V2.0.4 centos version

+#帧率
+ fps = 20 
+#关键帧间隔，默认与fps一致，即每秒一个关键帧
+ gop_size = 20
+
+#视频码率
+ bit_rate = 256000
+ 
+#视频预设值编码参数: ultrafast、superfast、veryfast、faster、fast、medium、slow、slower、veryslow、placebo
+ preset = ultrafast 
+
+#音频采样率
+ a_sample_rate = 48000
+
+ #音频码率
+ a_bit_rate = 64000