mirror of
https://github.com/webmproject/libwebp.git
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5-7% faster SSE2 versions of YUV->RGB conversion functions
The C-version gets ~7-8% slower in order to match the SSE2 output exactly. The old (now off-by-1) code is kept under the WEBP_YUV_USE_TABLE flag for reference. (note that calc rounding precision is slightly better ~= +0.02dB) on ARM-neon, we somehow recover the ~4% speed that was lost by mimicking the initial C-version (see https://gerrit.chromium.org/gerrit/#/c/41610) Change-Id: Ia4363c5ed9b4c9edff5d932b002e57bb7814bf6f
This commit is contained in:
skal
210
src/dsp/yuv.h
210
src/dsp/yuv.h
@ -14,7 +14,7 @@
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// Y = 0.2569 * R + 0.5044 * G + 0.0979 * B + 16
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// U = -0.1483 * R - 0.2911 * G + 0.4394 * B + 128
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// V = 0.4394 * R - 0.3679 * G - 0.0715 * B + 128
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// We use 16bit fixed point operations for RGB->YUV conversion.
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// We use 16bit fixed point operations for RGB->YUV conversion (YUV_FIX).
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//
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// For the Y'CbCr to RGB conversion, the BT.601 specification reads:
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// R = 1.164 * (Y-16) + 1.596 * (V-128)
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@ -23,21 +23,24 @@
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// where Y is in the [16,235] range, and U/V in the [16,240] range.
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// In the table-lookup version (WEBP_YUV_USE_TABLE), the common factor
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// "1.164 * (Y-16)" can be handled as an offset in the VP8kClip[] table.
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// So in this case the formulae should be read as:
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// So in this case the formulae should read:
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// R = 1.164 * [Y + 1.371 * (V-128) ] - 18.624
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// G = 1.164 * [Y - 0.698 * (V-128) - 0.336 * (U-128)] - 18.624
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// B = 1.164 * [Y + 1.733 * (U-128)] - 18.624
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// once factorized. Here too, 16bit fixed precision is used.
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// once factorized.
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// For YUV->RGB conversion, only 14bit fixed precision is used (YUV_FIX2).
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// That's the maximum possible for a convenient ARM implementation.
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#ifndef WEBP_DSP_YUV_H_
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#define WEBP_DSP_YUV_H_
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#include "./dsp.h"
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#include "../dec/decode_vp8.h"
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// Define the following to use the LUT-based code:
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#define WEBP_YUV_USE_TABLE
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// #define WEBP_YUV_USE_TABLE
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#if defined(WEBP_EXPERIMENTAL_FEATURES)
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// Do NOT activate this feature for real compression. This is only experimental!
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@ -56,14 +59,100 @@
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extern "C" {
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#endif
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enum { YUV_FIX = 16, // fixed-point precision
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enum {
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YUV_FIX = 16, // fixed-point precision for RGB->YUV
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YUV_HALF = 1 << (YUV_FIX - 1),
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YUV_MASK = (256 << YUV_FIX) - 1,
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YUV_RANGE_MIN = -227, // min value of r/g/b output
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YUV_RANGE_MAX = 256 + 226 // max value of r/g/b output
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YUV_RANGE_MAX = 256 + 226, // max value of r/g/b output
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YUV_FIX2 = 14, // fixed-point precision for YUV->RGB
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YUV_HALF2 = 1 << (YUV_FIX2 - 1),
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YUV_MASK2 = (256 << YUV_FIX2) - 1
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};
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#ifdef WEBP_YUV_USE_TABLE
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// These constants are 14b fixed-point version of ITU-R BT.601 constants.
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#define kYScale 19077 // 1.164 = 255 / 219
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#define kVToR 26149 // 1.596 = 255 / 112 * 0.701
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#define kUToG 6419 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587
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#define kVToG 13320 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587
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#define kUToB 33050 // 2.018 = 255 / 112 * 0.886
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#define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF2)
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#define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF2)
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#define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF2)
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//------------------------------------------------------------------------------
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#ifndef WEBP_YUV_USE_TABLE
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// slower on x86 by ~7-8%, but bit-exact with the SSE2 version
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static WEBP_INLINE uint8_t VP8Clip8(int v) {
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return ((v & ~YUV_MASK2) == 0) ? (v >> YUV_FIX2) : ((~v) >> 31);
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}
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static WEBP_INLINE uint8_t VP8YUVToR(int y, int v) {
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return VP8Clip8(kYScale * y + kVToR * v + kRCst);
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}
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static WEBP_INLINE uint8_t VP8YUVToG(int y, int u, int v) {
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return VP8Clip8(kYScale * y - kUToG * u - kVToG * v + kGCst);
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}
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static WEBP_INLINE uint8_t VP8YUVToB(int y, int u) {
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return VP8Clip8(kYScale * y + kUToB * u + kBCst);
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}
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static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const rgb) {
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rgb[0] = VP8YUVToR(y, v);
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rgb[1] = VP8YUVToG(y, u, v);
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rgb[2] = VP8YUVToB(y, u);
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}
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static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const bgr) {
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bgr[0] = VP8YUVToB(y, u);
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bgr[1] = VP8YUVToG(y, u, v);
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bgr[2] = VP8YUVToR(y, v);
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}
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static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const rgb) {
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const int r = VP8YUVToR(y, v); // 5 usable bits
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const int g = VP8YUVToG(y, u, v); // 6 usable bits
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const int b = VP8YUVToB(y, u); // 5 usable bits
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const int rg = (r & 0xf8) | (g >> 5);
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const int gb = ((g << 3) & 0xe0) | (b >> 3);
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#ifdef WEBP_SWAP_16BIT_CSP
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rgb[0] = gb;
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rgb[1] = rg;
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#else
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rgb[0] = rg;
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rgb[1] = gb;
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#endif
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}
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static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const argb) {
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const int r = VP8YUVToR(y, v); // 4 usable bits
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const int g = VP8YUVToG(y, u, v); // 4 usable bits
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const int b = VP8YUVToB(y, u); // 4 usable bits
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const int rg = (r & 0xf0) | (g >> 4);
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const int ba = (b & 0xf0) | 0x0f; // overwrite the lower 4 bits
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#ifdef WEBP_SWAP_16BIT_CSP
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argb[0] = ba;
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argb[1] = rg;
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#else
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argb[0] = rg;
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argb[1] = ba;
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#endif
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}
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#else
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// Table-based version, not totally equivalent to the SSE2 version.
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// Rounding diff is only +/-1 though.
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extern int16_t VP8kVToR[256], VP8kUToB[256];
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extern int32_t VP8kVToG[256], VP8kUToG[256];
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@ -125,88 +214,11 @@ static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
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#endif
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}
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#else // Table-free version (slower on x86)
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// These constants are 16b fixed-point version of ITU-R BT.601 constants
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#define kYScale 76309 // 1.164 = 255 / 219
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#define kVToR 104597 // 1.596 = 255 / 112 * 0.701
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#define kUToG 25674 // 0.391 = 255 / 112 * 0.886 * 0.114 / 0.587
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#define kVToG 53278 // 0.813 = 255 / 112 * 0.701 * 0.299 / 0.587
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#define kUToB 132201 // 2.018 = 255 / 112 * 0.886
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#define kRCst (-kYScale * 16 - kVToR * 128 + YUV_HALF)
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#define kGCst (-kYScale * 16 + kUToG * 128 + kVToG * 128 + YUV_HALF)
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#define kBCst (-kYScale * 16 - kUToB * 128 + YUV_HALF)
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static WEBP_INLINE uint8_t VP8Clip8(int v) {
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return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> YUV_FIX)
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: (v < 0) ? 0u : 255u;
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}
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static WEBP_INLINE uint8_t VP8ClipN(int v, int N) { // clip to N bits
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return ((v & ~YUV_MASK) == 0) ? (uint8_t)(v >> (YUV_FIX + (8 - N)))
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: (v < 0) ? 0u : (255u >> (8 - N));
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}
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static WEBP_INLINE int VP8YUVToR(int y, int v) {
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return kYScale * y + kVToR * v + kRCst;
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}
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static WEBP_INLINE int VP8YUVToG(int y, int u, int v) {
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return kYScale * y - kUToG * u - kVToG * v + kGCst;
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}
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static WEBP_INLINE int VP8YUVToB(int y, int u) {
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return kYScale * y + kUToB * u + kBCst;
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}
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static WEBP_INLINE void VP8YuvToRgb(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const rgb) {
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rgb[0] = VP8Clip8(VP8YUVToR(y, v));
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rgb[1] = VP8Clip8(VP8YUVToG(y, u, v));
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rgb[2] = VP8Clip8(VP8YUVToB(y, u));
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}
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static WEBP_INLINE void VP8YuvToBgr(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const bgr) {
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bgr[0] = VP8Clip8(VP8YUVToB(y, u));
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bgr[1] = VP8Clip8(VP8YUVToG(y, u, v));
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bgr[2] = VP8Clip8(VP8YUVToR(y, v));
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}
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static WEBP_INLINE void VP8YuvToRgb565(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const rgb) {
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const int r = VP8Clip8(VP8YUVToR(y, u));
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const int g = VP8ClipN(VP8YUVToG(y, u, v), 6);
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const int b = VP8ClipN(VP8YUVToB(y, v), 5);
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const uint8_t rg = (r & 0xf8) | (g >> 3);
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const uint8_t gb = (g << 5) | b;
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#ifdef WEBP_SWAP_16BIT_CSP
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rgb[0] = gb;
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rgb[1] = rg;
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#else
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rgb[0] = rg;
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rgb[1] = gb;
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#endif
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}
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static WEBP_INLINE void VP8YuvToRgba4444(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const argb) {
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const int r = VP8Clip8(VP8YUVToR(y, u));
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const int g = VP8ClipN(VP8YUVToG(y, u, v), 4);
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const int b = VP8Clip8(VP8YUVToB(y, v));
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const uint8_t rg = (r & 0xf0) | g;
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const uint8_t ba = b | 0x0f; // overwrite the lower 4 bits
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#ifdef WEBP_SWAP_16BIT_CSP
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argb[0] = ba;
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argb[1] = rg;
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#else
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argb[0] = rg;
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argb[1] = ba;
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#endif
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}
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#endif // WEBP_YUV_USE_TABLE
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//-----------------------------------------------------------------------------
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// Alpha handling variants
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static WEBP_INLINE void VP8YuvToArgb(uint8_t y, uint8_t u, uint8_t v,
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uint8_t* const argb) {
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argb[0] = 0xff;
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@ -228,6 +240,28 @@ static WEBP_INLINE void VP8YuvToRgba(uint8_t y, uint8_t u, uint8_t v,
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// Must be called before everything, to initialize the tables.
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void VP8YUVInit(void);
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//-----------------------------------------------------------------------------
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// SSE2 extra functions (mostly for upsampling_sse2.c)
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#if defined(WEBP_USE_SSE2)
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#ifdef FANCY_UPSAMPLING
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// Process 32 pixels and store the result (24b or 32b per pixel) in *dst.
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extern void VP8YuvToRgba32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
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uint8_t* dst);
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extern void VP8YuvToRgb32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
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uint8_t* dst);
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extern void VP8YuvToBgra32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
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uint8_t* dst);
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extern void VP8YuvToBgr32(const uint8_t* y, const uint8_t* u, const uint8_t* v,
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uint8_t* dst);
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#endif // FANCY_UPSAMPLING
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// Must be called to initialize tables before using the functions.
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extern void VP8YUVInitSSE2(void);
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#endif // WEBP_USE_SSE2
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//------------------------------------------------------------------------------
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// RGB -> YUV conversion
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@ -257,7 +291,7 @@ static WEBP_INLINE int VP8RGBToV(int r, int g, int b) {
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#else
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// This JPEG-YUV colorspace, only for comparison!
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// These are also 16-bit precision coefficients from Rec.601, but with full
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// These are also 16bit precision coefficients from Rec.601, but with full
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// [0..255] output range.
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static WEBP_INLINE int VP8RGBToY(int r, int g, int b) {
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const int kRound = (1 << (YUV_FIX - 1));
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