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Small correction to avoid overflow within calculate_V()-function. Re-enable full precision for ARM as speed-optimized version is not that much faster anymore.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17750 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Andree Buschmann 2008-06-22 09:11:06 +00:00
parent 5acfae2a3c
commit f0087f06aa
2 changed files with 5 additions and 3 deletions
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2
apps/codecs/libmusepack/mpc_config.h
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@ -37,7 +37,7 @@
#if defined(CPU_COLDFIRE)
// do nothing
#elif defined(CPU_ARM)
#define OPTIMIZE_FOR_SPEED
//#define OPTIMIZE_FOR_SPEED
#else
#define OPTIMIZE_FOR_SPEED
#endif

6
apps/codecs/libmusepack/synth_filter.c
View file

@ -115,8 +115,8 @@ static const MPC_SAMPLE_FORMAT Di_opt [512] ICONST_ATTR = {
#undef D
// needed to prevent from internal overflow in calculate_V
#define OVERFLOW_FIX 1
// needed to prevent from internal overflow in calculate_V (see below)
#define OVERFLOW_FIX 2
// V-coefficients were expanded (<<) by V_COEFFICIENT_EXPAND
#define V_COEFFICIENT_EXPAND 27
@ -128,6 +128,7 @@ static const MPC_SAMPLE_FORMAT Di_opt [512] ICONST_ATTR = {
#define MPC_MULTIPLY_V(sample, vcoef) ( MPC_SHR_RND(sample, 12) * vcoef )
// pre- and postscale are used to avoid internal overflow in synthesis calculation
// samples are s15.0, v-coefs are 4.12 -> internal format is s19.12
#define MPC_MULTIPLY_V_PRESCALE(sample, vcoef) ( MPC_SHR_RND(sample, (12+OVERFLOW_FIX)) * vcoef )
#define MPC_MULTIPLY_V_POSTSCALE(sample, vcoef) ( MPC_SHR_RND(sample, (12-OVERFLOW_FIX)) * vcoef )
#define MPC_V_POSTSCALE(sample) (sample<<OVERFLOW_FIX)
@ -141,6 +142,7 @@ static const MPC_SAMPLE_FORMAT Di_opt [512] ICONST_ATTR = {
#define MPC_MULTIPLY_V(sample, vcoef) ( (MPC_MULTIPLY_FRACT(sample, vcoef)) << (32-V_COEFFICIENT_EXPAND) )
// pre- and postscale are used to avoid internal overflow in synthesis calculation
// samples are s15.14, v-coefs are 4.27 -> internal format is s19.12
#define MPC_MULTIPLY_V_PRESCALE(sample, vcoef) ( (MPC_MULTIPLY_FRACT(sample, vcoef)) << (32-V_COEFFICIENT_EXPAND-OVERFLOW_FIX) )
#define MPC_MULTIPLY_V_POSTSCALE(sample, vcoef) ( (MPC_MULTIPLY_FRACT(sample, vcoef)) << (32-V_COEFFICIENT_EXPAND+OVERFLOW_FIX) )
#define MPC_V_POSTSCALE(sample) (sample<<OVERFLOW_FIX)