diff --git a/tools/generate_stubs/generate_stubs.py b/tools/generate_stubs/generate_stubs.py
index 7d2f91b8b6787..141a608b995eb 100755
--- a/tools/generate_stubs/generate_stubs.py
+++ b/tools/generate_stubs/generate_stubs.py
@@ -382,7 +382,7 @@ def ExtractModuleName(infile_path):
   return basename
 
 
-def ParseSignatures(infile):
+def ParseSignaturesReal(infile):
   """Parses function signatures in the input file.
 
   This function parses a file of signatures into a list of dictionaries that
@@ -426,6 +426,27 @@ def ParseSignatures(infile):
   return signatures
 
 
+# Sometimes additional signatures other than what is exposed to Chromium are
+# needed, in particular for ffmpeg. If we ever make a fork of ffmpeg, is
+# probably a good idea to remove this patch and add the signatures directly on
+# the .sigs file at the dependency repository. In order to expose additional
+# signatures of a library foobar, just add a .sig file prefixed with "xwalk_" at
+# the root folder of the directory containing this script.
+def ParseSignatures(infile):
+  signatures = ParseSignaturesReal(infile)
+
+  xwalk_sig_dir = os.path.dirname(os.path.realpath(__file__))
+  xwalk_sig_file = os.path.join(xwalk_sig_dir,
+                                'xwalk_' + os.path.basename(infile.name))
+
+  if os.path.exists(xwalk_sig_file):
+    xwalk_infile = open(xwalk_sig_file, 'r')
+    signatures += ParseSignaturesReal(xwalk_infile)
+    xwalk_infile.close()
+
+  return signatures
+
+
 def WriteWindowsDefFile(module_name, signatures, outfile):
   """Writes a windows def file to the given output file object.
 
diff --git a/tools/generate_stubs/xwalk_ffmpegsumo.sigs b/tools/generate_stubs/xwalk_ffmpegsumo.sigs
new file mode 100644
index 0000000000000..ab8f2f940360a
--- /dev/null
+++ b/tools/generate_stubs/xwalk_ffmpegsumo.sigs
@@ -0,0 +1,7 @@
+# Copyright (c) 2013 Intel Corporation. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+AVCodec *av_codec_next(const AVCodec *c);
+int av_codec_is_encoder(const AVCodec *c);
+int av_codec_is_decoder(const AVCodec *c);