Multiframe quality enhancement postprocessing

Adds a multiframe postprocessing module to enhance the quality of
certain frames that are coded at lower quality than preceding frames.
The module can be invoked from the commandline by use of the --mfqe
option, and will be most beneficial for enhancing the quality of
frames decoded using scalable patterns.

Uses the vp8_variance_var16x16 and vp8_variance_sad16x16 function
pointers to compute SAD and Variance of blocks.

Change-Id: Id73d2a6e3572d07f9f8e36bbce00a4fc5ffd8961

vpxdec.c

diff --git a/vpxdec.c b/vpxdec.c
index 7401101..4482f3d 100644
--- a/vpxdec.c
+++ b/vpxdec.c
@@ -124,11 +124,13 @@
                                        "Display only selected block modes");
 static const arg_def_t pp_disp_mvs = ARG_DEF(NULL, "pp-dbg-mvs", 1,
                                        "Draw only selected motion vectors");
+static const arg_def_t mfqe = ARG_DEF(NULL, "mfqe", 0,
+                                       "Enable multiframe quality enhancement");
 
 static const arg_def_t *vp8_pp_args[] =
 {
     &addnoise_level, &deblock, &demacroblock_level, &pp_debug_info,
-    &pp_disp_ref_frame, &pp_disp_mb_modes, &pp_disp_b_modes, &pp_disp_mvs,
+    &pp_disp_ref_frame, &pp_disp_mb_modes, &pp_disp_b_modes, &pp_disp_mvs, &mfqe,
     NULL
 };
 #endif
@@ -803,6 +805,11 @@
             postproc = 1;
             vp8_pp_cfg.post_proc_flag |= VP8_DEBLOCK;
         }
+        else if (arg_match(&arg, &mfqe, argi))
+        {
+            postproc = 1;
+            vp8_pp_cfg.post_proc_flag |= VP8_MFQE;
+        }
         else if (arg_match(&arg, &pp_debug_info, argi))
         {
             unsigned int level = arg_parse_uint(&arg);