1 files changed, 25 insertions, 7 deletions

diff --git a/libavutil/tests/lfg.c b/libavutil/tests/lfg.c
index 9a0c47c4de..1425e026b4 100644
--- a/libavutil/tests/lfg.c
+++ b/libavutil/tests/lfg.c
@@ -1,18 +1,18 @@
 /*
- * This file is part of Libav.
+ * This file is part of FFmpeg.
  *
- * Libav is free software; you can redistribute it and/or
+ * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
- * Libav is distributed in the hope that it will be useful,
+ * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
- * License along with Libav; if not, write to the Free Software
+ * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
@@ -29,8 +29,10 @@ int main(void)
     av_lfg_init(&state, 0xdeadbeef);
     for (j = 0; j < 10000; j++) {
         START_TIMER
-        for (i = 0; i < 624; i++)
+        for (i = 0; i < 624; i++) {
+            //av_log(NULL, AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
             x += av_lfg_get(&state);
+        }
         STOP_TIMER("624 calls of av_lfg_get");
     }
     av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
@@ -39,17 +41,33 @@ int main(void)
     {
         double mean   = 1000;
         double stddev = 53;
+        double samp_mean = 0.0, samp_stddev = 0.0;
+        double samp0, samp1;
 
         av_lfg_init(&state, 42);
 
         for (i = 0; i < 1000; i += 2) {
             double bmg_out[2];
             av_bmg_get(&state, bmg_out);
+            samp0 = bmg_out[0] * stddev + mean;
+            samp1 = bmg_out[1] * stddev + mean;
+            samp_mean += samp0 + samp1;
+            samp_stddev += samp0 * samp0 + samp1 * samp1;
             av_log(NULL, AV_LOG_INFO,
                    "%f\n%f\n",
-                   bmg_out[0] * stddev + mean,
-                   bmg_out[1] * stddev + mean);
+                   samp0,
+                   samp1);
         }
+        /* TODO: add proper normality test */
+        samp_mean /= 1000;
+        samp_stddev /= 999;
+        samp_stddev -= (1000.0/999.0)*samp_mean*samp_mean;
+        samp_stddev = sqrt(samp_stddev);
+        av_log(NULL, AV_LOG_INFO, "sample mean  : %f\n"
+                                  "true mean    : %f\n"
+                                  "sample stddev: %f\n"
+                                  "true stddev  : %f\n",
+                                   samp_mean, mean, samp_stddev, stddev);
     }
 
     return 0;