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Add a more correct absolute difference function to dsp-util.

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Differences between signed samples cover the entire unsigned 32-bit
range. "abs" will think any difference exceeding INT32_MAX is negative
which is not corrent. Test which argument is greater and subtract the
lesser from it, outputting unsigned difference.

Change-Id: I73a8e5e418d49ff73d1a7c98eeb4731946dcfe84
This commit is contained in:
Michael Sevakis 2012-04-26 15:21:43 -04:00
parent 2866063c3c
commit e5c3327cef
2 changed files with 13 additions and 7 deletions
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13
firmware/export/dsp-util.h
View file

@ -18,8 +18,8 @@
* KIND, either express or implied. * KIND, either express or implied.
* *
****************************************************************************/ ****************************************************************************/
#ifndef DSP_HELPER_H #ifndef DSP_UTIL_H
#define DSP_HELPER_H #define DSP_UTIL_H
/** Clip sample to signed 16 bit range **/ /** Clip sample to signed 16 bit range **/
@ -48,4 +48,11 @@ static FORCE_INLINE int32_t clip_sample_16(int32_t sample)
#undef CLIP_SAMPLE_16_DEFINED #undef CLIP_SAMPLE_16_DEFINED
#endif /* DSP_HELPER_H */ /* Absolute difference of signed 32-bit numbers which must be dealt with
* in the unsigned 32-bit range */
static FORCE_INLINE uint32_t ad_s32(int32_t a, int32_t b)
{
return (a >= b) ? (a - b) : (b - a);
}
#endif /* DSP_UTIL_H */

7
lib/rbcodec/dsp/tdspeed.c
View file

@ -29,6 +29,7 @@
#include "system.h" #include "system.h"
#include "tdspeed.h" #include "tdspeed.h"
#include "settings.h" #include "settings.h"
#include "dsp-util.h"
#define assert(cond) #define assert(cond)
@ -308,8 +309,7 @@ static int tdspeed_apply(int32_t *buf_out[2], int32_t *buf_in[2],
for (int j = 0; j < st->dst_step; j += INC2, curr += INC2, prev += INC2) for (int j = 0; j < st->dst_step; j += INC2, curr += INC2, prev += INC2)
{ {
int32_t diff = *curr - *prev; delta += ad_s32(*curr, *prev);
delta += abs(diff);
if (delta >= min_delta) if (delta >= min_delta)
goto skip; goto skip;
@ -322,8 +322,7 @@ static int tdspeed_apply(int32_t *buf_out[2], int32_t *buf_in[2],
for (int j = 0; j < st->dst_step; j += INC2, curr += INC2, prev += INC2) for (int j = 0; j < st->dst_step; j += INC2, curr += INC2, prev += INC2)
{ {
int32_t diff = *curr - *prev; delta += ad_s32(*curr, *prev);
delta += abs(diff);
if (delta >= min_delta) if (delta >= min_delta)
goto skip; goto skip;