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_video.hpp b/ikvm_video.hpp
index fb8c5da..23c58a7 100644
--- a/ikvm_video.hpp
+++ b/ikvm_video.hpp
@@ -23,7 +23,7 @@
      * @param[in] input - Reference to the Input object
      * @param[in] fr    - desired frame rate of the video
      */
-    Video(const std::string& p, Input& input, int fr = 30);
+    Video(const std::string& p, Input& input, int fr = 30, int sub = 0);
     ~Video();
     Video(const Video&) = default;
     Video& operator=(const Video&) = default;
@@ -93,6 +93,24 @@
     {
         return width;
     }
+    /*
+     * @brief Gets the subsampling of the video frame
+     *
+     * @return Value of the subsampling of video frame, 1:420/0:444
+     */
+    inline int getSubsampling() const
+    {
+        return subSampling;
+    }
+    /*
+     * @brief Sets the subsampling of the video frame
+     *
+     * @return Value of the subsampling of video frame, 1:420/0:444
+     */
+    inline void setSubsampling(int _sub)
+    {
+        subSampling = _sub;
+    }
 
     /* @brief Number of bits per component of a pixel */
     static const int bitsPerSample;
@@ -141,6 +159,8 @@
     size_t height;
     /* @brief Width in pixels of the video frame */
     size_t width;
+    /* @brief jpeg's subsampling, 1:420/0:444 */
+    int subSampling;
     /* @brief Reference to the Input object */
     Input& input;
     /* @brief Path to the V4L2 video device */