Add -D_WIN32_WINNT=0x0601 flag to target Windows 7
Also document that Visual Studio 2015 (14.0) is required for Visual
Studio build.
BUG=aomedia:2242
Change-Id: I043b327cd47f1a77ad07886c5501ef65b3350934
diff --git a/README.md b/README.md
index cab3f99..6b58d35 100644
--- a/README.md
+++ b/README.md
@@ -210,15 +210,18 @@
### Microsoft Visual Studio builds
-Building the AV1 codec library in Microsoft Visual Studio is supported. The
-following example demonstrates generating projects and a solution for the
-Microsoft IDE:
+Building the AV1 codec library in Microsoft Visual Studio is supported. Visual
+Studio 2015 (14.0) or later is required. The following example demonstrates
+generating projects and a solution for the Microsoft IDE:
~~~
# This does not require a bash shell; command.exe is fine.
$ cmake path/to/aom -G "Visual Studio 15 2017"
~~~
+NOTE: The build system targets Windows 7 or later by compiling files with
+`-D_WIN32_WINNT=0x0601`.
+
### Xcode builds
Building the AV1 codec library in Xcode is supported. The following example
