Use M_PI from libavutil/mathematics.h instead of defining PI ourselves

in libavcodec/apiexample.c.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@15520 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/apiexample.c

@@ -30,15 +30,13 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
-#include <math.h>
-
-#define PI 3.14159265358979323846
 
 #ifdef HAVE_AV_CONFIG_H
 #undef HAVE_AV_CONFIG_H
 #endif
 
 #include "avcodec.h"
+#include "libavutil/mathematics.h"
 
 #define INBUF_SIZE 4096
 
@@ -91,7 +89,7 @@ void audio_encode_example(const char *filename)
 
     /* encode a single tone sound */
     t = 0;
-    tincr = 2 * PI * 440.0 / c->sample_rate;
+    tincr = 2 * M_PI * 440.0 / c->sample_rate;
     for(i=0;i<200;i++) {
         for(j=0;j<frame_size;j++) {
             samples[2*j] = (int)(sin(t) * 10000);