soundux.cpp

著名SFC模拟器Snes9x的源代码。

    signed char *compressed = (signed char *) &IAPU.RAM [ch->block_pointer];

    unsigned char filter = *compressed;
    if ((ch->last_block = filter & 1))
	ch->loop = (filter & 2) != 0;

#if (defined (__linux__) && (defined (__i386__) || defined (__i486__) ||\
     defined (__i586__))) || defined (__WIN32__)
    int16 *raw = ch->block = ch->decoded;

    DecodeBlockAsm (compressed, raw, &ch->previous [0], &ch->previous [1]);
#else
    int32 out;
    unsigned char shift;
    signed char sample1, sample2;
    unsigned int i;

    // If enabled, results in 'tick' sound on some samples that repeat by
    // re-using part of the original sample but generate a slightly different
    // waveform.
    if (!Settings.DisableSampleCaching &&
	memcmp ((uint8 *) compressed, &IAPU.ShadowRAM [ch->block_pointer], 9) == 0)
    {
	ch->block = (signed short *) (IAPU.CachedSamples + (ch->block_pointer << 2));
	ch->previous [0] = ch->block [15];
	ch->previous [1] = ch->block [14];
    }
    else
    {
	if (!Settings.DisableSampleCaching)
	    memcpy (&IAPU.ShadowRAM [ch->block_pointer], (uint8 *) compressed, 9);
	compressed++;
	signed short *raw = ch->block = ch->decoded;
	
	int32 prev0 = ch->previous [0];
	int32 prev1 = ch->previous [1];
	shift = filter >> 4;

	switch ((filter >> 2) & 3)
	{
        case 0:
	    for (i = 8; i != 0; i--)
	    {
		sample1 = *compressed++;
		sample2 = sample1 << 4;
		sample2 >>= 4;
		sample1 >>= 4;
		*raw++ = ((int32) sample1 << shift);
		*raw++ = ((int32) sample2 << shift);
	    }
	    prev1 = *(raw - 2);
	    prev0 = *(raw - 1);
	    break;
	case 1:
	    for (i = 8; i != 0; i--)
	    {
		sample1 = *compressed++;
		sample2 = sample1 << 4;
		sample2 >>= 4;
		sample1 >>= 4;
		prev0 = (int16) prev0;
		*raw++ = prev1 = ((int32) sample1 << shift) + prev0 - (prev0 >> 4);
		prev1 = (int16) prev1;
		*raw++ = prev0 = ((int32) sample2 << shift) + prev1 - (prev1 >> 4);
	    }
	    break;
        case 2:
	    for (i = 8; i != 0; i--)
	    {
		sample1 = *compressed++;
		sample2 = sample1 << 4;
		sample2 >>= 4;
		sample1 >>= 4;
		
		out = (sample1 << shift) - prev1 + (prev1 >> 4);
		prev1 = (int16) prev0;
		*raw++ = prev0 = out + (prev0 << 1) - (prev0 >> 5) - 
				 (prev0 >> 4);

		out = (sample2 << shift) - prev1 + (prev1 >> 4);
		prev1 = (int16) prev0;
		*raw++ = prev0 = out + (prev0 << 1) - (prev0 >> 5) -
			         (prev0 >> 4);
	    }
	    break;
	case 3:
	    for (i = 8; i != 0; i--)
	    {
		sample1 = *compressed++;
		sample2 = sample1 << 4;
		sample2 >>= 4;
		sample1 >>= 4;
		out = (sample1 << shift);

		out = out - prev1 + (prev1 >> 3) + (prev1 >> 4);
		prev1 = (int16) prev0;
		*raw++ = prev0 = out + (prev0 << 1) - (prev0 >> 3) - 
			         (prev0 >> 4) - (prev1 >> 6);

		out = (sample2 << shift);
		out = out - prev1 + (prev1 >> 3) + (prev1 >> 4);
		prev1 = (int16) prev0;
		*raw++ = prev0 = out + (prev0 << 1) - (prev0 >> 3) - 
			         (prev0 >> 4) - (prev1 >> 6);
	    }
	    break;
	}
	ch->previous [0] = prev0;
	ch->previous [1] = prev1;

	if (!Settings.DisableSampleCaching)
	{
	    memcpy (IAPU.CachedSamples + (ch->block_pointer << 2),
		    (uint8 *) ch->decoded, 32);
	}
    }
#endif

    ch->block_pointer += 9;
}

void DecodeBlock (Channel *ch)
{
    int32 out;
    unsigned char filter;
    unsigned char shift;
    signed char sample1, sample2;
    unsigned char i;

    if (Settings.AltSampleDecode)
    {
        AltDecodeBlock (ch);
        return;
    }
    if (ch->block_pointer > 0x10000 - 9)
    {
	ch->last_block = TRUE;
	ch->loop = FALSE;
	ch->block = ch->decoded;
	return;
    }
    signed char *compressed = (signed char *) &IAPU.RAM [ch->block_pointer];

    filter = *compressed;
    if ((ch->last_block = filter & 1))
	ch->loop = (filter & 2) != 0;

    // If enabled, results in 'tick' sound on some samples that repeat by
    // re-using part of the original sample but generate a slightly different
    // waveform.
    if (!Settings.DisableSampleCaching &&
	memcmp ((uint8 *) compressed, &IAPU.ShadowRAM [ch->block_pointer], 9) == 0)
    {
	ch->block = (signed short *) (IAPU.CachedSamples + (ch->block_pointer << 2));
	ch->previous [0] = ch->block [15];
	ch->previous [1] = ch->block [14];
    }
    else
    {
	if (!Settings.DisableSampleCaching)
	    memcpy (&IAPU.ShadowRAM [ch->block_pointer], (uint8 *) compressed, 9);
	compressed++;
	signed short *raw = ch->block = ch->decoded;

	shift = filter >> 4;
	filter = ((filter >> 2) & 3);
	int32 prev0 = ch->previous [0];
	int32 prev1 = ch->previous [1];
	int32 f0 = FilterValues[filter][0];
	int32 f1 = FilterValues[filter][1];

	for (i = 8; i != 0; i--)
	{
	    sample1 = *compressed++;
	    sample2 = sample1 << 4;
	    //Sample 2 = Bottom Nibble, Sign Extended.
	    sample2 >>= 4;
	    //Sample 1 = Top Nibble, shifted down and Sign Extended.
	    sample1 >>= 4;
	    out = (sample1 << shift);
	    out += (prev0 * f0 + prev1 * f1) / 256;

	    CLIP16 (out);
	    prev1 = prev0;
	    prev0 = out;
	    *raw++ = (signed short) out;

	    out = (sample2 << shift);
	    out += (prev0 * f0 + prev1 * f1) / 256;

	    CLIP16 (out);
	    prev1 = prev0;
	    prev0 = out;
	    *raw++ = (signed short) out;
	}
	ch->previous [0] = prev0;
	ch->previous [1] = prev1;

	if (!Settings.DisableSampleCaching)
	{
	    memcpy (IAPU.CachedSamples + (ch->block_pointer << 2),
		    (uint8 *) ch->decoded, 32);
	}
    }
    ch->block_pointer += 9;
}

void MixStereo (int sample_count)
{
#if defined(TARGET_OS_MAC) && TARGET_OS_MAC
    static int wave[SOUND_BUFFER_SIZE];
#else
    int wave[SOUND_BUFFER_SIZE];
#endif
    int pitch_mod = SoundData.pitch_mod & ~APU.DSP[APU_NON];

    for (uint32 J = 0; J < NUM_CHANNELS; J++) 
    {
	int32 VL, VR;
	Channel *ch = &SoundData.channels[J];
	unsigned long freq0 = ch->frequency;

	if (ch->state == SOUND_SILENT || !(so.sound_switch & (1 << J)))
	    continue;

//	freq0 = (unsigned long) ((double) freq0 * 0.985);

	bool8 mod = pitch_mod & (1 << J);

	if (ch->needs_decode) 
	{
	    DecodeBlock(ch);
	    ch->needs_decode = FALSE;
	    ch->sample = ch->block[0];
	    ch->sample_pointer = freq0 >> FIXED_POINT_SHIFT;
	    if (ch->sample_pointer == 0)
		ch->sample_pointer = 1;
	    if (ch->sample_pointer > SOUND_DECODE_LENGTH)
		ch->sample_pointer = SOUND_DECODE_LENGTH - 1;

	    ch->next_sample = ch->block[ch->sample_pointer];
	    ch->interpolate = 0;

	    if (Settings.InterpolatedSound && freq0 < FIXED_POINT && !mod)
		ch->interpolate = ((ch->next_sample - ch->sample) * 
				   (long) freq0) / (long) FIXED_POINT;
	}
	VL = (ch->sample * ch-> left_vol_level) / 128;
	VR = (ch->sample * ch->right_vol_level) / 128;

	for (uint32 I = 0; I < (uint32) sample_count; I += 2)
	{
	    unsigned long freq = freq0;

	    if (mod)
		freq = PITCH_MOD(freq, wave [I / 2]);

	    ch->env_error += ch->erate;
	    if (ch->env_error >= FIXED_POINT) 
	    {
		uint32 step = ch->env_error >> FIXED_POINT_SHIFT;

		switch (ch->state)
		{
		case SOUND_ATTACK:
		    ch->env_error &= FIXED_POINT_REMAINDER;
		    ch->envx += step << 1;
		    ch->envxx = ch->envx << ENVX_SHIFT;

		    if (ch->envx >= 126)
		    {
			ch->envx = 127;
			ch->envxx = 127 << ENVX_SHIFT;
			ch->state = SOUND_DECAY;
			if (ch->sustain_level != 8) 
			{
			    S9xSetEnvRate (ch, ch->decay_rate, -1,
						(MAX_ENVELOPE_HEIGHT * ch->sustain_level)
						>> 3);
			    break;
			}
			ch->state = SOUND_SUSTAIN;
			S9xSetEnvRate (ch, ch->sustain_rate, -1, 0);
		    }
		    break;
		
		case SOUND_DECAY:
		    while (ch->env_error >= FIXED_POINT)
		    {
			ch->envxx = (ch->envxx >> 8) * 255;
			ch->env_error -= FIXED_POINT;
		    }
		    ch->envx = ch->envxx >> ENVX_SHIFT;
		    if (ch->envx <= ch->envx_target)
		    {
			if (ch->envx <= 0)
			{
			    S9xAPUSetEndOfSample (J, ch);
			    goto stereo_exit;
			}
			ch->state = SOUND_SUSTAIN;
			S9xSetEnvRate (ch, ch->sustain_rate, -1, 0);
		    }
		    break;

		case SOUND_SUSTAIN:
		    while (ch->env_error >= FIXED_POINT)
		    {
			ch->envxx = (ch->envxx >> 8) * 255;
			ch->env_error -= FIXED_POINT;
		    }
		    ch->envx = ch->envxx >> ENVX_SHIFT;
		    if (ch->envx <= 0)
		    {
			S9xAPUSetEndOfSample (J, ch);
			goto stereo_exit;
		    }
		    break;
		    
		case SOUND_RELEASE:
		    while (ch->env_error >= FIXED_POINT)
		    {
			ch->envxx -= (MAX_ENVELOPE_HEIGHT << ENVX_SHIFT) / 256;
			ch->env_error -= FIXED_POINT;
		    }
		    ch->envx = ch->envxx >> ENVX_SHIFT;
		    if (ch->envx <= 0)
		    {
			S9xAPUSetEndOfSample (J, ch);
			goto stereo_exit;
		    }
		    break;
		
		case SOUND_INCREASE_LINEAR:
		    ch->env_error &= FIXED_POINT_REMAINDER;
		    ch->envx += step << 1;
		    ch->envxx = ch->envx << ENVX_SHIFT;

		    if (ch->envx >= 126)
		    {
			ch->envx = 127;
			ch->envxx = 127 << ENVX_SHIFT;
			ch->state = SOUND_GAIN;
			ch->mode = MODE_GAIN;
			S9xSetEnvRate (ch, 0, -1, 0);
		    }
		    break;

		case SOUND_INCREASE_BENT_LINE:
		    if (ch->envx >= (MAX_ENVELOPE_HEIGHT * 3) / 4)
		    {
			while (ch->env_error >= FIXED_POINT)
			{
			    ch->envxx += (MAX_ENVELOPE_HEIGHT << ENVX_SHIFT) / 256;
			    ch->env_error -= FIXED_POINT;
			}
			ch->envx = ch->envxx >> ENVX_SHIFT;
		    }
		    else
		    {
			ch->env_error &= FIXED_POINT_REMAINDER;
			ch->envx += step << 1;
			ch->envxx = ch->envx << ENVX_SHIFT;
		    }

		    if (ch->envx >= 126)
		    {
			ch->envx = 127;
			ch->envxx = 127 << ENVX_SHIFT;
			ch->state = SOUND_GAIN;
			ch->mode = MODE_GAIN;
			S9xSetEnvRate (ch, 0, -1, 0);
		    }
		    break;

		case SOUND_DECREASE_LINEAR:
		    ch->env_error &= FIXED_POINT_REMAINDER;
		    ch->envx -= step << 1;
		    ch->envxx = ch->envx << ENVX_SHIFT;
		    if (ch->envx <= 0)
		    {
			S9xAPUSetEndOfSample (J, ch);
			goto stereo_exit;
		    }
		    break;

		case SOUND_DECREASE_EXPONENTIAL:
		    while (ch->env_error >= FIXED_POINT)
		    {
			ch->envxx = (ch->envxx >> 8) * 255;
			ch->env_error -= FIXED_POINT;
		    }
		    ch->envx = ch->envxx >> ENVX_SHIFT;
		    if (ch->envx <= 0)
		    {
			S9xAPUSetEndOfSample (J, ch);
			goto stereo_exit;
		    }
		    break;
		
		case SOUND_GAIN:
		    S9xSetEnvRate (ch, 0, -1, 0);
		    break;
		}
		ch-> left_vol_level = (ch->envx * ch->volume_left) / 128;
		ch->right_vol_level = (ch->envx * ch->volume_right) / 128;
		VL = (ch->sample * ch-> left_vol_level) / 128;
		VR = (ch->sample * ch->right_vol_level) / 128;
	    }

	    ch->count += freq;
	    if (ch->count >= FIXED_POINT)
	    {
		VL = ch->count >> FIXED_POINT_SHIFT;
		ch->sample_pointer += VL;
		ch->count &= FIXED_POINT_REMAINDER;

		ch->sample = ch->next_sample;
		if (ch->sample_pointer >= SOUND_DECODE_LENGTH)
		{
		    if (JUST_PLAYED_LAST_SAMPLE(ch))
		    {
			S9xAPUSetEndOfSample (J, ch);
			goto stereo_exit;
		    }
		    do
		    {
			ch->sample_pointer -= SOUND_DECODE_LENGTH;
			if (ch->last_block)
			{
			    if (!ch->loop)
			    {
				ch->sample_pointer = LAST_SAMPLE;
				ch->next_sample = ch->sample;
				break;
			    }
			    else
			    {
				S9xAPUSetEndX (J);
				ch->last_block = FALSE;
				uint8 *dir = S9xGetSampleAddress (ch->sample_number);
				ch->block_pointer = READ_WORD(dir + 2);
			    }
			}
			DecodeBlock (ch);
		    } while (ch->sample_pointer >= SOUND_DECODE_LENGTH);
		    if (!JUST_PLAYED_LAST_SAMPLE (ch))
			ch->next_sample = ch->block [ch->sample_pointer];
		}
		else
		    ch->next_sample = ch->block [ch->sample_pointer];

		if (ch->type == SOUND_SAMPLE)