Deflicker.cc

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#include "Deflicker.hh"
#include "RawFrame.hh"
#include "PixelOperations.hh"
#include "unreachable.hh"
#include "vla.hh"
#include "build-info.hh"
#include <memory>
#ifdef __SSE2__
#include <emmintrin.h>
#endif

namespace openmsx {

template<typename Pixel> class DeflickerImpl final : public Deflicker
{
public:
        DeflickerImpl(const SDL_PixelFormat& format,
                      std::unique_ptr<RawFrame>* lastFrames);

private:
        const void* getLineInfo(
                unsigned line, unsigned& width,
                void* buf, unsigned bufWidth) const override;

        PixelOperations<Pixel> pixelOps;
};


std::unique_ptr<Deflicker> Deflicker::create(
        const SDL_PixelFormat& format,
        std::unique_ptr<RawFrame>* lastFrames)
{
#if HAVE_16BPP
        if (format.BitsPerPixel == 15 || format.BitsPerPixel == 16) {
                return std::make_unique<DeflickerImpl<uint16_t>>(format, lastFrames);
        }
#endif
#if HAVE_32BPP
        if (format.BitsPerPixel == 32) {
                return std::make_unique<DeflickerImpl<uint32_t>>(format, lastFrames);
        }
#endif
        UNREACHABLE; return nullptr; // avoid warning
}


Deflicker::Deflicker(const SDL_PixelFormat& format,
                     std::unique_ptr<RawFrame>* lastFrames_)
        : FrameSource(format)
        , lastFrames(lastFrames_)
{
}

void Deflicker::init()
{
        FrameSource::init(FIELD_NONINTERLACED);
        setHeight(lastFrames[0]->getHeight());
}

unsigned Deflicker::getLineWidth(unsigned line) const
{
        return lastFrames[0]->getLineWidthDirect(line);
}


template<typename Pixel>
DeflickerImpl<Pixel>::DeflickerImpl(const SDL_PixelFormat& format,
                                    std::unique_ptr<RawFrame>* lastFrames_)
        : Deflicker(format, lastFrames_)
        , pixelOps(format)
{
}

#ifdef __SSE2__
template<typename Pixel>
static __m128i blend(__m128i x, __m128i y, Pixel blendMask)
{
        if (sizeof(Pixel) == 4) {
                // 32bpp
                return _mm_avg_epu8(x, y);
        } else {
                // 16bpp,  (x & y) + (((x ^ y) & blendMask) >> 1)
                __m128i m = _mm_set1_epi16(blendMask);
                __m128i a = _mm_and_si128(x, y);
                __m128i b = _mm_xor_si128(x, y);
                __m128i c = _mm_and_si128(b, m);
                __m128i d = _mm_srli_epi16(c, 1);
                return _mm_add_epi16(a, d);
        }
}

template<typename Pixel>
static __m128i uload(const Pixel* ptr, ptrdiff_t byteOffst)
{
        auto* p8   = reinterpret_cast<const   char *>(ptr);
        auto* p128 = reinterpret_cast<const __m128i*>(p8 + byteOffst);
        return _mm_loadu_si128(p128);
}

template<typename Pixel>
static void ustore(Pixel* ptr, ptrdiff_t byteOffst, __m128i val)
{
        auto* p8   = reinterpret_cast<  char *>(ptr);
        auto* p128 = reinterpret_cast<__m128i*>(p8 + byteOffst);
        return _mm_storeu_si128(p128, val);
}

template<typename Pixel>
static __m128i compare(__m128i x, __m128i y)
{
        static_assert(sizeof(Pixel) == 4 || sizeof(Pixel) == 2);
        if (sizeof(Pixel) == 4) {
                return _mm_cmpeq_epi32(x, y);
        } else {
                return _mm_cmpeq_epi16(x, y);
        }
}
#endif

template<typename Pixel>
const void* DeflickerImpl<Pixel>::getLineInfo(
        unsigned line, unsigned& width, void* buf_, unsigned bufWidth) const
{
        unsigned width0 = lastFrames[0]->getLineWidthDirect(line);
        unsigned width1 = lastFrames[1]->getLineWidthDirect(line);
        unsigned width2 = lastFrames[2]->getLineWidthDirect(line);
        unsigned width3 = lastFrames[3]->getLineWidthDirect(line);
        const Pixel* line0 = lastFrames[0]->template getLinePtrDirect<Pixel>(line);
        const Pixel* line1 = lastFrames[1]->template getLinePtrDirect<Pixel>(line);
        const Pixel* line2 = lastFrames[2]->template getLinePtrDirect<Pixel>(line);
        const Pixel* line3 = lastFrames[3]->template getLinePtrDirect<Pixel>(line);
        if ((width0 != width3) || (width0 != width2) || (width0 != width1)) {
                // Not all the same width.
                width = width0;
                return line0;
        }

        // Prefer to write directly to the output buffer, if that's not
        // possible store the intermediate result in a temp buffer.
        VLA_SSE_ALIGNED(Pixel, buf2, width0);
        auto* buf = static_cast<Pixel*>(buf_);
        Pixel* out = (width0 <= bufWidth) ? buf : buf2;

        // Detect pixels that alternate between two different color values and
        // replace those with the average color. We search for an alternating
        // sequence with length (at least) 4. Or IOW we look for "A B A B".
        // The implementation below also detects a constant pixel value
        // "A A A A" as alternating between "A" and "A", but that's fine.
        Pixel* dst = out;
        unsigned remaining = width0;
#ifdef __SSE2__
        size_t pixelsPerSSE = sizeof(__m128i) / sizeof(Pixel);
        size_t widthSSE = remaining & ~(pixelsPerSSE - 1); // rounded down to a multiple of pixels in a SSE register
        line0 += widthSSE;
        line1 += widthSSE;
        line2 += widthSSE;
        line3 += widthSSE;
        dst   += widthSSE;
        auto byteOffst = -ptrdiff_t(widthSSE * sizeof(Pixel));

        Pixel blendMask = pixelOps.getBlendMask();
        while (byteOffst < 0) {
                __m128i a0 = uload(line0, byteOffst);
                __m128i a1 = uload(line1, byteOffst);
                __m128i a2 = uload(line2, byteOffst);
                __m128i a3 = uload(line3, byteOffst);

                __m128i e02 = compare<Pixel>(a0, a2); // a0 == a2
                __m128i e13 = compare<Pixel>(a1, a3); // a1 == a3
                __m128i cnd = _mm_and_si128(e02, e13); // (a0==a2) && (a1==a3)

                __m128i a01 = blend(a0, a1, blendMask);
                __m128i p = _mm_xor_si128(a0, a01);
                __m128i q = _mm_and_si128(p, cnd);
                __m128i r = _mm_xor_si128(q, a0); // select(a0, a01, cnd)

                ustore(dst, byteOffst, r);
                byteOffst += sizeof(__m128i);
        }
        remaining &= pixelsPerSSE - 1;
#endif
        for (unsigned x = 0; x < remaining; ++x) {
                dst[x] = ((line0[x] == line2[x]) && (line1[x] == line3[x]))
                       ? pixelOps.template blend<1, 1>(line0[x], line1[x])
                       : line0[x];
        }

        if (width0 <= bufWidth) {
                // It it already fits, we're done
                width = width0;
        } else {
                // Otherwise scale so that it does fit.
                width = bufWidth;
                scaleLine(out, buf, width0, bufWidth);
        }
        return buf;
}

} // namespace openmsx