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FFT Plugin: Revamp the main code to rid it of 64-bit math. Use 32-bit kiss_fft_scalar because 16-bit integers are generally a poor choice for computation on-target. Simplify display code to speed it up. Add logarithmic frequency display (need keymappings, guessed on some). On dual-core, perform FFT on COP. Add some support function to fixedpoint.c. ... and stuff.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26470 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2010-06-02 08:34:10 +00:00
parent bbe6c5a5e2
commit 30e2f42c82
6 changed files with 999 additions and 788 deletions
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67
apps/fixedpoint.c
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@ -171,6 +171,35 @@ long fp_sqrt(long x, unsigned int fracbits)
return b;
}
/* Accurate int sqrt with only elementary operations. (the above
* routine fails badly without enough iterations, more iterations
* than this requires -- [give that one a FIXME]).
* Snagged from:
* http://www.devmaster.net/articles/fixed-point-optimizations/ */
unsigned long isqrt(unsigned long x)
{
/* Adding CLZ could optimize this further */
unsigned long g = 0;
int bshift = 15;
unsigned long b = 1ul << bshift;
do
{
unsigned long temp = (g + g + b) << bshift;
if (x > temp)
{
g += b;
x -= temp;
}
b >>= 1;
}
while (bshift--);
return g;
}
#endif /* PLUGIN or CODEC */
@ -256,6 +285,44 @@ long fp16_log(int x) {
y-=x>>15;
return y;
}
/**
* Fixed-point exponential
* taken from http://www.quinapalus.com/efunc.html
* "The code assumes integers are at least 32 bits long. The (non-negative)
* argument and the result of the function are both expressed as fixed-point
* values with 16 fractional bits. Notice that after 11 steps of the
* algorithm the constants involved become such that the code is simply
* doing a multiplication: this is explained in the note below.
* The extension to negative arguments is left as an exercise."
*/
long fp16_exp(int x)
{
int t,y;
y=0x00010000;
t=x-0x58b91; if(t>=0) x=t,y<<=8;
t=x-0x2c5c8; if(t>=0) x=t,y<<=4;
t=x-0x162e4; if(t>=0) x=t,y<<=2;
t=x-0x0b172; if(t>=0) x=t,y<<=1;
t=x-0x067cd; if(t>=0) x=t,y+=y>>1;
t=x-0x03920; if(t>=0) x=t,y+=y>>2;
t=x-0x01e27; if(t>=0) x=t,y+=y>>3;
t=x-0x00f85; if(t>=0) x=t,y+=y>>4;
t=x-0x007e1; if(t>=0) x=t,y+=y>>5;
t=x-0x003f8; if(t>=0) x=t,y+=y>>6;
t=x-0x001fe; if(t>=0) x=t,y+=y>>7;
if(x&0x100) y+=y>>8;
if(x&0x080) y+=y>>9;
if(x&0x040) y+=y>>10;
if(x&0x020) y+=y>>11;
if(x&0x010) y+=y>>12;
if(x&0x008) y+=y>>13;
if(x&0x004) y+=y>>14;
if(x&0x002) y+=y>>15;
if(x&0x001) y+=y>>16;
return y;
}
#endif /* PLUGIN */