libvpx: Pull from upstream

source/libvpx/y4menc.c

Index: source/libvpx/y4menc.c
===================================================================
--- source/libvpx/y4menc.c	(revision 0)
+++ source/libvpx/y4menc.c	(revision 0)
@@ -0,0 +1,27 @@
+/*
+ *  Copyright (c) 2014 The WebM 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 "./y4menc.h"
+
+int y4m_write_file_header(char *buf, size_t len, int width, int height,
+                          const struct VpxRational *framerate,
+                          vpx_img_fmt_t fmt) {
+  const char *const color = fmt == VPX_IMG_FMT_444A ? "C444alpha\n" :
+                            fmt == VPX_IMG_FMT_I444 ? "C444\n" :
+                            fmt == VPX_IMG_FMT_I422 ? "C422\n" :
+                            "C420jpeg\n";
+
+  return snprintf(buf, len, "YUV4MPEG2 W%u H%u F%u:%u I%c %s", width, height,
+                  framerate->numerator, framerate->denominator, 'p', color);
+}
+
+int y4m_write_frame_header(char *buf, size_t len) {
+  return snprintf(buf, len, "FRAME\n");
+}