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Some entropy decoder tweaks. Also removed unnecessary 'tmp' variables.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19008 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jens Arnold 2008-11-04 23:46:04 +00:00
parent 1e8be6f6b0
commit 7a835ee0c6
2 changed files with 17 additions and 24 deletions
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13
apps/codecs/demac/libdemac/entropy.c
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@ -141,10 +141,13 @@ static inline void update_rice(struct rice_t* rice, int x)
if (rice->k == 0) { if (rice->k == 0) {
rice->k = 1; rice->k = 1;
} else if (rice->ksum < ((uint32_t)1 << (rice->k + 4))) { } else {
rice->k--; uint32_t lim = 1 << (rice->k + 4);
} else if (rice->ksum >= ((uint32_t)1 << (rice->k + 5))) { if (rice->ksum < lim) {
rice->k++; rice->k--;
} else if (rice->ksum >= 2 * lim) {
rice->k++;
}
} }
} }
@ -178,7 +181,7 @@ static inline int entropy_decode3980(struct rice_t* rice)
base_hi = range_decode_culfreq((pivot >> lo_bits) + 1); base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
range_decode_update(1, base_hi); range_decode_update(1, base_hi);
base_lo = range_decode_culfreq(1 << lo_bits); base_lo = range_decode_culshift(lo_bits);
range_decode_update(1, base_lo); range_decode_update(1, base_lo);
base = (base_hi << lo_bits) + base_lo; base = (base_hi << lo_bits) + base_lo;

28
apps/codecs/demac/libdemac/rangecoding.h
View file

@ -62,12 +62,9 @@ static int bytebufferoffset IBSS_ATTR;
static inline void skip_byte(void) static inline void skip_byte(void)
{ {
if (bytebufferoffset) { bytebufferoffset--;
bytebufferoffset--; bytebuffer += bytebufferoffset & 4;
} else { bytebufferoffset &= 3;
bytebufferoffset = 3;
bytebuffer += 4;
}
} }
static inline int read_byte(void) static inline int read_byte(void)
@ -122,23 +119,17 @@ static inline void range_dec_normalize(void)
/* or: totf is (code_value)1<<shift */ /* or: totf is (code_value)1<<shift */
/* returns the culmulative frequency */ /* returns the culmulative frequency */
static inline int range_decode_culfreq(int tot_f) static inline int range_decode_culfreq(int tot_f)
{ int tmp; {
range_dec_normalize(); range_dec_normalize();
rc.help = rc.range / tot_f; rc.help = rc.range / tot_f;
tmp = rc.low / rc.help; return rc.low / rc.help;
return tmp;
} }
static inline int range_decode_culshift(int shift) static inline int range_decode_culshift(int shift)
{ {
int tmp;
range_dec_normalize(); range_dec_normalize();
rc.help = rc.range>>shift; rc.help = rc.range >> shift;
tmp = rc.low/rc.help; return rc.low / rc.help;
return tmp;
} }
@ -146,9 +137,8 @@ static inline int range_decode_culshift(int shift)
/* sy_f is the interval length (frequency of the symbol) */ /* sy_f is the interval length (frequency of the symbol) */
/* lt_f is the lower end (frequency sum of < symbols) */ /* lt_f is the lower end (frequency sum of < symbols) */
static inline void range_decode_update(int sy_f, int lt_f) static inline void range_decode_update(int sy_f, int lt_f)
{ int tmp; {
tmp = rc.help * lt_f; rc.low -= rc.help * lt_f;
rc.low -= tmp;
rc.range = rc.help * sy_f; rc.range = rc.help * sy_f;
} }