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add LUT-free reference code for YUV->RGB conversion.

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Reported to eventually be 4% on ARM
(see https://code.google.com/p/webp/issues/detail?id=134 for details)
We might activate it selectively later...

Output values is not bitwise the same as the LUT-based
version, but difference is only +/-1 at max.

Change-Id: I1cc790ff4459885ed2ae2e72f31c5f3740095f07
This commit is contained in:
skal 2013-03-14 20:28:29 +01:00
parent 14ef5005a2
commit 126974b45b
2 changed files with 112 additions and 15 deletions
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8
src/dsp/yuv.c
View File

@ -15,7 +15,7 @@
extern "C" {
#endif
enum { YUV_HALF = 1 << (YUV_FIX - 1) };
#ifdef WEBP_YUV_USE_TABLE
int16_t VP8kVToR[256], VP8kUToB[256];
int32_t VP8kVToG[256], VP8kUToG[256];
@ -62,6 +62,12 @@ void VP8YUVInit(void) {
done = 1;
}
#else
void VP8YUVInit(void) {}
#endif // WEBP_YUV_USE_TABLE
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif

119
src/dsp/yuv.h
View File

@ -19,8 +19,9 @@
// G = 1.164 * (Y-16) - 0.813 * (V-128) - 0.391 * (U-128)
// B = 1.164 * (Y-16) + 2.018 * (U-128)
// where Y is in the [16,235] range, and U/V in the [16,240] range.
// But the common term 1.164 * (Y-16) can be handled as an offset in the
// VP8kClip[] table. So the formulae should be read as:
// In the table-lookup version (WEBP_YUV_USE_TABLE), the common factor
// "1.164 * (Y-16)" can be handled as an offset in the VP8kClip[] table.
// So in this case the formulae should be read as:
// R = 1.164 * [Y + 1.371 * (V-128) ] - 18.624
// G = 1.164 * [Y - 0.698 * (V-128) - 0.336 * (U-128)] - 18.624
// B = 1.164 * [Y + 1.733 * (U-128)] - 18.624
@ -33,6 +34,9 @@
#include "../dec/decode_vp8.h"
// Define the following to use the LUT-based code:
#define WEBP_YUV_USE_TABLE
#if defined(WEBP_EXPERIMENTAL_FEATURES)
// Do NOT activate this feature for real compression. This is only experimental!
// This flag is for comparison purpose against JPEG's "YUVj" natural colorspace.
@ -51,9 +55,14 @@ extern "C" {
#endif
enum { YUV_FIX = 16, // fixed-point precision
YUV_HALF = 1 << (YUV_FIX - 1),
YUV_MASK = (256 << YUV_FIX) - 1,
YUV_RANGE_MIN = -227, // min value of r/g/b output
YUV_RANGE_MAX = 256 + 226 // max value of r/g/b output
};
#ifdef WEBP_YUV_USE_TABLE
extern int16_t VP8kVToR[256], VP8kUToB[256];
extern int32_t VP8kVToG[256], VP8kUToG[256];
extern uint8_t VP8kClip[YUV_RANGE_MAX - YUV_RANGE_MIN];
@ -69,6 +78,16 @@ static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
rgb[2] = VP8kClip[y + b_off - YUV_RANGE_MIN];
}
static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const bgr) {
const int r_off = VP8kVToR[v];
const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
const int b_off = VP8kUToB[u];
bgr[0] = VP8kClip[y + b_off - YUV_RANGE_MIN];
bgr[1] = VP8kClip[y + g_off - YUV_RANGE_MIN];
bgr[2] = VP8kClip[y + r_off - YUV_RANGE_MIN];
}
static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const rgb) {
const int r_off = VP8kVToR[v];
@ -87,12 +106,6 @@ static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
#endif
}
static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const argb) {
argb[0] = 0xff;
VP8YuvToRgb(y, u, v, argb + 1);
}
static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const argb) {
const int r_off = VP8kVToR[v];
@ -110,14 +123,92 @@ static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
#endif
}
#else // Table-free version (slower on x86)
// These constants are 16b fixed-point version of ITU-R BT.601 constants
#define kYScale 76309 // 1.164 = 255 / 219
#define kVToR 104597 // 1.596 = 255 / 112 * 0.701
#define kUToG 25674 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587
#define kVToG 53278 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587
#define kUToB 132201 // 2.018 = 255 / 112 * 0.886
#define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF)
#define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF)
#define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF)
static WEBP_INLINE uint8_t VP8Clip8(int v) {
return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> YUV_FIX)
: (v < 0) ? 0u : 255u;
}
static WEBP_INLINE uint8_t VP8ClipN(int v, int N) { // clip to N bits
return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> (YUV_FIX + (8 - N)))
: (v < 0) ? 0u : (255u >> (8 - N));
}
static WEBP_INLINE int VP8YUVToR(int y, int v) {
return kYScale * y + kVToR * v + kRCst;
}
static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
return kYScale * y - kUToG * u - kVToG * v + kGCst;
}
static WEBP_INLINE int VP8YUVToB(int y, int u) {
return kYScale * y + kUToB * u + kBCst;
}
static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const rgb) {
rgb[0] = VP8Clip8(VP8YUVToR(y, v));
rgb[1] = VP8Clip8(VP8YUVToG(y, u, v));
rgb[2] = VP8Clip8(VP8YUVToB(y, u));
}
static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const bgr) {
const int r_off = VP8kVToR[v];
const int g_off = (VP8kVToG[v] + VP8kUToG[u]) >> YUV_FIX;
const int b_off = VP8kUToB[u];
bgr[0] = VP8kClip[y + b_off - YUV_RANGE_MIN];
bgr[1] = VP8kClip[y + g_off - YUV_RANGE_MIN];
bgr[2] = VP8kClip[y + r_off - YUV_RANGE_MIN];
bgr[0] = VP8Clip8(VP8YUVToB(y, u));
bgr[1] = VP8Clip8(VP8YUVToG(y, u, v));
bgr[2] = VP8Clip8(VP8YUVToR(y, v));
}
static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const rgb) {
const int r = VP8Clip8(VP8YUVToR(y, u));
const int g = VP8ClipN(VP8YUVToG(y, u, v), 6);
const int b = VP8ClipN(VP8YUVToB(y, v), 5);
const uint8_t rg = (r & 0xf8) | (g >> 3);
const uint8_t gb = (g << 5) | b;
#ifdef WEBP_SWAP_16BIT_CSP
rgb[0] = gb;
rgb[1] = rg;
#else
rgb[0] = rg;
rgb[1] = gb;
#endif
}
static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const argb) {
const int r = VP8Clip8(VP8YUVToR(y, u));
const int g = VP8ClipN(VP8YUVToG(y, u, v), 4);
const int b = VP8Clip8(VP8YUVToB(y, v));
const uint8_t rg = (r & 0xf0) | g;
const uint8_t ba = b | 0x0f; // overwrite the lower 4 bits
#ifdef WEBP_SWAP_16BIT_CSP
argb[0] = ba;
argb[1] = rg;
#else
argb[0] = rg;
argb[1] = ba;
#endif
}
#endif // WEBP_YUV_USE_TABLE
static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
uint8_t* const argb) {
argb[0] = 0xff;
VP8YuvToRgb(y, u, v, argb + 1);
}
static WEBP_INLINE void VP8YuvToBgra(uint8_t y, uint8_t u, uint8_t v,