Add additional encoding options, based on upstream PR streamio#197

Author: jribar

lib/ffmpeg/encoding_options.rb

@@ -181,6 +181,22 @@ def convert_watermark(value)
       ['-i', value]
     end
 
+    def convert_x264_vprofile_level(value)
+      ['-level', value]
+    end
+
+    def convert_constant_rate_factor(value)
+      ['-crf', value]
+    end
+
+    def convert_reference_frames(value)
+      ['-refs', value]
+    end
+
+    def convert_strict(value)
+      value ? %w[-strict -2] : []
+    end
+
     def convert_watermark_filter(value)
       position = value[:position]
       padding_x = value[:padding_x] || 10