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Change loop structure for sample synthesizing. Gives a nice speedup on both coldfire and arm targets.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@15036 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Nils Wallménius 2007-10-08 19:28:41 +00:00
parent d712e252fe
commit f619f81676
3 changed files with 64 additions and 76 deletions
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46
apps/plugins/midi/synth.c
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@ -255,8 +255,7 @@ inline void stopVoice(struct SynthObject * so)
so->decay = 0;
}
int synthVoice(struct SynthObject * so) ICODE_ATTR;
int synthVoice(struct SynthObject * so)
static inline int synthVoice(struct SynthObject * so)
{
struct GWaveform * wf;
register int s;
@ -404,3 +403,46 @@ int synthVoice(struct SynthObject * so)
return s*so->volscale>>14;
}
/* synth num_samples samples and write them to the */
/* buffer pointed to by buf_ptr */
void synthSamples(int32_t *buf_ptr, unsigned int num_samples) ICODE_ATTR;
void synthSamples(int32_t *buf_ptr, unsigned int num_samples)
{
int i;
register int dL;
register int dR;
register int sample;
register struct SynthObject *voicept;
while(num_samples>0)
{
dL=0;
dR=0;
voicept=&voices[0];
for(i=MAX_VOICES; i > 0; i--)
{
if(voicept->isUsed==1)
{
sample = synthVoice(voicept);
dL += sample;
sample *= chPan[voicept->ch];
dR += sample;
}
voicept++;
}
dL = (dL << 7) - dR;
/* combine the left and right 16 bit samples into 32 bits and write */
/* to the buffer, left sample in the high word and right in the low word */
*buf_ptr=(((dL&0x7FFF80) << 9) | ((dR&0x7FFF80) >> 7));
buf_ptr++;
num_samples--;
}
/* TODO: Automatic Gain Control, anyone? */
/* Or, should this be implemented on the DSP's output volume instead? */
return; /* No more ghetto lowpass filter. Linear interpolation works well. */
}