diff -up chromium-67.0.3396.48/content/renderer/media/webrtc/peer_connection_dependency_factory.cc.ffmpeg33 chromium-67.0.3396.48/content/renderer/media/webrtc/peer_connection_dependency_factory.cc
--- chromium-67.0.3396.48/content/renderer/media/webrtc/peer_connection_dependency_factory.cc.ffmpeg33	2018-05-21 13:00:57.484186164 +0200
+++ chromium-67.0.3396.48/content/renderer/media/webrtc/peer_connection_dependency_factory.cc	2018-05-21 13:00:10.844131078 +0200
@@ -52,6 +52,7 @@
 #include "crypto/openssl_util.h"
 #include "jingle/glue/thread_wrapper.h"
 #include "media/base/media_permission.h"
+#include "media/filters/ffmpeg_glue.h"
 #include "media/media_buildflags.h"
 #include "media/video/gpu_video_accelerator_factories.h"
 #include "third_party/blink/public/platform/web_media_constraints.h"
@@ -158,8 +159,12 @@ void PeerConnectionDependencyFactory::Cr
 
 #if BUILDFLAG(RTC_USE_H264) && BUILDFLAG(ENABLE_FFMPEG_VIDEO_DECODERS)
   // Building /w |rtc_use_h264|, is the corresponding run-time feature enabled?
-  if (!base::FeatureList::IsEnabled(kWebRtcH264WithOpenH264FFmpeg)) {
-    // Feature is to be disabled.
+  if (base::FeatureList::IsEnabled(kWebRtcH264WithOpenH264FFmpeg)) {
+    // |H264DecoderImpl| may be used which depends on FFmpeg, therefore we need
+    // to initialize FFmpeg before going further.
+    media::FFmpegGlue::InitializeFFmpeg();
+  } else {
+    // Feature is to be disabled, no need to make sure FFmpeg is initialized.
     webrtc::DisableRtcUseH264();
   }
 #else
diff -up chromium-67.0.3396.48/media/cdm/library_cdm/clear_key_cdm/clear_key_cdm.cc.ffmpeg33 chromium-67.0.3396.48/media/cdm/library_cdm/clear_key_cdm/clear_key_cdm.cc
--- chromium-67.0.3396.48/media/cdm/library_cdm/clear_key_cdm/clear_key_cdm.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/cdm/library_cdm/clear_key_cdm/clear_key_cdm.cc	2018-05-21 13:00:10.844131078 +0200
@@ -38,6 +38,14 @@
 #include "media/base/media.h"
 #include "media/cdm/library_cdm/clear_key_cdm/ffmpeg_cdm_audio_decoder.h"
 
+// Include FFmpeg avformat.h for av_register_all().
+extern "C" {
+// Temporarily disable possible loss of data warning.
+MSVC_PUSH_DISABLE_WARNING(4244);
+#include <libavformat/avformat.h>
+MSVC_POP_WARNING();
+}  // extern "C"
+
 #if !defined COMPONENT_BUILD
 static base::AtExitManager g_at_exit_manager;
 #endif
@@ -226,6 +234,7 @@ void INITIALIZE_CDM_MODULE() {
   DVLOG(1) << __func__;
 #if defined(CLEAR_KEY_CDM_USE_FFMPEG_DECODER)
   media::InitializeMediaLibrary();
+  av_register_all();
 #endif  // CLEAR_KEY_CDM_USE_FFMPEG_DECODER
 
   g_is_cdm_module_initialized = true;
diff -up chromium-67.0.3396.48/media/ffmpeg/ffmpeg_common_unittest.cc.ffmpeg33 chromium-67.0.3396.48/media/ffmpeg/ffmpeg_common_unittest.cc
--- chromium-67.0.3396.48/media/ffmpeg/ffmpeg_common_unittest.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/ffmpeg/ffmpeg_common_unittest.cc	2018-05-21 13:00:10.844131078 +0200
@@ -25,7 +25,9 @@ namespace media {
 
 class FFmpegCommonTest : public testing::Test {
  public:
-  FFmpegCommonTest() {}
+  FFmpegCommonTest() {
+    FFmpegGlue::InitializeFFmpeg();
+  }
   ~FFmpegCommonTest() override = default;
 };
 
diff -up chromium-67.0.3396.48/media/filters/ffmpeg_audio_decoder.cc.ffmpeg33 chromium-67.0.3396.48/media/filters/ffmpeg_audio_decoder.cc
--- chromium-67.0.3396.48/media/filters/ffmpeg_audio_decoder.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/filters/ffmpeg_audio_decoder.cc	2018-05-21 13:00:10.844131078 +0200
@@ -80,6 +80,8 @@ void FFmpegAudioDecoder::Initialize(
     return;
   }
 
+  FFmpegGlue::InitializeFFmpeg();
+
   if (!ConfigureDecoder(config)) {
     av_sample_format_ = 0;
     bound_init_cb.Run(false);
diff -up chromium-67.0.3396.48/media/filters/ffmpeg_glue.cc.ffmpeg33 chromium-67.0.3396.48/media/filters/ffmpeg_glue.cc
--- chromium-67.0.3396.48/media/filters/ffmpeg_glue.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/filters/ffmpeg_glue.cc	2018-05-21 13:00:10.844131078 +0200
@@ -63,7 +63,13 @@ static int64_t AVIOSeekOperation(void* o
   return new_offset;
 }
 
+void FFmpegGlue::InitializeFFmpeg() {
+  av_register_all();
+}
+
 FFmpegGlue::FFmpegGlue(FFmpegURLProtocol* protocol) {
+  InitializeFFmpeg();
+
   // Initialize an AVIOContext using our custom read and seek operations.  Don't
   // keep pointers to the buffer since FFmpeg may reallocate it on the fly.  It
   // will be cleaned up
diff -up chromium-67.0.3396.48/media/filters/ffmpeg_glue.h.ffmpeg33 chromium-67.0.3396.48/media/filters/ffmpeg_glue.h
--- chromium-67.0.3396.48/media/filters/ffmpeg_glue.h.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/filters/ffmpeg_glue.h	2018-05-21 13:00:10.844131078 +0200
@@ -17,6 +17,10 @@
 //
 // The glue in turn processes those read and seek requests using the
 // FFmpegURLProtocol provided during construction.
+//
+// FFmpegGlue is also responsible for initializing FFmpeg, which is done once
+// per process.  Initialization includes: turning off log messages, registering
+// a lock manager, and finally registering all demuxers and codecs.
 
 #ifndef MEDIA_FILTERS_FFMPEG_GLUE_H_
 #define MEDIA_FILTERS_FFMPEG_GLUE_H_
@@ -59,6 +63,8 @@ class MEDIA_EXPORT FFmpegURLProtocol {
 
 class MEDIA_EXPORT FFmpegGlue {
  public:
+  static void InitializeFFmpeg();
+
   // See file documentation for usage.  |protocol| must outlive FFmpegGlue.
   explicit FFmpegGlue(FFmpegURLProtocol* protocol);
   ~FFmpegGlue();
diff -up chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder.cc.ffmpeg33 chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder.cc
--- chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder.cc	2018-05-21 13:00:10.844131078 +0200
@@ -28,6 +28,7 @@
 #include "media/base/video_util.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 #include "media/ffmpeg/ffmpeg_decoding_loop.h"
+#include "media/filters/ffmpeg_glue.h"
 
 namespace media {
 
@@ -110,6 +111,7 @@ static void ReleaseVideoBufferImpl(void*
 
 // static
 bool FFmpegVideoDecoder::IsCodecSupported(VideoCodec codec) {
+  FFmpegGlue::InitializeFFmpeg();
   return avcodec_find_decoder(VideoCodecToCodecID(codec)) != nullptr;
 }
 
@@ -252,6 +254,8 @@ void FFmpegVideoDecoder::Initialize(
     return;
   }
 
+  FFmpegGlue::InitializeFFmpeg();
+
   if (!ConfigureDecoder(config, low_delay)) {
     bound_init_cb.Run(false);
     return;
diff -up chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder_unittest.cc.ffmpeg33 chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder_unittest.cc
--- chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder_unittest.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/filters/ffmpeg_video_decoder_unittest.cc	2018-05-21 13:00:10.844131078 +0200
@@ -29,6 +29,7 @@
 #include "media/base/video_frame.h"
 #include "media/base/video_util.h"
 #include "media/ffmpeg/ffmpeg_common.h"
+#include "media/filters/ffmpeg_glue.h"
 #include "media/filters/ffmpeg_video_decoder.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
@@ -62,6 +63,8 @@ class FFmpegVideoDecoderTest : public te
       : decoder_(new FFmpegVideoDecoder(&media_log_)),
         decode_cb_(base::Bind(&FFmpegVideoDecoderTest::DecodeDone,
                               base::Unretained(this))) {
+    FFmpegGlue::InitializeFFmpeg();
+
     // Initialize various test buffers.
     frame_buffer_.reset(new uint8_t[kCodedSize.GetArea()]);
     end_of_stream_buffer_ = DecoderBuffer::CreateEOSBuffer();
diff -up chromium-67.0.3396.48/media/gpu/video_encode_accelerator_unittest.cc.ffmpeg33 chromium-67.0.3396.48/media/gpu/video_encode_accelerator_unittest.cc
--- chromium-67.0.3396.48/media/gpu/video_encode_accelerator_unittest.cc.ffmpeg33	2018-05-21 12:59:42.884097603 +0200
+++ chromium-67.0.3396.48/media/gpu/video_encode_accelerator_unittest.cc	2018-05-21 13:00:10.844131078 +0200
@@ -44,6 +44,7 @@
 #include "media/base/test_data_util.h"
 #include "media/base/video_decoder.h"
 #include "media/base/video_frame.h"
+#include "media/filters/ffmpeg_glue.h"
 #include "media/filters/ffmpeg_video_decoder.h"
 #include "media/filters/ivf_parser.h"
 #include "media/gpu/buildflags.h"
@@ -784,6 +785,7 @@ VideoFrameQualityValidator::VideoFrameQu
 void VideoFrameQualityValidator::Initialize(const gfx::Size& coded_size,
                                             const gfx::Rect& visible_size) {
   DCHECK(thread_checker_.CalledOnValidThread());
+  FFmpegGlue::InitializeFFmpeg();
 
   gfx::Size natural_size(visible_size.size());
   // The default output format of ffmpeg video decoder is YV12.