avutil/frame: Add a flag to discard frame after decode.

Signed-off-by: Sasi Inguva <isasi@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/frame.h

@@ -395,6 +395,10 @@ typedef struct AVFrame {
  * The frame data may be corrupted, e.g. due to decoding errors.
  */
 #define AV_FRAME_FLAG_CORRUPT       (1 << 0)
+/**
+ * A flag to mark the frames which need to be decoded, but shouldn't be output.
+ */
+#define AV_FRAME_FLAG_DISCARD   (1 << 2)
 /**
  * @}
  */