From 4c84adf2f52d64c32f7d86eca9d8f4988e990292 Mon Sep 17 00:00:00 2001
From: Jan Grulich <jgrulich@redhat.com>
Date: Mon, 23 Jan 2023 09:30:48 +0100
Subject: [WebRTC] Video encoding: allow to dlopen h264


diff --git a/third_party/webrtc/modules/video_coding/BUILD.gn b/third_party/webrtc/modules/video_coding/BUILD.gn
index 77f2daf3e..b1b4945b9 100644
--- a/third_party/webrtc/modules/video_coding/BUILD.gn
+++ b/third_party/webrtc/modules/video_coding/BUILD.gn
@@ -7,6 +7,7 @@
 # be found in the AUTHORS file in the root of the source tree.

 import("//third_party/libaom/options.gni")
+import("//tools/generate_stubs/rules.gni")
 import("../../webrtc.gni")

 rtc_library("encoded_frame") {
@@ -499,6 +500,21 @@ rtc_library("video_coding_utility") {
   ]
 }

+if (rtc_use_h264 && rtc_dlopen_openh264) {
+  # When OpenH264 is not directly linked, use stubs to allow for dlopening of
+  # the binary.
+  generate_stubs("openh264_stubs") {
+    configs = [ "../../:common_config" ]
+    deps = [ "../../rtc_base" ]
+    extra_header = "codecs/h264/openh264_stub_header.fragment"
+    logging_function = "RTC_LOG(LS_VERBOSE)"
+    logging_include = "rtc_base/logging.h"
+    output_name = "codecs/h264/openh264_stubs"
+    path_from_source = "modules/video_coding/codecs/h264"
+    sigs = [ "codecs/h264/openh264.sigs" ]
+  }
+}
+
 rtc_library("webrtc_h264") {
   visibility = [ "*" ]
   sources = [
@@ -542,11 +558,18 @@ rtc_library("webrtc_h264") {
   ]

   if (rtc_use_h264) {
-    deps += [
-      "//third_party/ffmpeg",
-      "//third_party/openh264:buildflags",
-      "//third_party/openh264:encoder",
-    ]
+    deps += [ "//third_party/ffmpeg" ]
+
+    if (rtc_dlopen_openh264) {
+      defines = [ "WEBRTC_DLOPEN_OPENH264" ]
+      deps += [ ":openh264_stubs" ]
+    } else {
+      deps += [
+        "//third_party/openh264:buildflags",
+        "//third_party/openh264:encoder",
+      ]
+    }
+
     if (!build_with_mozilla) {
       deps += [ "../../media:rtc_media_base" ]
     }
diff --git a/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc b/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
index 5029dc9..e5b878e 100644
--- a/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
+++ b/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc
@@ -31,24 +31,27 @@
 #include "system_wrappers/include/metrics.h"
 #include "third_party/libyuv/include/libyuv/convert.h"
 #include "third_party/libyuv/include/libyuv/scale.h"
-// TODO(crbug.com/1218384): Remove after new openh264 is rolled.
-#include "third_party/openh264/buildflags.h"
-#if BUILDFLAG(OPENH264_API_WELS)
 #include "third_party/openh264/src/codec/api/wels/codec_api.h"
 #include "third_party/openh264/src/codec/api/wels/codec_app_def.h"
 #include "third_party/openh264/src/codec/api/wels/codec_def.h"
 #include "third_party/openh264/src/codec/api/wels/codec_ver.h"
-#else
-#include "third_party/openh264/src/codec/api/svc/codec_api.h"
-#include "third_party/openh264/src/codec/api/svc/codec_app_def.h"
-#include "third_party/openh264/src/codec/api/svc/codec_def.h"
-#include "third_party/openh264/src/codec/api/svc/codec_ver.h"
-#endif
+
+#if defined(WEBRTC_DLOPEN_OPENH264)
+#include "modules/video_coding/codecs/h264/openh264_stubs.h"
+#endif  // defined(WEBRTC_DLOPEN_OPENH264)

 namespace webrtc {

 namespace {

+#if defined(WEBRTC_DLOPEN_OPENH264)
+using modules_video_coding_codecs_h264::InitializeStubs;
+using modules_video_coding_codecs_h264::kModuleOpenh264;
+using modules_video_coding_codecs_h264::StubPathMap;
+
+static constexpr char kOpenH264Lib[] = "libopenh264.so.7";
+#endif
+
 const bool kOpenH264EncoderDetailedLogging = false;

 // QP scaling thresholds.
@@ -176,6 +179,15 @@ H264EncoderImpl::~H264EncoderImpl() {

 int32_t H264EncoderImpl::InitEncode(const VideoCodec* inst,
                                     const VideoEncoder::Settings& settings) {
+#if defined(WEBRTC_DLOPEN_OPENH264)
+  StubPathMap paths;
+  paths[kModuleOpenh264].push_back(kOpenH264Lib);
+
+  static bool result = InitializeStubs(paths);
+  if (!result)
+    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
+#endif
+
   ReportInit();
   if (!inst || inst->codecType != kVideoCodecH264) {
     ReportError();
diff --git a/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.h b/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.h
index c1d8191..bf70c89 100644
--- a/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.h
+++ b/third_party/webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.h
@@ -30,13 +30,7 @@
 #include "modules/video_coding/codecs/h264/include/h264.h"
 #include "modules/video_coding/svc/scalable_video_controller.h"
 #include "modules/video_coding/utility/quality_scaler.h"
-// TODO(crbug.com/1218384): Remove after new openh264 is rolled.
-#include "third_party/openh264/buildflags.h"
-#if BUILDFLAG(OPENH264_API_WELS)
 #include "third_party/openh264/src/codec/api/wels/codec_app_def.h"
-#else
-#include "third_party/openh264/src/codec/api/svc/codec_app_def.h"
-#endif

 class ISVCEncoder;

diff --git a/third_party/webrtc/modules/video_coding/codecs/h264/openh264.sigs b/third_party/webrtc/modules/video_coding/codecs/h264/openh264.sigs
new file mode 100644
index 000000000..4924f8e9a
--- /dev/null
+++ b/third_party/webrtc/modules/video_coding/codecs/h264/openh264.sigs
@@ -0,0 +1,14 @@
+// Copyright 2022 The WebRTC 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.
+
+//------------------------------------------------
+// Functions from OpenH264.
+//------------------------------------------------
+int WelsCreateSVCEncoder(ISVCEncoder **ppEncoder);
+void WelsDestroySVCEncoder(ISVCEncoder *pEncoder);
+int WelsGetDecoderCapability(SDecoderCapability *pDecCapability);
+long WelsCreateDecoder(ISVCDecoder **ppDecoder);
+void WelsDestroyDecoder(ISVCDecoder *pDecoder);
+OpenH264Version WelsGetCodecVersion(void);
+void WelsGetCodecVersionEx(OpenH264Version *pVersion);
diff --git a/third_party/webrtc/modules/video_coding/codecs/h264/openh264_stub_header.fragment b/third_party/webrtc/modules/video_coding/codecs/h264/openh264_stub_header.fragment
new file mode 100644
index 000000000..9bc0a7cbe
--- /dev/null
+++ b/third_party/webrtc/modules/video_coding/codecs/h264/openh264_stub_header.fragment
@@ -0,0 +1,11 @@
+// The extra include header needed in the generated stub file for defining
+// various OpenH264 types.
+
+extern "C" {
+
+#include "third_party/openh264/src/codec/api/wels/codec_api.h"
+#include "third_party/openh264/src/codec/api/wels/codec_app_def.h"
+#include "third_party/openh264/src/codec/api/wels/codec_def.h"
+#include "third_party/openh264/src/codec/api/wels/codec_ver.h"
+
+}
diff --git a/third_party/webrtc/webrtc.gni b/third_party/webrtc/webrtc.gni
index a5da76c6f..6da346fd4 100644
--- a/third_party/webrtc/webrtc.gni
+++ b/third_party/webrtc/webrtc.gni
@@ -177,6 +177,10 @@ declare_args() {
   rtc_use_h264 =
       proprietary_codecs && !is_android && !is_ios && !(is_win && !is_clang)
 
+  # Allow to use OpenH264 on systems where OpenH264 cannot be installed by
+  # default due to licensing, but can be installed later from other sources.
+  rtc_dlopen_openh264 = false
+
   # Enable this flag to make webrtc::Mutex be implemented by absl::Mutex.
   rtc_use_absl_mutex = false