RGB to YUV conversion using SSE2

This code uses SSE2 intrinsics with the feature of 2x2 subsampling for U and V.
Performance compared to a pure C version is about 20% faster with better
quality.

BUG=None
TEST=None

Review URL: http://codereview.chromium.org/6268018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@73339 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 50 insertions, 0 deletions

diff --git a/media/base/yuv_convert_c.cc b/media/base/yuv_convert_c.cc
new file mode 100644
index 0000000..b5d8345
--- /dev/null
+++ b/media/base/yuv_convert_c.cc
@@ -0,0 +1,50 @@
+// Copyright (c) 2011 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/yuv_convert.h"
+
+namespace media {
+
+static int clip_byte(int x) {
+  if (x > 255)
+    return 255;
+  else if (x < 0)
+    return 0;
+  else
+    return x;
+}
+
+void ConvertRGB32ToYUV(const uint8* rgbframe,
+                       uint8* yplane,
+                       uint8* uplane,
+                       uint8* vplane,
+                       int width,
+                       int height,
+                       int rgbstride,
+                       int ystride,
+                       int uvstride) {
+  for (int i = 0; i < height; ++i) {
+    for (int j = 0; j < width; ++j) {
+      // Since the input pixel format is RGB32, there are 4 bytes per pixel.
+      const uint8* pixel = rgbframe + 4 * j;
+      yplane[j] = clip_byte(((pixel[2] * 66 + pixel[1] * 129 +
+                             pixel[0] * 25 + 128) >> 8) + 16);
+      if (i % 2 == 0 && j % 2 == 0) {
+        uplane[j / 2] = clip_byte(((pixel[2] * -38 + pixel[1] * -74 +
+                                   pixel[0] * 112 + 128) >> 8) + 128);
+        vplane[j / 2] = clip_byte(((pixel[2] * 112 + pixel[1] * -94 +
+                                    pixel[1] * -18 + 128) >> 8) + 128);
+      }
+    }
+
+    rgbframe += rgbstride;
+    yplane += ystride;
+    if (i % 2 == 0) {
+      uplane += uvstride;
+      vplane += uvstride;
+    }
+  }
+}
+
+}  // namespace media