Look into full URL spec to see whether it is MP4

media/base/mime_util_internal.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/base/mime_util_internal.h"
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ skipping 583 matching lines @@
       // MediaPlayer does not support Opus in ogg containers.
       if (base::EndsWith(mime_type_lower_case, "ogg",
                          base::CompareCase::SENSITIVE)) {
         return false;
       }
 
       DCHECK(!is_encrypted || platform_info.has_platform_decoders);
       return true;
 
     case H264:
-      // The unified pipeline requires platform support for h264.
-      if (platform_info.is_unified_media_pipeline_enabled)
-        return platform_info.has_platform_decoders;
-
-      // When MediaPlayer or MediaCodec is used, h264 is always supported.
-      DCHECK(!is_encrypted || platform_info.has_platform_decoders);
-      return true;
+      // When content is not encrypted we fall back to MediaPlayer, thus we
+      // always support H264. For EME we need MediaCodec.
+      return !is_encrypted || platform_info.has_platform_decoders;
 
     case HEVC:
 #if BUILDFLAG(ENABLE_HEVC_DEMUXING)
       if (platform_info.is_unified_media_pipeline_enabled &&
           !platform_info.has_platform_decoders) {
         return false;
       }
 
 #if defined(OS_ANDROID)
       // HEVC/H.265 is supported in Lollipop+ (API Level 21), according to
@@ skipping 182 matching lines @@
     const std::string& mime_type_lower_case,
     bool is_encrypted) const {
   Codec default_codec = Codec::INVALID_CODEC;
   if (!GetDefaultCodecLowerCase(mime_type_lower_case, &default_codec))
     return false;
   return IsCodecSupported(default_codec, mime_type_lower_case, is_encrypted);
 }
 
 }  // namespace internal
 }  // namespace media