12-bit vp9 video support

cc/resources/video_resource_updater_unittest.cc

Index: cc/resources/video_resource_updater_unittest.cc
diff --git a/cc/resources/video_resource_updater_unittest.cc b/cc/resources/video_resource_updater_unittest.cc
index 938c0fc546bdcaef7301b99a822963244e29274a..90e1c0320b0cd3567fbba805f683d04b13a12817 100644
--- a/cc/resources/video_resource_updater_unittest.cc
+++ b/cc/resources/video_resource_updater_unittest.cc
@@ -504,5 +504,46 @@ TEST_F(VideoResourceUpdaterTest, CreateForHardwarePlanes_StreamTexture) {
   EXPECT_FALSE(context3d_->WasImmutableTextureCreated());
 }
 
+namespace {
+
+// Convert an IEEE 754 half-float to a double value
+// that we can do math on.
+double FromHalfFloat(uint16_t half_float) {
+  if (!half_float)
+    return 0.0;
+  int sign = (half_float & 0x8000) ? -1 : 1;
+  int exponent = (half_float >> 10) & 0x1F;
+  int fraction = half_float & 0x3FF;
+  if (exponent == 0) {
+    return pow(2.0, -24.0) * fraction;
+  } else if (exponent == 0x1F) {
+    return sign * 1000000000000.0;
+  } else {
+    return pow(2.0, exponent - 25) * (0x400 + fraction);
+  }
+}
+
+}  // namespace
+
+TEST_F(VideoResourceUpdaterTest, MakeHalfFloatTest) {
+  unsigned short in[1 << 12];
+  unsigned short out[1 << 12];
+  for (int bits = 9; bits <= 12; bits++) {
+    size_t num_values = 1 << bits;
+    for (size_t i = 0; i < num_values; i++)
+      in[i] = i;
+
+    float mult = 1.0f / (num_values - 1);

[danakj, 2016/09/26 22:10:39]

Why this mult?

[hubbe, 2016/09/27 00:03:25]

Is "multiplier" better? Or did I misunderstand the question?

[danakj, 2016/09/27 00:15:58]

I was wondering why 1/(n-1)?

[hubbe, 2016/09/27 00:31:24]

Ah. I did add a comment for that.

+
+    VideoResourceUpdater::MakeHalfFloats(in, mult, num_values, out);
+
+    for (size_t i = 0; i < num_values; i++) {
+      EXPECT_NEAR(FromHalfFloat(out[i]), in[i] * mult,
+                  FromHalfFloat(out[i] + 1) - FromHalfFloat(out[i]))

[danakj, 2016/09/26 22:10:39]

What does +1 on a half-float do to it? Can you leave a comment

[hubbe, 2016/09/27 00:03:25]

Done.

+          << "i = " << i << " bits = " << bits;
+    }
+  }
+}
+
 }  // namespace
 }  // namespace cc