Add control for video subsampling

Add '-s' to assign jpeg subsampling.
  0: 444, 1: 420

Using 420 will make video lack of detail compared to 444, but cut
amount of video data by half. This could be useful for some cases.

Change-Id: I48836a7117f7e3b9986e3f5c6a92974c9268525e
Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
diff --git a/ikvm_args.hpp b/ikvm_args.hpp
index fbe19ad..bfd5507 100644
--- a/ikvm_args.hpp
+++ b/ikvm_args.hpp
@@ -72,6 +72,16 @@
     }
 
     /*
+     * @brief Get the video subsampling
+     *
+     * @return Value of the video subsampling
+     */
+    inline int getSubsampling() const
+    {
+        return subsampling;
+    }
+
+    /*
      * @brief Get the path to the USB keyboard device
      *
      * @return Reference to the string storing the path to the keyboard device
@@ -120,6 +130,8 @@
      *        stream
      */
     int frameRate;
+    /* @brief Desired subsampling (0: 444, 1: 420) */
+    int subsampling;
     /* @brief Path to the USB keyboard device */
     std::string keyboardPath;
     /* @brief Path to the USB mouse device */