUDIOCAPS lpCaps)
{
    memset(lpCaps, 0, sizeof(AUDIOCAPS));
    return AUDIO_ERROR_NOTSUPPORTED;
}

static UINT AIAPI PingAudio(VOID)
{
    return AUDIO_ERROR_NOTSUPPORTED;
}

static UINT AIAPI OpenAudio(LPAUDIOINFO lpInfo)
{
    memset(&Synth, 0, sizeof(Synth));
    Synth.wFormat = lpInfo->wFormat;
    Synth.nSampleRate = lpInfo->nSampleRate;
    if (Synth.wFormat & AUDIO_FORMAT_FILTER) {
	Synth.lpfnMixAudioProc[0] = (Synth.wFormat & AUDIO_FORMAT_STEREO) ?
	    MixAudioData08SI : MixAudioData08MI;
	Synth.lpfnMixAudioProc[1] = (Synth.wFormat & AUDIO_FORMAT_STEREO) ?
	    MixAudioData16SI : MixAudioData16MI;
    }
    else {
	Synth.lpfnMixAudioProc[0] = (Synth.wFormat & AUDIO_FORMAT_STEREO) ?
	    MixAudioData08S : MixAudioData08M;
	Synth.lpfnMixAudioProc[1] = (Synth.wFormat & AUDIO_FORMAT_STEREO) ?
	    MixAudioData16S : MixAudioData16M;
    }

    /* allocate volume (0-64) and filter (0-31) table */
    Synth.lpMemory = malloc(sizeof(LONG) * 65 * 256 +
			    sizeof(BYTE) * 32 * 256 + 1023);
    if (Synth.lpMemory != NULL) {
	lpVolumeTable = (LPLONG) (((DWORD) Synth.lpMemory + 1023) & ~1023);
	lpFilterTable = (LPBYTE) (lpVolumeTable + 65 * 256);
	ASetAudioMixerValue(AUDIO_MIXER_MASTER_VOLUME, 96);
	ASetAudioCallback(UpdateVoices);
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_NOMEMORY;
}

static UINT AIAPI CloseAudio(VOID)
{
    if (Synth.lpMemory != NULL)
	free(Synth.lpMemory);
    memset(&Synth, 0, sizeof(Synth));
    return AUDIO_ERROR_NONE;
}

static UINT AIAPI SetAudioMixerValue(UINT nChannel, UINT nMixerValue)
{
    LPBYTE lpFilter;
    LPLONG lpVolume;
    UINT nVolume, nSample;
    LONG dwAccum, dwDelta;

    if (Synth.lpMemory == NULL)
	return AUDIO_ERROR_NOTSUPPORTED;

    /* master volume must be less than 256 units */
    if (nChannel != AUDIO_MIXER_MASTER_VOLUME || nMixerValue > 256)
	return AUDIO_ERROR_INVALPARAM;

    /* half dynamic range for mono output */
    if (!(Synth.wFormat & AUDIO_FORMAT_STEREO))
	nMixerValue >>= 1;

    /* build volume table (0-64) */
    lpVolume = lpVolumeTable;
    dwDelta = 0;
    for (nVolume = 0; nVolume <= 64; nVolume++, dwDelta += nMixerValue) {
	dwAccum = 0;
	for (nSample = 0; nSample < 128; nSample++, dwAccum += dwDelta)
	    *lpVolume++ = dwAccum >> 4;
	dwAccum = -dwAccum;
	for (nSample = 0; nSample < 128; nSample++, dwAccum += dwDelta)
	    *lpVolume++ = dwAccum >> 4;
    }

#ifdef __FILTER__
    /* build lowpass filter table (0-31) */
    lpFilter = lpFilterTable;
    for (nVolume = 0; nVolume < 32; nVolume++) {
	dwAccum = 0;
	for (nSample = 0; nSample < 128; nSample++, dwAccum += nVolume)
	    *lpFilter++ = dwAccum >> 5;
	dwAccum = -dwAccum;
	for (nSample = 0; nSample < 128; nSample++, dwAccum += nVolume)
	    *lpFilter++ = dwAccum >> 5;
    }
#endif

    return AUDIO_ERROR_NONE;
}

static UINT AIAPI OpenVoices(UINT nVoices)
{
    UINT nVoice;

    /*
     * Initialize waveform synthesizer structure for playback
     */
    if (nVoices >= 1 && nVoices <= AUDIO_MAX_VOICES) {
	Synth.nVoices = nVoices;
	for (nVoice = 0; nVoice < Synth.nVoices; nVoice++)
	    Synth.aVoices[nVoice].bControl = VOICE_STOP;
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALPARAM;
}

static UINT AIAPI CloseVoices(VOID)
{
    UINT nVoice;

    memset(Synth.aVoices, 0, sizeof(Synth.aVoices));
    for (nVoice = 0; nVoice < AUDIO_MAX_VOICES; nVoice++)
	Synth.aVoices[nVoice].bControl = VOICE_STOP;
    return AUDIO_ERROR_NONE;
}

static UINT AIAPI UpdateAudio(VOID)
{
    return AUDIO_ERROR_NONE;
}

static LONG AIAPI GetAudioDataAvail(VOID)
{
    return 0;
}

static UINT AIAPI CreateAudioData(LPAUDIOWAVE lpWave)
{
    if (lpWave != NULL) {
	lpWave->dwHandle = (DWORD) lpWave->lpData;
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI DestroyAudioData(LPAUDIOWAVE lpWave)
{
    if (lpWave != NULL && lpWave->dwHandle != 0) {
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI WriteAudioData(LPAUDIOWAVE lpWave, DWORD dwOffset, UINT nCount)
{
    if (lpWave != NULL && lpWave->dwHandle != 0) {
	/* anticlick removal work around */
	if (lpWave->wFormat & AUDIO_FORMAT_LOOP) {
	    *(LPSTR)(lpWave->dwHandle + lpWave->dwLoopEnd) =
		*(LPSTR)(lpWave->dwHandle + lpWave->dwLoopStart);
	}
	else if (dwOffset + nCount >= lpWave->dwLength) {
	    *(LPDWORD) (lpWave->dwHandle + lpWave->dwLength) = 0;
	}
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI PrimeVoice(UINT nVoice, LPAUDIOWAVE lpWave)
{
    LPVOICE lpVoice;

    if (nVoice < Synth.nVoices && lpWave != NULL && lpWave->dwHandle != 0) {
	lpVoice = &Synth.aVoices[nVoice];
	lpVoice->lpData = (LPVOID) lpWave->dwHandle;
	lpVoice->bControl = VOICE_STOP;
	lpVoice->dwAccum = 0;
	if (lpWave->wFormat & (AUDIO_FORMAT_LOOP | AUDIO_FORMAT_BIDILOOP)) {
	    lpVoice->dwLoopStart = lpWave->dwLoopStart;
	    lpVoice->dwLoopEnd = lpWave->dwLoopEnd;
	    lpVoice->bControl |= VOICE_LOOP;
	    if (lpWave->wFormat & AUDIO_FORMAT_BIDILOOP)
		lpVoice->bControl |= VOICE_BIDILOOP;
	}
	else {
	    lpVoice->dwLoopStart = lpWave->dwLength;
	    lpVoice->dwLoopEnd = lpWave->dwLength;
	}
	if (lpWave->wFormat & AUDIO_FORMAT_16BITS) {
	    lpVoice->dwLoopStart >>= 1;
	    lpVoice->dwLoopEnd >>= 1;
	    lpVoice->bControl |= VOICE_16BITS;
	}
	lpVoice->dwAccum <<= ACCURACY;
	lpVoice->dwLoopStart <<= ACCURACY;
	lpVoice->dwLoopEnd <<= ACCURACY;
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI StartVoice(UINT nVoice)
{
    if (nVoice < Synth.nVoices) {
	Synth.aVoices[nVoice].bControl &= ~VOICE_STOP;
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI StopVoice(UINT nVoice)
{
    if (nVoice < Synth.nVoices) {
	Synth.aVoices[nVoice].bControl |= VOICE_STOP;
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALHANDLE;

}

static UINT AIAPI SetVoicePosition(UINT nVoice, LONG dwPosition)
{
    if (nVoice < Synth.nVoices) {
	dwPosition <<= ACCURACY;
	if (dwPosition >= 0 && dwPosition < Synth.aVoices[nVoice].dwLoopEnd) {
	    Synth.aVoices[nVoice].dwAccum = dwPosition;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI SetVoiceFrequency(UINT nVoice, LONG dwFrequency)
{
    if (nVoice < Synth.nVoices) {
	if (dwFrequency >= AUDIO_MIN_FREQUENCY &&
	    dwFrequency <= AUDIO_MAX_FREQUENCY) {
	    Synth.aVoices[nVoice].dwFrequency = ((dwFrequency << ACCURACY) +
						 (Synth.nSampleRate >> 1)) / Synth.nSampleRate;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI SetVoiceVolume(UINT nVoice, UINT nVolume)
{
    if (nVoice < Synth.nVoices) {
	if (nVolume <= AUDIO_MAX_VOLUME) {
	    Synth.aVoices[nVoice].nVolume = nVolume >> 1;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI SetVoicePanning(UINT nVoice, UINT nPanning)
{
    if (nVoice < Synth.nVoices) {
	if (nPanning <= AUDIO_MAX_PANNING) {
	    Synth.aVoices[nVoice].nPanning = nPanning;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI GetVoicePosition(UINT nVoice, LPLONG lpdwPosition)
{
    if (nVoice < Synth.nVoices) {
	if (lpdwPosition != NULL) {
	    *lpdwPosition = Synth.aVoices[nVoice].dwAccum >> ACCURACY;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI GetVoiceFrequency(UINT nVoice, LPLONG lpdwFrequency)
{
    if (nVoice < Synth.nVoices) {
	if (lpdwFrequency != NULL) {
	    *lpdwFrequency = (Synth.aVoices[nVoice].dwFrequency *
			      Synth.nSampleRate) >> ACCURACY;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI GetVoiceVolume(UINT nVoice, LPUINT lpnVolume)
{
    if (nVoice < Synth.nVoices) {
	if (lpnVolume != NULL) {
	    *lpnVolume = Synth.aVoices[nVoice].nVolume << 1;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI GetVoicePanning(UINT nVoice, LPUINT lpnPanning)
{
    if (nVoice < Synth.nVoices) {
	if (lpnPanning != NULL) {
	    *lpnPanning = Synth.aVoices[nVoice].nPanning;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI GetVoiceStatus(UINT nVoice, LPBOOL lpnStatus)
{
    if (nVoice < Synth.nVoices) {
	if (lpnStatus != NULL) {
	    *lpnStatus = (Synth.aVoices[nVoice].bControl & VOICE_STOP) != 0;
	    return AUDIO_ERROR_NONE;
	}
	return AUDIO_ERROR_INVALPARAM;
    }
    return AUDIO_ERROR_INVALHANDLE;
}

static UINT AIAPI SetAudioTimerProc(LPFNAUDIOTIMER lpfnAudioTimer)
{
    Synth.lpfnAudioTimer = lpfnAudioTimer;
    return AUDIO_ERROR_NONE;
}

static UINT AIAPI SetAudioTimerRate(UINT nBPM)
{
    if (nBPM >= 0x20 && nBPM <= 0xFF) {
	Synth.dwTimerRate = Synth.nSampleRate;
	if (Synth.wFormat & AUDIO_FORMAT_STEREO)
	    Synth.dwTimerRate <<= 1;
	Synth.dwTimerRate = (5 * Synth.dwTimerRate) / (2 * nBPM);
	return AUDIO_ERROR_NONE;
    }
    return AUDIO_ERROR_INVALPARAM;
}

static VOID AIAPI UpdateVoices(LPBYTE lpData, UINT nCount)
{
    static LONG aBuffer[BUFFERSIZE];
    UINT nSamples;

    if (Synth.wFormat & AUDIO_FORMAT_16BITS)
	nCount >>= 1;
    while (nCount > 0) {
	if ((nSamples = nCount) > BUFFERSIZE)
	    nSamples = BUFFERSIZE;
	memset(aBuffer, 0, nSamples << 2);
	MixAudioVoices(aBuffer, nSamples);
	QuantAudioData(lpData, aBuffer, nSamples);
	lpData += nSamples << ((Synth.wFormat & AUDIO_FORMAT_16BITS) != 0);
	nCount -= nSamples;
    }
}


/*
 * Waveform synthesizer public interface
 */
AUDIOSYNTHDRIVER EmuSynthDriver =
{
    GetAudioCaps, PingAudio, OpenAudio, CloseAudio,
    UpdateAudio, OpenVoices, CloseVoices,
    SetAudioTimerProc, SetAudioTimerRate, SetAudioMixerValue,
    GetAudioDataAvail, CreateAudioData, DestroyAudioData,
    WriteAudioData, PrimeVoice, StartVoice, StopVoice,
    SetVoicePosition, SetVoiceFrequency, SetVoiceVolume,
    SetVoicePanning, GetVoicePosition, GetVoiceFrequency,
    GetVoiceVolume, GetVoicePanning, GetVoiceStatus
};