[FFmpeg-devel] [PATCH] all: use predefined mathematics macros

[Michael Niedermayer]

On Tue, Nov 10, 2015 at 10:35:23PM -0500, Ganesh Ajjanagadde wrote:
> This uses M_SQRT2, M_PI, and M_E instead of the actual literals.
> Benefits include:
> 1. Reduced scope for copy/paste errors and improved readability.
> 2. Consistency across the codebase.
> 3. Actually fixes an incorrect sqrt(2) in avcodec/ppc.
> 4. Greater precision in avcodec/ac3.
> 
> Patch tested with FATE on x86, ppc untested.
> 
> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
> ---
>  libavcodec/ac3.h                   |  2 +-
>  libavcodec/cos_tablegen.c          |  4 +++-
>  libavcodec/mpegaudioenc_template.c |  4 ++--
>  libavcodec/mpegaudiotab.h          |  2 --
>  libavcodec/mpegvideo.c             |  4 ++--
>  libavcodec/ppc/fdctdsp.c           | 21 ++++++++++-----------
>  libavcodec/ratecontrol.c           |  4 ----
>  libavcodec/simple_idct.c           |  4 ++--
>  libavfilter/af_dynaudnorm.c        |  4 +---
>  9 files changed, 21 insertions(+), 28 deletions(-)
> 
[...]

> diff --git a/libavcodec/mpegaudioenc_template.c b/libavcodec/mpegaudioenc_template.c
> index ce93cc7..b91d0a8 100644
> --- a/libavcodec/mpegaudioenc_template.c
> +++ b/libavcodec/mpegaudioenc_template.c
> @@ -244,11 +244,11 @@ static void idct32(int *out, int *tab)
>      do {
>          int x1, x2, x3, x4;
>  
> -        x3 = MUL(t[16], FIX(SQRT2*0.5));
> +        x3 = MUL(t[16], FIX(M_SQRT2*0.5));
>          x4 = t[0] - x3;
>          x3 = t[0] + x3;
>  
> -        x2 = MUL(-(t[24] + t[8]), FIX(SQRT2*0.5));
> +        x2 = MUL(-(t[24] + t[8]), FIX(M_SQRT2*0.5));
>          x1 = MUL((t[8] - x2), xp[0]);
>          x2 = MUL((t[8] + x2), xp[1]);

ok if the FIX() values stay the same


>  
> diff --git a/libavcodec/mpegaudiotab.h b/libavcodec/mpegaudiotab.h
> index 42d42d8..bb2e5de 100644
> --- a/libavcodec/mpegaudiotab.h
> +++ b/libavcodec/mpegaudiotab.h
> @@ -33,8 +33,6 @@
>  #include <stdint.h>
>  #include "mpegaudio.h"
>  
> -#define SQRT2 1.41421356237309514547
> -
>  static const int costab32[30] = {
>      FIX(0.54119610014619701222),
>      FIX(1.3065629648763763537),

ok if all use of the macro are removed


> diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
> index 96634ec..69e0595 100644
> --- a/libavcodec/mpegvideo.c
> +++ b/libavcodec/mpegvideo.c
> @@ -1870,8 +1870,8 @@ void ff_print_debug_info2(AVCodecContext *avctx, AVFrame *pict, uint8_t *mbskip_
>                      uint64_t u,v;
>                      int y;
>  #define COLOR(theta, r) \
> -    u = (int)(128 + r * cos(theta * 3.141592 / 180)); \
> -    v = (int)(128 + r * sin(theta * 3.141592 / 180));
> +    u = (int)(128 + r * cos(theta * M_PI / 180)); \
> +    v = (int)(128 + r * sin(theta * M_PI / 180));
>  
>  
>                      u = v = 128;

ok


[...]
> diff --git a/libavcodec/ratecontrol.c b/libavcodec/ratecontrol.c
> index 308e34e..e96550c 100644
> --- a/libavcodec/ratecontrol.c
> +++ b/libavcodec/ratecontrol.c
> @@ -35,10 +35,6 @@
>  #include "mpegvideo.h"
>  #include "libavutil/eval.h"
>  
> -#ifndef M_E
> -#define M_E 2.718281828
> -#endif
> -
>  static int init_pass2(MpegEncContext *s);
>  static double get_qscale(MpegEncContext *s, RateControlEntry *rce,
>                           double rate_factor, int frame_num);

ok


> diff --git a/libavcodec/simple_idct.c b/libavcodec/simple_idct.c
> index 4d6d20d..0711e16 100644
> --- a/libavcodec/simple_idct.c
> +++ b/libavcodec/simple_idct.c
> @@ -132,7 +132,7 @@ void ff_simple_idct248_put(uint8_t *dest, int line_size, int16_t *block)
>  #undef C1
>  #undef C2
>  #define CN_SHIFT 12
> -#define C_FIX(x) ((int)((x) * 1.414213562 * (1 << CN_SHIFT) + 0.5))
> +#define C_FIX(x) ((int)((x) * M_SQRT2 * (1 << CN_SHIFT) + 0.5))
>  #define C1 C_FIX(0.6532814824)
>  #define C2 C_FIX(0.2705980501)
>  #define C3 C_FIX(0.5)
> @@ -159,7 +159,7 @@ static inline void idct4col_add(uint8_t *dest, int line_size, const int16_t *col
>  }
>  
>  #define RN_SHIFT 15
> -#define R_FIX(x) ((int)((x) * 1.414213562 * (1 << RN_SHIFT) + 0.5))
> +#define R_FIX(x) ((int)((x) * M_SQRT2 * (1 << RN_SHIFT) + 0.5))
>  #define R1 R_FIX(0.6532814824)
>  #define R2 R_FIX(0.2705980501)
>  #define R3 R_FIX(0.5)

this is ok if all calculated integer values stay the same

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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