yuv use a shared table for windows, posix and C...

media/base/yuv_row_posix.cc

 // Copyright (c) 2010 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_row.h"
 
 #ifdef _DEBUG
 #include "base/logging.h"
 #else
 #define DCHECK(a)
 #endif
 
 extern "C" {
-#if USE_MMX
 
-#define RGBY(i) { \
-  static_cast<int16>(1.164 * 64 * (i - 16) + 0.5), \
-  static_cast<int16>(1.164 * 64 * (i - 16) + 0.5), \
-  static_cast<int16>(1.164 * 64 * (i - 16) + 0.5), \
-  0 \
-}
-
-#define RGBU(i) { \
-  static_cast<int16>(2.018 * 64 * (i - 128) + 0.5), \
-  static_cast<int16>(-0.391 * 64 * (i - 128) + 0.5), \
-  0, \
-  static_cast<int16>(256 * 64 - 1) \
-}
-
-#define RGBV(i) { \
-  0, \
-  static_cast<int16>(-0.813 * 64 * (i - 128) + 0.5), \
-  static_cast<int16>(1.596 * 64 * (i - 128) + 0.5), \
-  0 \
-}
-
-#define MMX_ALIGNED(var) var __attribute__((aligned(16)))
-
-
-MMX_ALIGNED(int16 kCoefficientsRgbY[768][4]) = {
-  RGBY(0x00), RGBY(0x01), RGBY(0x02), RGBY(0x03),
-  RGBY(0x04), RGBY(0x05), RGBY(0x06), RGBY(0x07),
-  RGBY(0x08), RGBY(0x09), RGBY(0x0A), RGBY(0x0B),
-  RGBY(0x0C), RGBY(0x0D), RGBY(0x0E), RGBY(0x0F),
-  RGBY(0x10), RGBY(0x11), RGBY(0x12), RGBY(0x13),
-  RGBY(0x14), RGBY(0x15), RGBY(0x16), RGBY(0x17),
-  RGBY(0x18), RGBY(0x19), RGBY(0x1A), RGBY(0x1B),
-  RGBY(0x1C), RGBY(0x1D), RGBY(0x1E), RGBY(0x1F),
-  RGBY(0x20), RGBY(0x21), RGBY(0x22), RGBY(0x23),
-  RGBY(0x24), RGBY(0x25), RGBY(0x26), RGBY(0x27),
-  RGBY(0x28), RGBY(0x29), RGBY(0x2A), RGBY(0x2B),
-  RGBY(0x2C), RGBY(0x2D), RGBY(0x2E), RGBY(0x2F),
-  RGBY(0x30), RGBY(0x31), RGBY(0x32), RGBY(0x33),
-  RGBY(0x34), RGBY(0x35), RGBY(0x36), RGBY(0x37),
-  RGBY(0x38), RGBY(0x39), RGBY(0x3A), RGBY(0x3B),
-  RGBY(0x3C), RGBY(0x3D), RGBY(0x3E), RGBY(0x3F),
-  RGBY(0x40), RGBY(0x41), RGBY(0x42), RGBY(0x43),
-  RGBY(0x44), RGBY(0x45), RGBY(0x46), RGBY(0x47),
-  RGBY(0x48), RGBY(0x49), RGBY(0x4A), RGBY(0x4B),
-  RGBY(0x4C), RGBY(0x4D), RGBY(0x4E), RGBY(0x4F),
-  RGBY(0x50), RGBY(0x51), RGBY(0x52), RGBY(0x53),
-  RGBY(0x54), RGBY(0x55), RGBY(0x56), RGBY(0x57),
-  RGBY(0x58), RGBY(0x59), RGBY(0x5A), RGBY(0x5B),
-  RGBY(0x5C), RGBY(0x5D), RGBY(0x5E), RGBY(0x5F),
-  RGBY(0x60), RGBY(0x61), RGBY(0x62), RGBY(0x63),
-  RGBY(0x64), RGBY(0x65), RGBY(0x66), RGBY(0x67),
-  RGBY(0x68), RGBY(0x69), RGBY(0x6A), RGBY(0x6B),
-  RGBY(0x6C), RGBY(0x6D), RGBY(0x6E), RGBY(0x6F),
-  RGBY(0x70), RGBY(0x71), RGBY(0x72), RGBY(0x73),
-  RGBY(0x74), RGBY(0x75), RGBY(0x76), RGBY(0x77),
-  RGBY(0x78), RGBY(0x79), RGBY(0x7A), RGBY(0x7B),
-  RGBY(0x7C), RGBY(0x7D), RGBY(0x7E), RGBY(0x7F),
-  RGBY(0x80), RGBY(0x81), RGBY(0x82), RGBY(0x83),
-  RGBY(0x84), RGBY(0x85), RGBY(0x86), RGBY(0x87),
-  RGBY(0x88), RGBY(0x89), RGBY(0x8A), RGBY(0x8B),
-  RGBY(0x8C), RGBY(0x8D), RGBY(0x8E), RGBY(0x8F),
-  RGBY(0x90), RGBY(0x91), RGBY(0x92), RGBY(0x93),
-  RGBY(0x94), RGBY(0x95), RGBY(0x96), RGBY(0x97),
-  RGBY(0x98), RGBY(0x99), RGBY(0x9A), RGBY(0x9B),
-  RGBY(0x9C), RGBY(0x9D), RGBY(0x9E), RGBY(0x9F),
-  RGBY(0xA0), RGBY(0xA1), RGBY(0xA2), RGBY(0xA3),
-  RGBY(0xA4), RGBY(0xA5), RGBY(0xA6), RGBY(0xA7),
-  RGBY(0xA8), RGBY(0xA9), RGBY(0xAA), RGBY(0xAB),
-  RGBY(0xAC), RGBY(0xAD), RGBY(0xAE), RGBY(0xAF),
-  RGBY(0xB0), RGBY(0xB1), RGBY(0xB2), RGBY(0xB3),
-  RGBY(0xB4), RGBY(0xB5), RGBY(0xB6), RGBY(0xB7),
-  RGBY(0xB8), RGBY(0xB9), RGBY(0xBA), RGBY(0xBB),
-  RGBY(0xBC), RGBY(0xBD), RGBY(0xBE), RGBY(0xBF),
-  RGBY(0xC0), RGBY(0xC1), RGBY(0xC2), RGBY(0xC3),
-  RGBY(0xC4), RGBY(0xC5), RGBY(0xC6), RGBY(0xC7),
-  RGBY(0xC8), RGBY(0xC9), RGBY(0xCA), RGBY(0xCB),
-  RGBY(0xCC), RGBY(0xCD), RGBY(0xCE), RGBY(0xCF),
-  RGBY(0xD0), RGBY(0xD1), RGBY(0xD2), RGBY(0xD3),
-  RGBY(0xD4), RGBY(0xD5), RGBY(0xD6), RGBY(0xD7),
-  RGBY(0xD8), RGBY(0xD9), RGBY(0xDA), RGBY(0xDB),
-  RGBY(0xDC), RGBY(0xDD), RGBY(0xDE), RGBY(0xDF),
-  RGBY(0xE0), RGBY(0xE1), RGBY(0xE2), RGBY(0xE3),
-  RGBY(0xE4), RGBY(0xE5), RGBY(0xE6), RGBY(0xE7),
-  RGBY(0xE8), RGBY(0xE9), RGBY(0xEA), RGBY(0xEB),
-  RGBY(0xEC), RGBY(0xED), RGBY(0xEE), RGBY(0xEF),
-  RGBY(0xF0), RGBY(0xF1), RGBY(0xF2), RGBY(0xF3),
-  RGBY(0xF4), RGBY(0xF5), RGBY(0xF6), RGBY(0xF7),
-  RGBY(0xF8), RGBY(0xF9), RGBY(0xFA), RGBY(0xFB),
-  RGBY(0xFC), RGBY(0xFD), RGBY(0xFE), RGBY(0xFF),
-
-  // Chroma U table.
-  RGBU(0x00), RGBU(0x01), RGBU(0x02), RGBU(0x03),
-  RGBU(0x04), RGBU(0x05), RGBU(0x06), RGBU(0x07),
-  RGBU(0x08), RGBU(0x09), RGBU(0x0A), RGBU(0x0B),
-  RGBU(0x0C), RGBU(0x0D), RGBU(0x0E), RGBU(0x0F),
-  RGBU(0x10), RGBU(0x11), RGBU(0x12), RGBU(0x13),
-  RGBU(0x14), RGBU(0x15), RGBU(0x16), RGBU(0x17),
-  RGBU(0x18), RGBU(0x19), RGBU(0x1A), RGBU(0x1B),
-  RGBU(0x1C), RGBU(0x1D), RGBU(0x1E), RGBU(0x1F),
-  RGBU(0x20), RGBU(0x21), RGBU(0x22), RGBU(0x23),
-  RGBU(0x24), RGBU(0x25), RGBU(0x26), RGBU(0x27),
-  RGBU(0x28), RGBU(0x29), RGBU(0x2A), RGBU(0x2B),
-  RGBU(0x2C), RGBU(0x2D), RGBU(0x2E), RGBU(0x2F),
-  RGBU(0x30), RGBU(0x31), RGBU(0x32), RGBU(0x33),
-  RGBU(0x34), RGBU(0x35), RGBU(0x36), RGBU(0x37),
-  RGBU(0x38), RGBU(0x39), RGBU(0x3A), RGBU(0x3B),
-  RGBU(0x3C), RGBU(0x3D), RGBU(0x3E), RGBU(0x3F),
-  RGBU(0x40), RGBU(0x41), RGBU(0x42), RGBU(0x43),
-  RGBU(0x44), RGBU(0x45), RGBU(0x46), RGBU(0x47),
-  RGBU(0x48), RGBU(0x49), RGBU(0x4A), RGBU(0x4B),
-  RGBU(0x4C), RGBU(0x4D), RGBU(0x4E), RGBU(0x4F),
-  RGBU(0x50), RGBU(0x51), RGBU(0x52), RGBU(0x53),
-  RGBU(0x54), RGBU(0x55), RGBU(0x56), RGBU(0x57),
-  RGBU(0x58), RGBU(0x59), RGBU(0x5A), RGBU(0x5B),
-  RGBU(0x5C), RGBU(0x5D), RGBU(0x5E), RGBU(0x5F),
-  RGBU(0x60), RGBU(0x61), RGBU(0x62), RGBU(0x63),
-  RGBU(0x64), RGBU(0x65), RGBU(0x66), RGBU(0x67),
-  RGBU(0x68), RGBU(0x69), RGBU(0x6A), RGBU(0x6B),
-  RGBU(0x6C), RGBU(0x6D), RGBU(0x6E), RGBU(0x6F),
-  RGBU(0x70), RGBU(0x71), RGBU(0x72), RGBU(0x73),
-  RGBU(0x74), RGBU(0x75), RGBU(0x76), RGBU(0x77),
-  RGBU(0x78), RGBU(0x79), RGBU(0x7A), RGBU(0x7B),
-  RGBU(0x7C), RGBU(0x7D), RGBU(0x7E), RGBU(0x7F),
-  RGBU(0x80), RGBU(0x81), RGBU(0x82), RGBU(0x83),
-  RGBU(0x84), RGBU(0x85), RGBU(0x86), RGBU(0x87),
-  RGBU(0x88), RGBU(0x89), RGBU(0x8A), RGBU(0x8B),
-  RGBU(0x8C), RGBU(0x8D), RGBU(0x8E), RGBU(0x8F),
-  RGBU(0x90), RGBU(0x91), RGBU(0x92), RGBU(0x93),
-  RGBU(0x94), RGBU(0x95), RGBU(0x96), RGBU(0x97),
-  RGBU(0x98), RGBU(0x99), RGBU(0x9A), RGBU(0x9B),
-  RGBU(0x9C), RGBU(0x9D), RGBU(0x9E), RGBU(0x9F),
-  RGBU(0xA0), RGBU(0xA1), RGBU(0xA2), RGBU(0xA3),
-  RGBU(0xA4), RGBU(0xA5), RGBU(0xA6), RGBU(0xA7),
-  RGBU(0xA8), RGBU(0xA9), RGBU(0xAA), RGBU(0xAB),
-  RGBU(0xAC), RGBU(0xAD), RGBU(0xAE), RGBU(0xAF),
-  RGBU(0xB0), RGBU(0xB1), RGBU(0xB2), RGBU(0xB3),
-  RGBU(0xB4), RGBU(0xB5), RGBU(0xB6), RGBU(0xB7),
-  RGBU(0xB8), RGBU(0xB9), RGBU(0xBA), RGBU(0xBB),
-  RGBU(0xBC), RGBU(0xBD), RGBU(0xBE), RGBU(0xBF),
-  RGBU(0xC0), RGBU(0xC1), RGBU(0xC2), RGBU(0xC3),
-  RGBU(0xC4), RGBU(0xC5), RGBU(0xC6), RGBU(0xC7),
-  RGBU(0xC8), RGBU(0xC9), RGBU(0xCA), RGBU(0xCB),
-  RGBU(0xCC), RGBU(0xCD), RGBU(0xCE), RGBU(0xCF),
-  RGBU(0xD0), RGBU(0xD1), RGBU(0xD2), RGBU(0xD3),
-  RGBU(0xD4), RGBU(0xD5), RGBU(0xD6), RGBU(0xD7),
-  RGBU(0xD8), RGBU(0xD9), RGBU(0xDA), RGBU(0xDB),
-  RGBU(0xDC), RGBU(0xDD), RGBU(0xDE), RGBU(0xDF),
-  RGBU(0xE0), RGBU(0xE1), RGBU(0xE2), RGBU(0xE3),
-  RGBU(0xE4), RGBU(0xE5), RGBU(0xE6), RGBU(0xE7),
-  RGBU(0xE8), RGBU(0xE9), RGBU(0xEA), RGBU(0xEB),
-  RGBU(0xEC), RGBU(0xED), RGBU(0xEE), RGBU(0xEF),
-  RGBU(0xF0), RGBU(0xF1), RGBU(0xF2), RGBU(0xF3),
-  RGBU(0xF4), RGBU(0xF5), RGBU(0xF6), RGBU(0xF7),
-  RGBU(0xF8), RGBU(0xF9), RGBU(0xFA), RGBU(0xFB),
-  RGBU(0xFC), RGBU(0xFD), RGBU(0xFE), RGBU(0xFF),
-
-  // Chroma V table.
-  RGBV(0x00), RGBV(0x01), RGBV(0x02), RGBV(0x03),
-  RGBV(0x04), RGBV(0x05), RGBV(0x06), RGBV(0x07),
-  RGBV(0x08), RGBV(0x09), RGBV(0x0A), RGBV(0x0B),
-  RGBV(0x0C), RGBV(0x0D), RGBV(0x0E), RGBV(0x0F),
-  RGBV(0x10), RGBV(0x11), RGBV(0x12), RGBV(0x13),
-  RGBV(0x14), RGBV(0x15), RGBV(0x16), RGBV(0x17),
-  RGBV(0x18), RGBV(0x19), RGBV(0x1A), RGBV(0x1B),
-  RGBV(0x1C), RGBV(0x1D), RGBV(0x1E), RGBV(0x1F),
-  RGBV(0x20), RGBV(0x21), RGBV(0x22), RGBV(0x23),
-  RGBV(0x24), RGBV(0x25), RGBV(0x26), RGBV(0x27),
-  RGBV(0x28), RGBV(0x29), RGBV(0x2A), RGBV(0x2B),
-  RGBV(0x2C), RGBV(0x2D), RGBV(0x2E), RGBV(0x2F),
-  RGBV(0x30), RGBV(0x31), RGBV(0x32), RGBV(0x33),
-  RGBV(0x34), RGBV(0x35), RGBV(0x36), RGBV(0x37),
-  RGBV(0x38), RGBV(0x39), RGBV(0x3A), RGBV(0x3B),
-  RGBV(0x3C), RGBV(0x3D), RGBV(0x3E), RGBV(0x3F),
-  RGBV(0x40), RGBV(0x41), RGBV(0x42), RGBV(0x43),
-  RGBV(0x44), RGBV(0x45), RGBV(0x46), RGBV(0x47),
-  RGBV(0x48), RGBV(0x49), RGBV(0x4A), RGBV(0x4B),
-  RGBV(0x4C), RGBV(0x4D), RGBV(0x4E), RGBV(0x4F),
-  RGBV(0x50), RGBV(0x51), RGBV(0x52), RGBV(0x53),
-  RGBV(0x54), RGBV(0x55), RGBV(0x56), RGBV(0x57),
-  RGBV(0x58), RGBV(0x59), RGBV(0x5A), RGBV(0x5B),
-  RGBV(0x5C), RGBV(0x5D), RGBV(0x5E), RGBV(0x5F),
-  RGBV(0x60), RGBV(0x61), RGBV(0x62), RGBV(0x63),
-  RGBV(0x64), RGBV(0x65), RGBV(0x66), RGBV(0x67),
-  RGBV(0x68), RGBV(0x69), RGBV(0x6A), RGBV(0x6B),
-  RGBV(0x6C), RGBV(0x6D), RGBV(0x6E), RGBV(0x6F),
-  RGBV(0x70), RGBV(0x71), RGBV(0x72), RGBV(0x73),
-  RGBV(0x74), RGBV(0x75), RGBV(0x76), RGBV(0x77),
-  RGBV(0x78), RGBV(0x79), RGBV(0x7A), RGBV(0x7B),
-  RGBV(0x7C), RGBV(0x7D), RGBV(0x7E), RGBV(0x7F),
-  RGBV(0x80), RGBV(0x81), RGBV(0x82), RGBV(0x83),
-  RGBV(0x84), RGBV(0x85), RGBV(0x86), RGBV(0x87),
-  RGBV(0x88), RGBV(0x89), RGBV(0x8A), RGBV(0x8B),
-  RGBV(0x8C), RGBV(0x8D), RGBV(0x8E), RGBV(0x8F),
-  RGBV(0x90), RGBV(0x91), RGBV(0x92), RGBV(0x93),
-  RGBV(0x94), RGBV(0x95), RGBV(0x96), RGBV(0x97),
-  RGBV(0x98), RGBV(0x99), RGBV(0x9A), RGBV(0x9B),
-  RGBV(0x9C), RGBV(0x9D), RGBV(0x9E), RGBV(0x9F),
-  RGBV(0xA0), RGBV(0xA1), RGBV(0xA2), RGBV(0xA3),
-  RGBV(0xA4), RGBV(0xA5), RGBV(0xA6), RGBV(0xA7),
-  RGBV(0xA8), RGBV(0xA9), RGBV(0xAA), RGBV(0xAB),
-  RGBV(0xAC), RGBV(0xAD), RGBV(0xAE), RGBV(0xAF),
-  RGBV(0xB0), RGBV(0xB1), RGBV(0xB2), RGBV(0xB3),
-  RGBV(0xB4), RGBV(0xB5), RGBV(0xB6), RGBV(0xB7),
-  RGBV(0xB8), RGBV(0xB9), RGBV(0xBA), RGBV(0xBB),
-  RGBV(0xBC), RGBV(0xBD), RGBV(0xBE), RGBV(0xBF),
-  RGBV(0xC0), RGBV(0xC1), RGBV(0xC2), RGBV(0xC3),
-  RGBV(0xC4), RGBV(0xC5), RGBV(0xC6), RGBV(0xC7),
-  RGBV(0xC8), RGBV(0xC9), RGBV(0xCA), RGBV(0xCB),
-  RGBV(0xCC), RGBV(0xCD), RGBV(0xCE), RGBV(0xCF),
-  RGBV(0xD0), RGBV(0xD1), RGBV(0xD2), RGBV(0xD3),
-  RGBV(0xD4), RGBV(0xD5), RGBV(0xD6), RGBV(0xD7),
-  RGBV(0xD8), RGBV(0xD9), RGBV(0xDA), RGBV(0xDB),
-  RGBV(0xDC), RGBV(0xDD), RGBV(0xDE), RGBV(0xDF),
-  RGBV(0xE0), RGBV(0xE1), RGBV(0xE2), RGBV(0xE3),
-  RGBV(0xE4), RGBV(0xE5), RGBV(0xE6), RGBV(0xE7),
-  RGBV(0xE8), RGBV(0xE9), RGBV(0xEA), RGBV(0xEB),
-  RGBV(0xEC), RGBV(0xED), RGBV(0xEE), RGBV(0xEF),
-  RGBV(0xF0), RGBV(0xF1), RGBV(0xF2), RGBV(0xF3),
-  RGBV(0xF4), RGBV(0xF5), RGBV(0xF6), RGBV(0xF7),
-  RGBV(0xF8), RGBV(0xF9), RGBV(0xFA), RGBV(0xFB),
-  RGBV(0xFC), RGBV(0xFD), RGBV(0xFE), RGBV(0xFF),
-};
-
-#undef RGBY
-#undef RGBU
-#undef RGBV
-#undef MMX_ALIGNED
-
-#if defined(ARCH_CPU_X86_64)
+#if USE_SSE2 && defined(ARCH_CPU_X86_64)
 
 // AMD64 ABI uses register paremters.
 void FastConvertYUVToRGB32Row(const uint8* y_buf,  // rdi
                               const uint8* u_buf,  // rsi
                               const uint8* v_buf,  // rdx
                               uint8* rgb_buf,      // rcx
-                              int width) {         // r8
+                              int source_width) {         // r8
   asm(
   "jmp    convertend\n"
 "convertloop:"
   "movzb  (%1),%%r10\n"
   "add    $0x1,%1\n"
   "movzb  (%2),%%r11\n"
   "add    $0x1,%2\n"
   "movq   2048(%5,%%r10,8),%%xmm0\n"
   "movzb  (%0),%%r10\n"
   "movq   4096(%5,%%r11,8),%%xmm1\n"
@@ skipping 27 matching lines @@
   "paddsw %%xmm0,%%xmm1\n"
   "psraw  $0x6,%%xmm1\n"
   "packuswb %%xmm1,%%xmm1\n"
   "movd   %%xmm1,0x0(%3)\n"
 "convertdone:"
   :
   : "r"(y_buf),  // %0
     "r"(u_buf),  // %1
     "r"(v_buf),  // %2
     "r"(rgb_buf),  // %3
-    "r"(width),  // %4
+    "r"(source_width),  // %4
     "r" (kCoefficientsRgbY)  // %5
   : "memory", "r10", "r11", "xmm0", "xmm1", "xmm2", "xmm3"
 );
 }
 
 void ScaleYUVToRGB32Row(const uint8* y_buf,  // rdi
                         const uint8* u_buf,  // rsi
                         const uint8* v_buf,  // rdx
                         uint8* rgb_buf,      // rcx
-                        int width,           // r8
-                        int scaled_dx) {     // r9
+                        int source_width,           // r8
+                        int source_dx) {     // r9
   asm(
   "xor    %%r11,%%r11\n"
   "sub    $0x2,%4\n"
   "js     scalenext\n"
 
 "scaleloop:"
   "mov    %%r11,%%r10\n"
   "sar    $0x11,%%r10\n"
   "movzb  (%1,%%r10,1),%%rax\n"
   "movq   2048(%5,%%rax,8),%%xmm0\n"
@@ skipping 36 matching lines @@
   "psraw  $0x6,%%xmm1\n"
   "packuswb %%xmm1,%%xmm1\n"
   "movd   %%xmm1,0x0(%3)\n"
 
 "scaledone:"
   :
   : "r"(y_buf),  // %0
     "r"(u_buf),  // %1
     "r"(v_buf),  // %2
     "r"(rgb_buf),  // %3
-    "r"(width),  // %4
+    "r"(source_width),  // %4
     "r" (kCoefficientsRgbY),  // %5
-    "r"(static_cast<long>(scaled_dx))  // %6
+    "r"(static_cast<long>(source_dx))  // %6
   : "memory", "r10", "r11", "rax", "xmm0", "xmm1", "xmm2"
 );
 }
 
 void LinearScaleYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width,
-                              int scaled_dx) {
+                              int source_width,
+                              int source_dx) {
   asm(
   "xor    %%r11,%%r11\n"
   "sub    $0x2,%4\n"
   "js     .lscalenext\n"
 
 ".lscaleloop:"
   "mov    %%r11,%%r10\n"
   "sar    $0x11,%%r10\n"
 
   "movzb  (%1, %%r10, 1), %%r13 \n"
@@ skipping 80 matching lines @@
   "psraw  $0x6,%%xmm1\n"
   "packuswb %%xmm1,%%xmm1\n"
   "movd   %%xmm1,0x0(%3)\n"
 
 ".lscaledone:"
   :
   : "r"(y_buf),  // %0
     "r"(u_buf),  // %1
     "r"(v_buf),  // %2
     "r"(rgb_buf),  // %3
-    "r"(width),  // %4
+    "r"(source_width),  // %4
     "r" (kCoefficientsRgbY),  // %5
-    "r"(static_cast<long>(scaled_dx))  // %6
+    "r"(static_cast<long>(source_dx))  // %6
   : "memory", "r10", "r11", "r13", "r14", "rax", "xmm0", "xmm1", "xmm2"
 );
 }
 
-#else // !AMD64
+#elif USE_MMX && !defined(ARCH_CPU_X86_64) && !defined(__PIC__)
 
 // PIC version is slower because less registers are available, so
 // non-PIC is used on platforms where it is possible.
 
-#if !defined(__PIC__)
-
 void FastConvertYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width);
+                              int source_width);
 
   asm(
   ".global FastConvertYUVToRGB32Row\n"
 "FastConvertYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x28(%esp),%edi\n"
   "mov    0x2c(%esp),%esi\n"
   "mov    0x30(%esp),%ebp\n"
   "mov    0x34(%esp),%ecx\n"
@@ skipping 38 matching lines @@
 "convertdone:"
   "popa\n"
   "ret\n"
 );
 
 
 void ScaleYUVToRGB32Row(const uint8* y_buf,
                         const uint8* u_buf,
                         const uint8* v_buf,
                         uint8* rgb_buf,
-                        int width,
-                        int scaled_dx);
+                        int source_width,
+                        int source_dx);
 
   asm(
   ".global ScaleYUVToRGB32Row\n"
 "ScaleYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x28(%esp),%edi\n"
   "mov    0x2c(%esp),%esi\n"
   "mov    0x30(%esp),%ebp\n"
   "mov    0x34(%esp),%ecx\n"
@@ skipping 52 matching lines @@
 
 "scaledone:"
   "popa\n"
   "ret\n"
 );
 
 void LinearScaleYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width,
-                              int scaled_dx);
+                              int source_width,
+                              int source_dx);
 
   asm(
   ".global LinearScaleYUVToRGB32Row\n"
 "LinearScaleYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x28(%esp),%edi\n"
   "mov    0x30(%esp),%ebp\n"
   "xor    %ebx,%ebx\n"
 
-  // width = width * scaled_dx + ebx
+  // source_width = source_width * source_dx + ebx
   "mov    0x34(%esp), %ecx\n"
   "imull  0x38(%esp), %ecx\n"
   "addl   %ebx, %ecx\n"
   "mov    %ecx, 0x34(%esp)\n"
 
   "jmp    .lscaleend\n"
 
 ".lscaleloop:"
   "mov    %ebx,%eax\n"
   "sar    $0x11,%eax\n"
@@ skipping 71 matching lines @@
 
 ".lscalelastpixel:"
   "paddsw %mm0, %mm1\n"
   "psraw $6, %mm1\n"
   "packuswb %mm1, %mm1\n"
   "movd %mm1, (%ebp)\n"
   "popa\n"
   "ret\n"
 );
 
-#else // __PIC__
+#elif USE_MMX && !defined(ARCH_CPU_X86_64) && defined(__PIC__)
 
 extern void PICConvertYUVToRGB32Row(const uint8* y_buf,
                                     const uint8* u_buf,
                                     const uint8* v_buf,
                                     uint8* rgb_buf,
-                                    int width,
+                                    int source_width,
                                     int16 *kCoefficientsRgbY);
   __asm__(
 "_PICConvertYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x28(%esp),%edi\n"
   "mov    0x2c(%esp),%esi\n"
   "mov    0x30(%esp),%ebp\n"
   "mov    0x38(%esp),%ecx\n"
 
@@ skipping 37 matching lines @@
   "movd   %mm1,0x0(%ebp)\n"
 ".Lconvertdone:\n"
   "popa\n"
   "ret\n"
 );
 
 void FastConvertYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width) {
-  PICConvertYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, width,
+                              int source_width) {
+  PICConvertYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, source_width,
                           &kCoefficientsRgbY[0][0]);
 }
 
 extern void PICScaleYUVToRGB32Row(const uint8* y_buf,
                                const uint8* u_buf,
                                const uint8* v_buf,
                                uint8* rgb_buf,
-                               int width,
-                               int scaled_dx,
+                               int source_width,
+                               int source_dx,
                                int16 *kCoefficientsRgbY);
 
   __asm__(
 "_PICScaleYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x28(%esp),%edi\n"
   "mov    0x2c(%esp),%esi\n"
   "mov    0x30(%esp),%ebp\n"
   "mov    0x3c(%esp),%ecx\n"
@@ skipping 53 matching lines @@
 "Lscaledone:"
   "popa\n"
   "ret\n"
 );
 
 
 void ScaleYUVToRGB32Row(const uint8* y_buf,
                         const uint8* u_buf,
                         const uint8* v_buf,
                         uint8* rgb_buf,
-                        int width,
-                        int scaled_dx) {
-  PICScaleYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, width, scaled_dx,
+                        int source_width,
+                        int source_dx) {
+  PICScaleYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, source_width, source_dx,
                         &kCoefficientsRgbY[0][0]);
 }
 
 void PICLinearScaleYUVToRGB32Row(const uint8* y_buf,
                                  const uint8* u_buf,
                                  const uint8* v_buf,
                                  uint8* rgb_buf,
-                                 int width,
-                                 int scaled_dx,
+                                 int source_width,
+                                 int source_dx,
                                  int16 *kCoefficientsRgbY);
 
   asm(
 "_PICLinearScaleYUVToRGB32Row:\n"
   "pusha\n"
   "mov    0x24(%esp),%edx\n"
   "mov    0x30(%esp),%ebp\n"
   "mov    0x34(%esp),%ecx\n"
   "mov    0x3c(%esp),%edi\n"
   "xor    %ebx,%ebx\n"
 
-  // width = width * scaled_dx + ebx
+  // source_width = source_width * source_dx + ebx
   "mov    0x34(%esp), %ecx\n"
   "imull  0x38(%esp), %ecx\n"
   "addl   %ebx, %ecx\n"
   "mov    %ecx, 0x34(%esp)\n"
 
   "jmp    .lscaleend\n"
 
 ".lscaleloop:"
   "mov    0x28(%esp),%esi\n"
   "mov    %ebx,%eax\n"
@@ skipping 76 matching lines @@
   "packuswb %mm1, %mm1\n"
   "movd %mm1, (%ebp)\n"
   "popa\n"
   "ret\n"
 );
 
 void LinearScaleYUVToRGB32Row(const uint8* y_buf,
                         const uint8* u_buf,
                         const uint8* v_buf,
                         uint8* rgb_buf,
-                        int width,
-                        int scaled_dx) {
-  PICLinearScaleYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, width, scaled_dx,
+                        int source_width,
+                        int source_dx) {
+  PICLinearScaleYUVToRGB32Row(y_buf, u_buf, v_buf, rgb_buf, source_width, source_dx,
                               &kCoefficientsRgbY[0][0]);
 }
 
-#endif // !__PIC__
+#else  // Use C code instead of MMX/SSE2.
 
-#endif // !AMD64
-
-#else  // USE_MMX
-
-// Reference version of YUV converter.
-static const int kClipTableSize = 256;
-static const int kClipOverflow = 288;  // Cb max is 535.
-
-static uint8 kRgbClipTable[kClipOverflow +
-                           kClipTableSize +
-                           kClipOverflow] = {
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // 288 underflow values
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,  // clipped to 0.
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,  // Unclipped values.
-  0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
-  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
-  0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
-  0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
-  0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F,
-  0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
-  0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
-  0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
-  0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x4E, 0x4F,
-  0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
-  0x58, 0x59, 0x5A, 0x5B, 0x5C, 0x5D, 0x5E, 0x5F,
-  0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
-  0x68, 0x69, 0x6A, 0x6B, 0x6C, 0x6D, 0x6E, 0x6F,
-  0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
-  0x78, 0x79, 0x7A, 0x7B, 0x7C, 0x7D, 0x7E, 0x7F,
-  0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
-  0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F,
-  0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
-  0x98, 0x99, 0x9A, 0x9B, 0x9C, 0x9D, 0x9E, 0x9F,
-  0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7,
-  0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF,
-  0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7,
-  0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF,
-  0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7,
-  0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF,
-  0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7,
-  0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF,
-  0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7,
-  0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF,
-  0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
-  0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,  // 288 overflow values
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,  // clipped to 255.
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-};
-
-// Clip an rgb channel value to 0..255 range.
-// Source is signed fixed point 8.8.
-// Table allows for values to underflow or overflow by 128.
-// Therefore source range is -128 to 384.
-// Output clips to unsigned 0 to 255.
-static inline uint32 clip(int32 value) {
-  DCHECK(((value >> 8) + kClipOverflow) >= 0);
-  DCHECK(((value >> 8) + kClipOverflow) <
-         (kClipOverflow + kClipTableSize + kClipOverflow));
-  return static_cast<uint32>(kRgbClipTable[((value) >> 8) + kClipOverflow]);
-}
+// C reference code that mimic the YUV assembly.
+#define packuswb(x) ((x) < 0 ? 0 : ((x) > 255 ? 255 : (x)))
+#define paddsw(x, y) (((x) + (y)) < -32768 ? -32768 : \\
+    (((x) + (y)) > 32767 ? 32767 : ((x) + (y))))
 
 static inline void YuvPixel(uint8 y,
                             uint8 u,
                             uint8 v,
                             uint8* rgb_buf) {
-  int32 d = static_cast<int32>(u) - 128;
-  int32 e = static_cast<int32>(v) - 128;
 
-  int32 cb =   (516 * d + 128);
-  int32 cg = (- 100 * d - 208 * e + 128);
-  int32 cr =             (409 * e + 128);
+  int b = kCoefficientsRgbY[256+u][0];
+  int g = kCoefficientsRgbY[256+u][1];
+  int r = kCoefficientsRgbY[256+u][2];
+  int a = kCoefficientsRgbY[256+u][3];
 
-  int32 C298a = ((static_cast<int32>(y) - 16) * 298 + 128);
-  *reinterpret_cast<uint32*>(rgb_buf) = (clip(C298a + cb)) |
-                                        (clip(C298a + cg) << 8) |
-                                        (clip(C298a + cr) << 16) |
-                                        (0xff000000);
+  b = paddsw(b, kCoefficientsRgbY[512+v][0]);
+  g = paddsw(g, kCoefficientsRgbY[512+v][1]);
+  r = paddsw(r, kCoefficientsRgbY[512+v][2]);
+  a = paddsw(a, kCoefficientsRgbY[512+v][3]);
+
+  b = paddsw(b, kCoefficientsRgbY[y][0]);
+  g = paddsw(g, kCoefficientsRgbY[y][1]);
+  r = paddsw(r, kCoefficientsRgbY[y][2]);
+  a = paddsw(a, kCoefficientsRgbY[y][3]);
+
+  b >>= 6;
+  g >>= 6;
+  r >>= 6;
+  a >>= 6;
+
+  *reinterpret_cast<uint32*>(rgb_buf) = (packuswb(b)) |
+                                        (packuswb(g) << 8) |
+                                        (packuswb(r) << 16) |
+                                        (packuswb(a) << 24);
 }
 
+#if TEST_MMX_YUV
+static inline void YuvPixel(uint8 y,
+                            uint8 u,
+                            uint8 v,
+                            uint8* rgb_buf) {
+
+  __asm {
+    movzx     eax, u
+    movq      mm0, [kCoefficientsRgbY+2048 + 8 * eax]
+    movzx     eax, v
+    paddsw    mm0, [kCoefficientsRgbY+4096 + 8 * eax]
+    movzx     eax, y
+    movq      mm1, [kCoefficientsRgbY + 8 * eax]
+    paddsw    mm1, mm0
+    psraw     mm1, 6
+    packuswb  mm1, mm1
+    mov       eax, rgb_buf
+    movd      [eax], mm1
+    emms
+  }
+}
+#endif
+
 void FastConvertYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width) {
-  for (int x = 0; x < width; x += 2) {
+                              int source_width) {
+  for (int x = 0; x < source_width; x += 2) {
     uint8 u = u_buf[x >> 1];
     uint8 v = v_buf[x >> 1];
     uint8 y0 = y_buf[x];
     YuvPixel(y0, u, v, rgb_buf);
-    if ((x + 1) < width) {
+    if ((x + 1) < source_width) {
       uint8 y1 = y_buf[x + 1];
       YuvPixel(y1, u, v, rgb_buf + 4);
     }
     rgb_buf += 8;  // Advance 2 pixels.
   }
 }
 
 // 16.16 fixed point is used.  A shift by 16 isolates the integer.
 // A shift by 17 is used to further subsample the chrominence channels.
 // & 0xffff isolates the fixed point fraction.  >> 2 to get the upper 2 bits,
 // for 1/65536 pixel accurate interpolation.
 void ScaleYUVToRGB32Row(const uint8* y_buf,
                         const uint8* u_buf,
                         const uint8* v_buf,
                         uint8* rgb_buf,
-                        int width,
-                        int scaled_dx) {
-  int scaled_x = 0;
-  for (int x = 0; x < width; ++x) {
-    uint8 u = u_buf[scaled_x >> 17];
-    uint8 v = v_buf[scaled_x >> 17];
-    uint8 y0 = y_buf[scaled_x >> 16];
-    YuvPixel(y0, u, v, rgb_buf);
-    rgb_buf += 4;
-    scaled_x += scaled_dx;
+                        int source_width,
+                        int dx) {
+  int x = 0;
+  for (int i = 0; i < source_width; i += 2) {
+    int y = y_buf[x >> 16];
+    int u = u_buf[(x >> 17)];
+    int v = v_buf[(x >> 17)];
+    YuvPixel(y, u, v, rgb_buf);
+    x += dx;
+    if ((i + 1) < source_width) {
+      y = y_buf[x >> 16];
+      YuvPixel(y, u, v, rgb_buf+4);
+      x += dx;
+    }
+    rgb_buf += 8;
   }
 }
 
 void LinearScaleYUVToRGB32Row(const uint8* y_buf,
                               const uint8* u_buf,
                               const uint8* v_buf,
                               uint8* rgb_buf,
-                              int width,
+                              int source_width,
                               int dx) {
-  for (int x = 0; x < width * dx; x += dx) {
+  int x = 0;
+  for (int i = 0; i < source_width; i += 2) {
     int y0 = y_buf[x >> 16];
     int y1 = y_buf[(x >> 16) + 1];
     int u0 = u_buf[(x >> 17)];
     int u1 = u_buf[(x >> 17) + 1];
     int v0 = v_buf[(x >> 17)];
     int v1 = v_buf[(x >> 17) + 1];
-    int y = ((x & 65535) * y1 + ((x & 65535) ^ 65535) * y0) >> 16;
-    int u = ((x & 65535) * u1 + ((x & 65535) ^ 65535) * u0) >> 16;
-    int v = ((x & 65535) * v1 + ((x & 65535) ^ 65535) * v0) >> 16;
+    int y_frac = (x & 65535);
+    int uv_frac = ((x >> 1) & 65535);
+    int y = (y_frac * y1 + (y_frac ^ 65535) * y0) >> 16;
+    int u = (uv_frac * u1 + (uv_frac ^ 65535) * u0) >> 16;
+    int v = (uv_frac * v1 + (uv_frac ^ 65535) * v0) >> 16;
     YuvPixel(y, u, v, rgb_buf);
-    rgb_buf += 4;
+    x += dx;
+    if ((i + 1) < source_width) {
+      y0 = y_buf[x >> 16];
+      y1 = y_buf[(x >> 16) + 1];
+      y_frac = (x & 65535);
+      y = (y_frac * y1 + (y_frac ^ 65535) * y0) >> 16;
+      YuvPixel(y, u, v, rgb_buf+4);
+      x += dx;
+    }
+    rgb_buf += 8;
   }
 }
 
 #endif  // USE_MMX
 }  // extern "C"
+