1.Use libyuv instead of ffmpeg to do nv12<->yuv420p convertion;2.Use local package to build libyuv(branch stable 2021.4.28 commit eb6e7bb63738e29efd82ea3cf2a115238a89fa51)

thirdparty/libyuv/download_vs_toolchain.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+#
+# Copyright 2014 The LibYuv Project Authors. All rights reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS. All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+# This script is used to run the vs_toolchain.py script to download the
+# Visual Studio toolchain. It's just a temporary measure while waiting for the
+# Chrome team to move find_depot_tools into src/build to get rid of these
+# workarounds (similar one in gyp_libyuv).
+
+import os
+import sys
+
+
+checkout_root = os.path.dirname(os.path.realpath(__file__))
+sys.path.insert(0, os.path.join(checkout_root, 'build'))
+sys.path.insert(0, os.path.join(checkout_root, 'tools', 'find_depot_tools'))
+
+
+import vs_toolchain  # pylint: disable=wrong-import-position
+
+
+if __name__ == '__main__':
+  sys.exit(vs_toolchain.main())