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av_rescale with user specified rounding

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Originally committed as revision 3481 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2004-09-19 16:38:54 +00:00
parent aa25a462b6
commit 1f0182250a
2 changed files with 30 additions and 9 deletions
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15
libavcodec/avcodec.h
View File

@ -230,6 +230,14 @@ enum Motion_Est_ID {
ME_X1 ME_X1
}; };
enum AVRounding {
AV_ROUND_ZERO = 0, ///< round toward zero
AV_ROUND_INF = 1, ///< round away from zero
AV_ROUND_DOWN = 2, ///< round toward -infinity
AV_ROUND_UP = 3, ///< round toward +infinity
AV_ROUND_NEAR_INF = 5, ///< round to nearest and halfway cases away from zero
};
typedef struct RcOverride{ typedef struct RcOverride{
int start_frame; int start_frame;
int end_frame; int end_frame;
@ -2061,11 +2069,16 @@ char av_get_pict_type_char(int pict_type);
int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max); int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max);
/** /**
* rescale a 64bit integer. * rescale a 64bit integer with rounding to nearest.
* a simple a*b/c isnt possible as it can overflow * a simple a*b/c isnt possible as it can overflow
*/ */
int64_t av_rescale(int64_t a, int64_t b, int64_t c); int64_t av_rescale(int64_t a, int64_t b, int64_t c);
/**
* rescale a 64bit integer with specified rounding.
* a simple a*b/c isnt possible as it can overflow
*/
int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding);
/** /**
* Interface for 0.5.0 version * Interface for 0.5.0 version

24
libavcodec/utils.c
View File

@ -822,25 +822,33 @@ int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max)
return den==0; return den==0;
} }
int64_t av_rescale(int64_t a, int64_t b, int64_t c){ int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd){
AVInteger ai, ci; AVInteger ai;
int64_t r=0;
assert(c > 0); assert(c > 0);
assert(b >=0); assert(b >=0);
assert(rnd >=0 && rnd<=5 && rnd!=4);
if(a<0) return -av_rescale(-a, b, c); if(a<0) return -av_rescale_rnd(-a, b, c, rnd ^ ((rnd>>1)&1));
if(rnd==AV_ROUND_NEAR_INF) r= c/2;
else if(rnd&1) r= c-1;
if(b<=INT_MAX && c<=INT_MAX){ if(b<=INT_MAX && c<=INT_MAX){
if(a<=INT_MAX) if(a<=INT_MAX)
return (a * b + c/2)/c; return (a * b + r)/c;
else else
return a/c*b + (a%c*b + c/2)/c; return a/c*b + (a%c*b + r)/c;
} }
ai= av_mul_i(av_int2i(a), av_int2i(b)); ai= av_mul_i(av_int2i(a), av_int2i(b));
ci= av_int2i(c); ai= av_add_i(ai, av_int2i(r));
ai= av_add_i(ai, av_shr_i(ci,1));
return av_i2int(av_div_i(ai, ci)); return av_i2int(av_div_i(ai, av_int2i(c)));
}
int64_t av_rescale(int64_t a, int64_t b, int64_t c){
return av_rescale_rnd(a, b, c, AV_ROUND_NEAR_INF);
} }
/* av_log API */ /* av_log API */