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/build_overrides/build.gni

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+# Copyright 2016 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.
+
+# Variable that can be used to support multiple build scenarios, like having
+# Chromium specific targets in a client project's GN file etc.
+build_with_chromium = false
+
+# Some non-Chromium builds don't support building java targets.
+enable_java_templates = true
+
+# Allow using custom suppressions files (currently not used by libyuv).
+asan_suppressions_file = "//build/sanitizers/asan_suppressions.cc"
+lsan_suppressions_file = "//build/sanitizers/lsan_suppressions.cc"
+tsan_suppressions_file = "//build/sanitizers/tsan_suppressions.cc"
+
+msan_blacklist_path =
+    rebase_path("//tools_libyuv/msan/blacklist.txt", root_build_dir)
+ubsan_blacklist_path =
+    rebase_path("//tools_libyuv/ubsan/blacklist.txt", root_build_dir)
+ubsan_vptr_blacklist_path =
+    rebase_path("//tools_libyuv/ubsan/vptr_blacklist.txt", root_build_dir)
+
+# For Chromium, Android 32-bit non-component, non-clang builds hit a 4GiB size
+# limit, making them requiring symbol_level=2. WebRTC doesn't hit that problem
+# so we just ignore that assert. See https://crbug.com/648948 for more info.
+ignore_elf32_limitations = true
+
+# Use bundled hermetic Xcode installation maintained by Chromium,
+# except for local iOS builds where it is unsupported.
+if (host_os == "mac") {
+  _result = exec_script("//build/mac/should_use_hermetic_xcode.py",
+                        [ target_os ],
+                        "value")
+  assert(_result != 2,
+         "Do not allow building targets with the default" +
+             "hermetic toolchain if the minimum OS version is not met.")
+  use_system_xcode = _result == 0
+}
+
+declare_args() {
+  # Tracing support requires //third_party/perfetto.
+  enable_base_tracing = false
+  use_perfetto_client_library = false
+
+  # Allows googletest to pretty-print various absl types.
+  # Defined here rather than in gtest.gni to match chromium.
+  gtest_enable_absl_printers = true
+}

thirdparty/libyuv/build_overrides/gtest.gni

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+# Copyright (c) 2016 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.
+
+# Include support for registering main function in multi-process tests.
+gtest_include_multiprocess = true
+
+# Include support for platform-specific operations across unit tests.
+gtest_include_platform_test = true
+
+# Exclude support for testing Objective C code on OS X and iOS.
+gtest_include_objc_support = true
+
+# Exclude support for flushing coverage files on iOS.
+gtest_include_ios_coverage = true