// Copyright (c) 2009 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.
// This webpage shows layout of YV12 and other YUV formats
// http://www.fourcc.org/yuv.php
// The actual conversion is best described here
// http://en.wikipedia.org/wiki/YUV
// excerpt from wiki:
// These formulae are based on the NTSC standard;
// Y' = 0.299 x R + 0.587 x G + 0.114 x B
// U = -0.147 x R - 0.289 x G + 0.436 x B
// V = 0.615 x R - 0.515 x G - 0.100 x B
// On older, non-SIMD architectures, floating point arithmetic is much
// slower than using fixed-point arithmetic, so an alternative formulation
// is:
// c = Y' - 16
// d = U - 128
// e = V - 128
// Using the previous coefficients and noting that clip() denotes clipping a
// value to the range of 0 to 255, the following formulae provide the
// conversion from Y'UV to RGB (NTSC version):
// R = clip((298 x c + 409 x e + 128) >> 8)
// G = clip((298 x c - 100 x d - 208 x e + 128) >> 8)
// B = clip((298 x c + 516 x d + 128) >> 8)
//
// An article on optimizing YUV conversion using tables instead of multiplies
// http://lestourtereaux.free.fr/papers/data/yuvrgb.pdf
//
// YV12 is a full plane of Y and a half height, half width chroma planes
// YV16 is a full plane of Y and a full height, half width chroma planes
//
// Implimentation notes
// This version uses MMX for Visual C and GCC, which should cover all
// current platforms. C++ is included for reference and future platforms.
//
// ARGB pixel format is output, which on little endian is stored as BGRA.
// The alpha is filled in, allowing the application to use RGBA or RGB32.
//
// The Visual C assembler is considered the source.
// The GCC asm was created by compiling with Visual C and disassembling
// with GNU objdump.
// cl /c /Ox yuv_convert.cc
// objdump -d yuv_convert.o
// The code almost copy/pasted in, except the table lookups, which produced
// movq 0x800(,%eax,8),%mm0
// and needed to be changed to cdecl style table names
// "movq _coefficients_RGB_U(,%eax,8),%mm0\n"
// extern "C" was used to avoid name mangling.
//
// Once compiled with both MinGW GCC and Visual C on PC, performance should
// be identical. A small difference will occur in the C++ calling code,
// depending on the frame size.
// To confirm the same code is being generated
// g++ -O3 -c yuv_convert.cc
// dumpbin -disasm yuv_convert.o >gcc.txt
// cl /Ox /c yuv_convert.cc
// dumpbin -disasm yuv_convert.obj >vc.txt
// and compare the files.
//
// The GCC function label is inside the assembler to avoid a stack frame
// push ebp, that may vary depending on compile options.
#include "media/base/yuv_convert.h"
#ifdef _OPENMP
#include <omp.h>
#endif
#ifdef _DEBUG
#include "base/logging.h"
#else
#define DCHECK(a)
#endif
// Header for low level row functions.
#include "media/base/yuv_row.h"
namespace media {
// Convert a frame of YUV to 32 bit ARGB.
void ConvertYUVToRGB32(const uint8* y_buf,
const uint8* u_buf,
const uint8* v_buf,
uint8* rgb_buf,
int width,
int height,
int y_pitch,
int uv_pitch,
int rgb_pitch,
YUVType yuv_type) {
unsigned int y_shift = yuv_type;
#ifdef _OPENMP
#pragma omp parallel for
#endif
for (int y = 0; y < height; ++y) {
uint8* rgb_row = rgb_buf + y * rgb_pitch;
const uint8* y_ptr = y_buf + y * y_pitch;
const uint8* u_ptr = u_buf + (y >> y_shift) * uv_pitch;
const uint8* v_ptr = v_buf + (y >> y_shift) * uv_pitch;
FastConvertYUVToRGB32Row(y_ptr,
u_ptr,
v_ptr,
rgb_row,
width);
}
EMMS();
}
// Scale a frame of YUV to 32 bit ARGB.
void ScaleYUVToRGB32(const uint8* y_buf,
const uint8* u_buf,
const uint8* v_buf,
uint8* rgb_buf,
int width,
int height,
int scaled_width,
int scaled_height,
int y_pitch,
int uv_pitch,
int rgb_pitch,
YUVType yuv_type,
Rotate view_rotate) {
unsigned int y_shift = yuv_type;
// Diagram showing origin and direction of source sampling.
// ->0 4<-
// 7 3
//
// 6 5
// ->1 2<-
// Rotations that start at right side of image.
if ((view_rotate == ROTATE_180) ||
(view_rotate == ROTATE_270) ||
(view_rotate == MIRROR_ROTATE_0) ||
(view_rotate == MIRROR_ROTATE_90)) {
y_buf += width - 1;
u_buf += width / 2 - 1;
v_buf += width / 2 - 1;
width = -width;
}
// Rotations that start at bottom of image.
if ((view_rotate == ROTATE_90) ||
(view_rotate == ROTATE_180) ||
(view_rotate == MIRROR_ROTATE_90) ||
(view_rotate == MIRROR_ROTATE_180)) {
y_buf += (height - 1) * y_pitch;
u_buf += ((height >> y_shift) - 1) * uv_pitch;
v_buf += ((height >> y_shift) - 1) * uv_pitch;
height = -height;
}
// Handle zero sized destination.
if (scaled_width == 0 || scaled_height == 0)
return;
int scaled_dx = width * 16 / scaled_width;
int scaled_dy = height * 16 / scaled_height;
int scaled_dx_uv = scaled_dx;
if ((view_rotate == ROTATE_90) ||
(view_rotate == ROTATE_270)) {
int tmp = scaled_height;
scaled_height = scaled_width;
scaled_width = tmp;
tmp = height;
height = width;
width = tmp;
int original_dx = scaled_dx;
int original_dy = scaled_dy;
scaled_dx = ((original_dy >> 4) * y_pitch) << 4;
scaled_dx_uv = ((original_dy >> 4) * uv_pitch) << 4;
scaled_dy = original_dx;
if (view_rotate == ROTATE_90) {
y_pitch = -1;
uv_pitch = -1;
height = -height;
} else {
y_pitch = 1;
uv_pitch = 1;
}
}
#ifdef _OPENMP
#pragma omp parallel for
#endif
for (int y = 0; y < scaled_height; ++y) {
uint8* dest_pixel = rgb_buf + y * rgb_pitch;
int scaled_y = (y * height / scaled_height);
const uint8* y_ptr = y_buf + scaled_y * y_pitch;
const uint8* u_ptr = u_buf + (scaled_y >> y_shift) * uv_pitch;
const uint8* v_ptr = v_buf + (scaled_y >> y_shift) * uv_pitch;
#if USE_MMX
if (scaled_width == (width * 2)) {
DoubleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width);
} else if ((scaled_dx & 15) == 0) { // Scaling by integer scale factor.
if (scaled_dx_uv == scaled_dx) { // Not rotated.
if (scaled_dx == 16) { // Not scaled
FastConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width);
} else { // Simple scale down. ie half
ConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width, scaled_dx >> 4);
}
} else {
RotateConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width,
scaled_dx >> 4, scaled_dx_uv >> 4);
}
#else
if (scaled_dx == 16) { // Not scaled
FastConvertYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width);
#endif
} else {
ScaleYUVToRGB32Row(y_ptr, u_ptr, v_ptr,
dest_pixel, scaled_width, scaled_dx);
}
}
EMMS();
}
} // namespace media