diff options
| author | Thom Johansen <thomj@rockbox.org> | 2006-01-29 17:52:13 +0000 |
|---|---|---|
| committer | Thom Johansen <thomj@rockbox.org> | 2006-01-29 17:52:13 +0000 |
| commit | 65721f0b3573460d306528ff34aa395c45e94ea3 (patch) | |
| tree | ce1476b13c66ba067d3944fabaac949aa78afb11 /apps/eq_cf.S | |
| parent | a371ec3e77f7fcc6d498c747ad46ede7900e0bde (diff) | |
Slight change of coef format. Removed erronous hard code of channel
number in EQ filtering routine and added some minor changes.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@8486 a1c6a512-1295-4272-9138-f99709370657
Diffstat (limited to 'apps/eq_cf.S')
| -rw-r--r-- | apps/eq_cf.S | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/apps/eq_cf.S b/apps/eq_cf.S index 3876ca72d6..0a34d7707e 100644 --- a/apps/eq_cf.S +++ b/apps/eq_cf.S @@ -26,21 +26,24 @@ eq_filter: movem.l (11*4+16, %sp), %d6-%d7 | load num. channels and shift count movem.l (%a5), %a0-%a4 | load coefs lea.l (5*4, %a5), %a5 | point to filter history - moveq.l #2, %d6 | number of channels (hardcode to stereo) .filterloop: move.l (11*4+4, %sp), %a6 | load input channel pointer + addq.l #4, (11*4+4, %sp) | point x to next channel move.l (%a6), %a6 move.l (11*4+12, %sp), %d5 | number of samples - addq.l #4, (11*4+4, %sp) | point x to next channel movem.l (%a5), %d0-%d3 | load filter history .loop: - move.l (%a6), %d4 - mac.l %a0, %d4, %acc0 | acc = b0*x[i] - mac.l %a1, %d0, %acc0 | acc += b1*x[i - 1] + /* Direct form 1 filtering code. We assume DSP has put EMAC in frac mode. + y[n] = b0*x[i] + b1*x[i - 1] + b2*x[i - 2] + a1*y[i - 1] + a2*y[i - 2], + where y[] is output and x[] is input. This is performed out of order + to do parallel load of input value. + */ + mac.l %a1, %d0, (%a6), %d4, %acc0 | acc = b1*x[i - 1], x[i] -> d4 mac.l %a2, %d1, %acc0 | acc += b2*x[i - 2] - msac.l %a3, %d2, %acc0 | acc -= a1*y[i - 1] - msac.l %a4, %d3, %acc0 | acc -= a2*y[i - 2] + mac.l %a0, %d4, %acc0 | acc += b0*x[i] + mac.l %a3, %d2, %acc0 | acc += a1*y[i - 1] + mac.l %a4, %d3, %acc0 | acc += a2*y[i - 2] move.l %d0, %d1 | fix history move.l %d4, %d0 move.l %d2, %d3 |