Add media::GetFormatDescriptionColorSpace

This function is nearly identical to media::GetImageBufferColorSpace,
but instead operates on a CMFormatDescriptionRef.

Add DCHECKs that the behavior of the two functions be the same, that is,
the kCVImageBuffer-prefixed and  kCMFormatDescription-prefixed
constants be equal.

Use base::mac::CFCast instead of reinterpret_casts.

The next patch in this sequence will move these two functions over
to media/base/mac, because it will be accessed in capture.

Bug: 959962
Change-Id: I8a4d8468abc866a13cb6181cbd49d9ee04288124
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2436513
Commit-Queue: ccameron <ccameron@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811829}

media/gpu/mac/vt_config_util.h

@@ -26,6 +26,9 @@ CreateFormatExtensions(CMVideoCodecType codec_type,
 MEDIA_GPU_EXPORT gfx::ColorSpace GetImageBufferColorSpace(
     CVImageBufferRef image_buffer);
 
+MEDIA_GPU_EXPORT gfx::ColorSpace GetFormatDescriptionColorSpace(
+    CMFormatDescriptionRef format_description);
+
 }  // namespace media
 
 #endif  // MEDIA_GPU_MAC_VT_CONFIG_UTIL_H_

media/gpu/mac/vt_config_util_unittest.cc

@@ -74,6 +74,34 @@ base::ScopedCFTypeRef<CVImageBufferRef> CreateCVImageBuffer(
   return image_buffer;
 }
 
+base::ScopedCFTypeRef<CMFormatDescriptionRef> CreateFormatDescription(
+    CFStringRef primaries,
+    CFStringRef transfer,
+    CFStringRef matrix) {
+  base::ScopedCFTypeRef<CFMutableDictionaryRef> extensions(
+      CFDictionaryCreateMutable(kCFAllocatorDefault, 0,
+                                &kCFTypeDictionaryKeyCallBacks,
+                                &kCFTypeDictionaryValueCallBacks));
+
+  if (primaries) {
+    CFDictionarySetValue(
+        extensions, kCMFormatDescriptionExtension_ColorPrimaries, primaries);
+  }
+  if (transfer) {
+    CFDictionarySetValue(
+        extensions, kCMFormatDescriptionExtension_TransferFunction, transfer);
+  }
+  if (matrix) {
+    CFDictionarySetValue(extensions, kCMFormatDescriptionExtension_YCbCrMatrix,
+                         matrix);
+  }
+  base::ScopedCFTypeRef<CMFormatDescriptionRef> result;
+  CMFormatDescriptionCreate(nullptr, kCMMediaType_Video,
+                            kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange,
+                            extensions.get(), result.InitializeInto());
+  return result;
+}
+
 gfx::ColorSpace ToBT709_APPLE(gfx::ColorSpace cs) {
   return gfx::ColorSpace(cs.GetPrimaryID(),
                          gfx::ColorSpace::TransferID::BT709_APPLE,
@@ -364,4 +392,22 @@ TEST(VTConfigUtil, GetImageBufferColorSpace_BT2020_HLG) {
   }
 }
 
+TEST(VTConfigUtil, FormatDescriptionInvalid) {
+  auto format_descriptor =
+      CreateFormatDescription(CFSTR("Cows"), CFSTR("Go"), CFSTR("Moo"));
+  ASSERT_TRUE(format_descriptor);
+  auto cs = GetFormatDescriptionColorSpace(format_descriptor);
+  EXPECT_EQ(gfx::ColorSpace::CreateREC709(), cs);
+}
+
+TEST(VTConfigUtil, FormatDescriptionBT709) {
+  auto format_descriptor =
+      CreateFormatDescription(kCMFormatDescriptionColorPrimaries_ITU_R_709_2,
+                              kCMFormatDescriptionTransferFunction_ITU_R_709_2,
+                              kCMFormatDescriptionYCbCrMatrix_ITU_R_709_2);
+  ASSERT_TRUE(format_descriptor);
+  auto cs = GetFormatDescriptionColorSpace(format_descriptor);
+  EXPECT_EQ(ToBT709_APPLE(gfx::ColorSpace::CreateREC709()), cs);
+}
+
 }  // namespace media