static WEBP_INLINE uint32_t ClampedAddSubtractHalf(const uint32_t* const c0,
const uint32_t* const c1,
const uint32_t* const c2) {
const uint8x8_t p0 = vreinterpret_u8_u64(vcreate_u64(*c0));
const uint8x8_t p1 = vreinterpret_u8_u64(vcreate_u64(*c1));
const uint8x8_t p2 = vreinterpret_u8_u64(vcreate_u64(*c2));
const uint8x8_t avg = vhadd_u8(p0, p1); // Average(c0,c1)
const uint8x8_t ab = vshr_n_u8(vqsub_u8(avg, p2), 1); // (a-b)>>1 saturated
const uint8x8_t ba = vshr_n_u8(vqsub_u8(p2, avg), 1); // (b-a)>>1 saturated
const uint8x8_t out = vqsub_u8(vqadd_u8(avg, ab), ba);
return vget_lane_u32(vreinterpret_u32_u8(out), 0);
}
static WEBP_INLINE uint32_t ClampedAddSubtractHalf(const uint32_t* const c0,
const uint32_t* const c1,
const uint32_t* const c2) {
const uint64x1_t C0 = { *c0, 0 }, C1 = { *c1, 0 }, C2 = { *c2, 0 };
const uint8x8_t p0 = vreinterpret_u8_u64(C0);
const uint8x8_t p1 = vreinterpret_u8_u64(C1);
const uint8x8_t p2 = vreinterpret_u8_u64(C2);
const uint8x8_t avg = vhadd_u8(p0, p1); // Average(c0,c1)
const uint8x8_t ab = vshr_n_u8(vqsub_u8(avg, p2), 1); // (a-b)>>1 saturated
const uint8x8_t ba = vshr_n_u8(vqsub_u8(p2, avg), 1); // (b-a)>>1 saturated
const uint8x8_t out = vqsub_u8(vqadd_u8(avg, ab), ba);
uint32_t ret;
vst1_lane_u32(&ret, vreinterpret_u32_u8(out), 0);
return ret;
}
bool decode_yuv_neon(unsigned char* out, unsigned char const* y, unsigned char const* uv, int width, int height, unsigned char fill_alpha=0xff)
{
// pre-condition : width, height must be even
if (0!=(width&1) || width<2 || 0!=(height&1) || height<2 || !out || !y || !uv)
return false;
// in & out pointers
unsigned char* dst = out;
// constants
int const stride = width*trait::bytes_per_pixel;
int const itHeight = height>>1;
int const itWidth = width>>3;
uint8x8_t const Yshift = vdup_n_u8(16);
int16x8_t const half = vdupq_n_u16(128);
int32x4_t const rounding = vdupq_n_s32(128);
// tmp variable
uint16x8_t t;
// pixel block to temporary store 8 pixels
typename trait::PixelBlock pblock = trait::init_pixelblock(fill_alpha);
for (int j=0; j<itHeight; ++j, y+=width, dst+=stride) {
for (int i=0; i<itWidth; ++i, y+=8, uv+=8, dst+=(8*trait::bytes_per_pixel)) {
t = vmovl_u8(vqsub_u8(vld1_u8(y), Yshift));
int32x4_t const Y00 = vmulq_n_u32(vmovl_u16(vget_low_u16(t)), 298);
int32x4_t const Y01 = vmulq_n_u32(vmovl_u16(vget_high_u16(t)), 298);
t = vmovl_u8(vqsub_u8(vld1_u8(y+width), Yshift));
int32x4_t const Y10 = vmulq_n_u32(vmovl_u16(vget_low_u16(t)), 298);
int32x4_t const Y11 = vmulq_n_u32(vmovl_u16(vget_high_u16(t)), 298);
// trait::loadvu pack 4 sets of uv into a uint8x8_t, layout : { v0,u0, v1,u1, v2,u2, v3,u3 }
t = vsubq_s16((int16x8_t)vmovl_u8(trait::loadvu(uv)), half);
// UV.val[0] : v0, v1, v2, v3
// UV.val[1] : u0, u1, u2, u3
int16x4x2_t const UV = vuzp_s16(vget_low_s16(t), vget_high_s16(t));
// tR : 128+409V
// tG : 128-100U-208V
// tB : 128+516U
int32x4_t const tR = vmlal_n_s16(rounding, UV.val[0], 409);
int32x4_t const tG = vmlal_n_s16(vmlal_n_s16(rounding, UV.val[0], -208), UV.val[1], -100);
int32x4_t const tB = vmlal_n_s16(rounding, UV.val[1], 516);
int32x4x2_t const R = vzipq_s32(tR, tR); // [tR0, tR0, tR1, tR1] [ tR2, tR2, tR3, tR3]
int32x4x2_t const G = vzipq_s32(tG, tG); // [tG0, tG0, tG1, tG1] [ tG2, tG2, tG3, tG3]
int32x4x2_t const B = vzipq_s32(tB, tB); // [tB0, tB0, tB1, tB1] [ tB2, tB2, tB3, tB3]
// upper 8 pixels
trait::store_pixel_block(dst, pblock,
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(R.val[0], Y00)), vqmovun_s32(vaddq_s32(R.val[1], Y01))), 8),
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(G.val[0], Y00)), vqmovun_s32(vaddq_s32(G.val[1], Y01))), 8),
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(B.val[0], Y00)), vqmovun_s32(vaddq_s32(B.val[1], Y01))), 8));
// lower 8 pixels
trait::store_pixel_block(dst+stride, pblock,
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(R.val[0], Y10)), vqmovun_s32(vaddq_s32(R.val[1], Y11))), 8),
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(G.val[0], Y10)), vqmovun_s32(vaddq_s32(G.val[1], Y11))), 8),
vshrn_n_u16(vcombine_u16(vqmovun_s32(vaddq_s32(B.val[0], Y10)), vqmovun_s32(vaddq_s32(B.val[1], Y11))), 8));
}
}
return true;
}
inline uint8x8_t vqsub(const uint8x8_t & v0, const uint8x8_t & v1) { return vqsub_u8 (v0, v1); }
