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..cc82c4ca9ba08e1b16a7cdb11af983cdb5646941 100644
--- a/cc/resources/video_resource_updater_unittest.cc
+++ b/cc/resources/video_resource_updater_unittest.cc
@@ -504,5 +504,52 @@ 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];

[danakj, 2016/09/27 20:49:11]

can we name these 2 vars to tell their context a bit more? like

in => integers?
out => half_floats?

That would make the EXPECT_NEAR more clear I think.

[hubbe, 2016/09/27 22:27:36]

Done.

+  unsigned short out[1 << 12];
+  for (int bits = 9; bits <= 12; bits++) {
+    int num_values = 1 << bits;
+    for (int i = 0; i < num_values; i++)
+      in[i] = i;
+
+    VideoResourceUpdater::MakeHalfFloats(in, bits, num_values, out);
+
+    // Multiplier to converting integers to 0.0..1.0 range.
+    float multiplier = 1.0f / (num_values - 1);

[danakj, 2016/09/27 20:49:11]

nit: double (and 1.0 not 1.f) since you're returning double FromHalfFloat?

[hubbe, 2016/09/27 22:27:36]

Done.

+
+    for (int i = 0; i < num_values; i++) {
+      // We expect the result to be within +/- one LSB.

[danakj, 2016/09/27 20:49:11]

nit: can you spell out LSB

[hubbe, 2016/09/27 22:27:36]

Done.

+      // Within the range we care about, half-floats values and
+      // their representation both sort in the same order, so we
+      // can just add one to get the next bigger half-float.
+      float expected_precision =

[danakj, 2016/09/27 20:49:11]

Thanks this is helpful

[hubbe, 2016/09/27 22:27:36]

Done.

+          FromHalfFloat(out[i] + 1) - FromHalfFloat(out[i]);
+      EXPECT_NEAR(FromHalfFloat(out[i]), in[i] * multiplier, expected_precision)
+          << "i = " << i << " bits = " << bits;
+    }
+  }
+}
+
 }  // namespace
 }  // namespace cc