ZMBVEncoder.cc

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// Code based on DOSBox-0.65
 
#include "ZMBVEncoder.hh"
 
#include "FrameSource.hh"
#include "PixelOperations.hh"
 
#include "cstd.hh"
#include "endian.hh"
#include "narrow.hh"
#include "ranges.hh"
#include "unreachable.hh"
 
#include <array>
#include <bit>
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <tuple>
 
namespace openmsx {
 
static constexpr uint8_t DBZV_VERSION_HIGH = 0;
static constexpr uint8_t DBZV_VERSION_LOW = 1;
static constexpr uint8_t COMPRESSION_ZLIB = 1;
static constexpr unsigned MAX_VECTOR = 16;
static constexpr unsigned BLOCK_WIDTH  = MAX_VECTOR;
static constexpr unsigned BLOCK_HEIGHT = MAX_VECTOR;
static constexpr unsigned FLAG_KEYFRAME = 0x01;
 
struct CodecVector {
        int8_t x;
        int8_t y;
};
 
static constexpr unsigned VECTOR_TAB_SIZE =
        1 +                                       // center
        8 * MAX_VECTOR +                          // horizontal, vertical, diagonal
        MAX_VECTOR * MAX_VECTOR - 2 * MAX_VECTOR; // rest (only MAX_VECTOR/2)
 
static constexpr auto vectorTable = [] {
        std::array<CodecVector, VECTOR_TAB_SIZE> result = {};
 
        unsigned p = 0;
        // center
        result[p] = {0, 0};
        p += 1;
        // horizontal, vertical, diagonal
        for (int i = 1; i <= int(MAX_VECTOR); ++i, p += 8) {
                result[p + 0] = {int8_t( i), int8_t( 0)};
                result[p + 1] = {int8_t(-i), int8_t( 0)};
                result[p + 2] = {int8_t( 0), int8_t( i)};
                result[p + 3] = {int8_t( 0), int8_t(-i)};
                result[p + 4] = {int8_t( i), int8_t( i)};
                result[p + 5] = {int8_t(-i), int8_t( i)};
                result[p + 6] = {int8_t( i), int8_t(-i)};
                result[p + 7] = {int8_t(-i), int8_t(-i)};
        }
        // rest
        for (int y = 1; y <= int(MAX_VECTOR / 2); ++y) {
                for (int x = 1; x <= int(MAX_VECTOR / 2); ++x) {
                        if (x == y) continue; // already have diagonal
                        result[p + 0] = {int8_t( x), int8_t( y)};
                        result[p + 1] = {int8_t(-x), int8_t( y)};
                        result[p + 2] = {int8_t( x), int8_t(-y)};
                        result[p + 3] = {int8_t(-x), int8_t(-y)};
                        p += 4;
                }
        }
        assert(p == VECTOR_TAB_SIZE);
 
        // sort
        auto compare = [](const CodecVector& l, const CodecVector& r) {
                auto cost = [](const CodecVector& v) {
                        auto c = cstd::sqrt(double(v.x * v.x + v.y * v.y));
                        if ((v.x == 0) || (v.y == 0)) {
                                // no penalty for purely horizontal/vertical offset
                                c *= 1.0;
                        } else if (cstd::abs(v.x) == cstd::abs(v.y)) {
                                // small penalty for pure diagonal
                                c *= 2.0;
                        } else {
                                // bigger penalty for 'random' direction
                                c *= 4.0;
                        }
                        return c;
                };
                return std::tuple(cost(l), l.x, l.y) <
                       std::tuple(cost(r), r.x, r.y);
        };
        ranges::sort(result, compare);
 
        return result;
}();
 
struct KeyframeHeader {
        uint8_t high_version;
        uint8_t low_version;
        uint8_t compression;
        uint8_t format;
        uint8_t blockWidth;
        uint8_t blockHeight;
};
 
 
static inline void writePixel(
        unsigned pixel, Endian::L32& dest)
{
        PixelOperations pixelOps;
        unsigned r = pixelOps.red(pixel);
        unsigned g = pixelOps.green(pixel);
        unsigned b = pixelOps.blue(pixel);
        dest = (r << 16) | (g <<  8) |  b;
}
 
 
ZMBVEncoder::ZMBVEncoder(unsigned width_, unsigned height_)
        : width(width_)
        , height(height_)
{
        setupBuffers();
        memset(&zstream, 0, sizeof(zstream));
        deflateInit(&zstream, 6); // compression level
 
        // I did a small test: compression level vs compression speed
        //  (recorded Space Manbow intro, video only)
        //
        // level |  time  | size
        // ------+--------+----------
        //   0   | 1m12.6 | 139442594
        //   1   | 1m12.1 |   5217288
        //   2   | 1m10.8 |   4887258
        //   3   | 1m11.8 |   4610668
        //   4   | 1m13.1 |   3791932  <-- old default
        //   5   | 1m14.2 |   3602078
        //   6   | 1m14.5 |   3363766  <-- current default
        //   7   | 1m15.8 |   3333938
        //   8   | 1m25.0 |   3301168
        //   9   | 2m04.1 |   3253706
        //
        // Level 6 seems a good compromise between size/speed for THIS test.
}
 
void ZMBVEncoder::setupBuffers()
{
        static constexpr size_t pixelSize = sizeof(Pixel);
 
        pitch = width + 2 * MAX_VECTOR;
        auto bufSize = (height + 2 * MAX_VECTOR) * pitch * pixelSize + 2048;
 
        oldFrame.resize(bufSize);
        newFrame.resize(bufSize);
        ranges::fill(std::span{oldFrame.data(), bufSize}, 0);
        ranges::fill(std::span{newFrame.data(), bufSize}, 0);
        work.resize(bufSize);
        outputSize = neededSize();
        output.resize(outputSize);
 
        assert((width  % BLOCK_WIDTH ) == 0);
        assert((height % BLOCK_HEIGHT) == 0);
        size_t xBlocks = width / BLOCK_WIDTH;
        size_t yBlocks = height / BLOCK_HEIGHT;
        blockOffsets.resize(xBlocks * yBlocks);
        for (auto y : xrange(yBlocks)) {
                for (auto x : xrange(xBlocks)) {
                        blockOffsets[y * xBlocks + x] =
                                ((y * BLOCK_HEIGHT) + MAX_VECTOR) * pitch +
                                (x * BLOCK_WIDTH) + MAX_VECTOR;
                }
        }
}
 
unsigned ZMBVEncoder::neededSize() const
{
        static constexpr unsigned pixelSize = sizeof(Pixel);
        unsigned f = pixelSize * width * height + 2 * (1 + (width / 8)) * (1 + (height / 8)) + 1024;
        return f + f / 1000;
}
 
unsigned ZMBVEncoder::possibleBlock(int vx, int vy, size_t offset)
{
        int ret = 0;
        auto* pOld = &(std::bit_cast<Pixel*>(oldFrame.data()))[offset + (vy * pitch) + vx];
        auto* pNew = &(std::bit_cast<Pixel*>(newFrame.data()))[offset];
        for (unsigned y = 0; y < BLOCK_HEIGHT; y += 4) {
                for (unsigned x = 0; x < BLOCK_WIDTH; x += 4) {
                        if (pOld[x] != pNew[x]) ++ret;
                }
                pOld += pitch * 4;
                pNew += pitch * 4;
        }
        return ret;
}
 
unsigned ZMBVEncoder::compareBlock(int vx, int vy, size_t offset)
{
        int ret = 0;
        auto* pOld = &(std::bit_cast<Pixel*>(oldFrame.data()))[offset + (vy * pitch) + vx];
        auto* pNew = &(std::bit_cast<Pixel*>(newFrame.data()))[offset];
        repeat(BLOCK_HEIGHT, [&] {
                for (auto x : xrange(BLOCK_WIDTH)) {
                        if (pOld[x] != pNew[x]) ++ret;
                }
                pOld += pitch;
                pNew += pitch;
        });
        return ret;
}
 
void ZMBVEncoder::addXorBlock(int vx, int vy, size_t offset, unsigned& workUsed)
{
        using LE_P = typename Endian::Little<Pixel>::type;
 
        auto* pOld = &(std::bit_cast<Pixel*>(oldFrame.data()))[offset + (vy * pitch) + vx];
        auto* pNew = &(std::bit_cast<Pixel*>(newFrame.data()))[offset];
        repeat(BLOCK_HEIGHT, [&] {
                for (auto x : xrange(BLOCK_WIDTH)) {
                        auto pXor = pNew[x] ^ pOld[x];
                        writePixel(pXor, *std::bit_cast<LE_P*>(&work[workUsed]));
                        workUsed += sizeof(Pixel);
                }
                pOld += pitch;
                pNew += pitch;
        });
}
 
void ZMBVEncoder::addXorFrame(unsigned& workUsed)
{
        auto* vectors = std::bit_cast<int8_t*>(&work[workUsed]);
 
        unsigned xBlocks = width / BLOCK_WIDTH;
        unsigned yBlocks = height / BLOCK_HEIGHT;
        unsigned blockCount = xBlocks * yBlocks;
 
        // Align the following xor data on 4 byte boundary
        workUsed = (workUsed + blockCount * 2 + 3) & ~3;
 
        int bestVx = 0;
        int bestVy = 0;
        for (auto b : xrange(blockCount)) {
                auto offset = blockOffsets[b];
                // first try best vector of previous block
                unsigned bestChange = compareBlock(bestVx, bestVy, offset);
                if (bestChange >= 4) {
                        int possibles = 64;
                        for (const auto& v : vectorTable) {
                                if (possibleBlock(v.x, v.y, offset) < 4) {
                                        if (auto testChange = compareBlock(v.x, v.y, offset);
                                            testChange < bestChange) {
                                                bestChange = testChange;
                                                bestVx = narrow<int>(v.x);
                                                bestVy = narrow<int>(v.y);
                                                if (bestChange < 4) break;
                                        }
                                        --possibles;
                                        if (possibles == 0) break;
                                }
                        }
                }
                vectors[b * 2 + 0] = narrow<int8_t>(bestVx << 1);
                vectors[b * 2 + 1] = narrow<int8_t>(bestVy << 1);
                if (bestChange) {
                        vectors[b * 2 + 0] |= 1;
                        addXorBlock(bestVx, bestVy, offset, workUsed);
                }
        }
}
 
void ZMBVEncoder::addFullFrame(unsigned& workUsed)
{
        using LE_P = typename Endian::Little<Pixel>::type;
        static constexpr size_t pixelSize = sizeof(Pixel);
 
        auto* readFrame =
                &newFrame[pixelSize * (MAX_VECTOR + MAX_VECTOR * pitch)];
        repeat(height, [&] {
                auto* pixelsIn  = std::bit_cast<Pixel*>(readFrame);
                auto* pixelsOut = std::bit_cast<LE_P*>(&work[workUsed]);
                for (auto x : xrange(width)) {
                        writePixel(pixelsIn[x], pixelsOut[x]);
                }
                readFrame += pitch * sizeof(Pixel);
                workUsed += narrow<unsigned>(width * sizeof(Pixel));
        });
}
 
const ZMBVEncoder::Pixel* ZMBVEncoder::getScaledLine(const FrameSource* frame, unsigned y, Pixel* workBuf) const
{
        switch (height) {
        case 240:
                return frame->getLinePtr320_240(y, std::span<uint32_t, 320>(workBuf, 320)).data();
        case 480:
                return frame->getLinePtr640_480(y, std::span<uint32_t, 640>(workBuf, 640)).data();
        case 720:
                return frame->getLinePtr960_720(y, std::span<uint32_t, 960>(workBuf, 960)).data();
        default:
                UNREACHABLE;
        }
}
 
std::span<const uint8_t> ZMBVEncoder::compressFrame(bool keyFrame, const FrameSource* frame)
{
        std::swap(newFrame, oldFrame); // replace oldFrame with newFrame
 
        // Reset the work buffer
        unsigned workUsed = 0;
        unsigned writeDone = 1;
        uint8_t* writeBuf = output.data();
 
        output[0] = 0; // first byte contains info about this frame
        if (keyFrame) {
                static const uint8_t ZMBV_FORMAT_32BPP = 8;
 
                output[0] |= FLAG_KEYFRAME;
                auto* header = std::bit_cast<KeyframeHeader*>(
                        writeBuf + writeDone);
                header->high_version = DBZV_VERSION_HIGH;
                header->low_version = DBZV_VERSION_LOW;
                header->compression = COMPRESSION_ZLIB;
                header->format = ZMBV_FORMAT_32BPP;
                header->blockWidth = BLOCK_WIDTH;
                header->blockHeight = BLOCK_HEIGHT;
                writeDone += sizeof(KeyframeHeader);
                deflateReset(&zstream); // restart deflate
        }
 
        // copy lines (to add black border)
        static constexpr size_t pixelSize = sizeof(Pixel);
        auto linePitch = pitch * pixelSize;
        auto lineWidth = size_t(width) * pixelSize;
        uint8_t* dest =
                &newFrame[pixelSize * (MAX_VECTOR + MAX_VECTOR * pitch)];
        for (auto i : xrange(height)) {
                const auto* scaled = std::bit_cast<const uint8_t*>(
                        getScaledLine(frame, i, std::bit_cast<Pixel*>(dest)));
                if (scaled != dest) memcpy(dest, scaled, lineWidth);
                dest += linePitch;
        }
 
        // Add the frame data.
        if (keyFrame) {
                // Key frame: full frame data.
                addFullFrame(workUsed);
        } else {
                // Non-key frame: delta frame data.
                addXorFrame(workUsed);
        }
        // Compress the frame data with zlib.
        zstream.next_in = work.data();
        zstream.avail_in = workUsed;
        zstream.total_in = 0;
 
        zstream.next_out = std::bit_cast<Bytef*>(writeBuf + writeDone);
        zstream.avail_out = outputSize - writeDone;
        zstream.total_out = 0;
        auto r = deflate(&zstream, Z_SYNC_FLUSH);
        assert(r == Z_OK); (void)r;
 
        return {output.data(), writeDone + zstream.total_out};
}
 
} // namespace openmsx