{aq_variance,firstpass,ratectrl}.c: quiet -Wshorten warnings

ported from libvpx:

Added casts to remove warnings:

In regards to the safety of these casts they are of two types:-

- Normalized bits per (16x16) MB stored in a 32 bit int (This is safe as
  bits per MB even with << 9 normalization cant overflow 32 bits. Even
  raw 12 bits hdr source even would only be  29 bits :- (4+4+12+9) and
  the encoder imposes much stricter limits than this on max bit rate.

- Cast as part of variance calculations.  There is an internal cast up
  to 64 bit for the Sum X Sum calculation, but after normalization
  dividing by the number of points the result will always be <= the SSE
  value.

BUG=aomedia:445

Change-Id: I4e700236ed83d6b2b1955e92e84c3b1978b9eaa0

av1/encoder/aq_variance.c

@@ -169,8 +169,8 @@ static unsigned int block_variance(const AV1_COMP *const cpi, MACROBLOCK *x,
     aq_variance(x->plane[0].src.buf, x->plane[0].src.stride, av1_all_zeros, 0,
                 bw, bh, &sse, &avg);
 #endif  // CONFIG_HIGHBITDEPTH
-    var = sse - (((int64_t)avg * avg) / (bw * bh));
-    return ((uint64_t)var * 256) / (bw * bh);
+    var = sse - (unsigned int)(((int64_t)avg * avg) / (bw * bh));
+    return (unsigned int)((uint64_t)var * 256) / (bw * bh);
   } else {
 #if CONFIG_HIGHBITDEPTH
     if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {
@@ -185,7 +185,7 @@ static unsigned int block_variance(const AV1_COMP *const cpi, MACROBLOCK *x,
     var = cpi->fn_ptr[bs].vf(x->plane[0].src.buf, x->plane[0].src.stride,
                              av1_all_zeros, 0, &sse);
 #endif  // CONFIG_HIGHBITDEPTH
-    return ((uint64_t)var * 256) >> num_pels_log2_lookup[bs];
+    return (unsigned int)((uint64_t)var * 256) >> num_pels_log2_lookup[bs];
   }
 }
 

av1/encoder/firstpass.c

@@ -1186,7 +1186,8 @@ static int get_twopass_worst_quality(const AV1_COMP *cpi,
     const double speed_term = 1.0 + 0.04 * oxcf->speed;
     double ediv_size_correction;
     const int target_norm_bits_per_mb =
-        ((uint64_t)section_target_bandwidth << BPER_MB_NORMBITS) / active_mbs;
+        (int)((uint64_t)section_target_bandwidth << BPER_MB_NORMBITS) /
+        active_mbs;
     int q;
 
     // Larger image formats are expected to be a little harder to code

av1/encoder/ratectrl.c

@@ -494,7 +494,7 @@ int av1_rc_regulate_q(const AV1_COMP *cpi, int target_bits_per_frame,
   // Calculate required scaling factor based on target frame size and size of
   // frame produced using previous Q.
   target_bits_per_mb =
-      ((uint64_t)target_bits_per_frame << BPER_MB_NORMBITS) / cm->MBs;
+      (int)((uint64_t)target_bits_per_frame << BPER_MB_NORMBITS) / cm->MBs;
 
   i = active_best_quality;
 
@@ -1165,8 +1165,8 @@ void av1_rc_set_frame_target(AV1_COMP *cpi, int target) {
                                   rate_thresh_mult[rc->frame_size_selector]);
 
   // Target rate per SB64 (including partial SB64s.
-  rc->sb64_target_rate =
-      ((int64_t)rc->this_frame_target * 64 * 64) / (cm->width * cm->height);
+  rc->sb64_target_rate = (int)((int64_t)rc->this_frame_target * 64 * 64) /
+                         (cm->width * cm->height);
 }
 
 static void update_alt_ref_frame_stats(AV1_COMP *cpi) {