CasImage.cc

Go to the documentation of this file.

#include "CasImage.hh"
 
#include "File.hh"
#include "FilePool.hh"
#include "Filename.hh"
#include "CliComm.hh"
#include "MSXException.hh"
 
#include "narrow.hh"
#include "ranges.hh"
#include "stl.hh"
#include "xrange.hh"
 
#include <memory>
#include <span>
 
static constexpr std::array<uint8_t, 10> ASCII_HEADER  = { 0xEA,0xEA,0xEA,0xEA,0xEA,0xEA,0xEA,0xEA,0xEA,0xEA };
static constexpr std::array<uint8_t, 10> BINARY_HEADER = { 0xD0,0xD0,0xD0,0xD0,0xD0,0xD0,0xD0,0xD0,0xD0,0xD0 };
static constexpr std::array<uint8_t, 10> BASIC_HEADER  = { 0xD3,0xD3,0xD3,0xD3,0xD3,0xD3,0xD3,0xD3,0xD3,0xD3 };
// parsing code assumes these all have the same size
static_assert(ASCII_HEADER.size() == BINARY_HEADER.size());
static_assert(ASCII_HEADER.size() == BASIC_HEADER.size());
 
namespace openmsx {
 
// We oversample the audio signal for better sound quality (especially in
// combination with the hq resampler). Without oversampling the audio output
// could contain portions like this:
//   -1, +1, -1, +1, -1, +1, ...
// So it contains a signal at the Nyquist frequency. The hq resampler contains
// a low-pass filter, and (all practically implementable) filters cut off a
// portion of the spectrum near the Nyquist freq. So this high freq signal was
// lost after the hq resampler. After oversampling, the signal looks like this:
//   -1, -1, -1, -1, +1, +1, +1, +1, -1, -1, -1, -1, ...
// So every sample repeated 4 times.
static constexpr unsigned AUDIO_OVERSAMPLE = 4;
 
static void append(std::vector<int8_t>& wave, size_t count, int8_t value)
{
        wave.insert(wave.end(), count, value);
}
 
static void writeSilence(std::vector<int8_t>& wave, unsigned s)
{
        append(wave, s, 0);
}
 
static bool compare(const uint8_t* p, std::span<const uint8_t> rhs)
{
        return ranges::equal(std::span{p, rhs.size()}, rhs);
}
 
namespace MSX_CAS {
 
// a higher baudrate doesn't work anymore, but it is unclear why, because 4600
// baud should work (known from Speedsave 4000 and Turbo 5000 programs).
// 3765 still works on a Toshiba HX-10 and Philips NMS 8250, but not on a
// Panasonic FS-A1WSX, on which 3763 is the max. National CF-2000 has 3762 as
// the max. Let's take 3760 then as a safe value.
// UPDATE: that seems to break RUN"CAS:" type of programs. 3744 seems to work
// for those as well (we don't understand why yet)
static constexpr unsigned BAUDRATE = 3744;
static constexpr unsigned OUTPUT_FREQUENCY = 4 * BAUDRATE; // 4 samples per bit
 
// number of output bytes for silent parts
static constexpr unsigned SHORT_SILENCE = OUTPUT_FREQUENCY * 1; // 1 second
static constexpr unsigned LONG_SILENCE  = OUTPUT_FREQUENCY * 2; // 2 seconds
 
// number of 1-bits for headers
static constexpr unsigned LONG_HEADER  = 16000 / 2;
static constexpr unsigned SHORT_HEADER =  4000 / 2;
 
// headers definitions
static constexpr std::array<uint8_t, 8> CAS_HEADER = { 0x1F,0xA6,0xDE,0xBA,0xCC,0x13,0x7D,0x74 };
 
static void write0(std::vector<int8_t>& wave)
{
        static constexpr std::array<int8_t, 4> chunk{127, 127, -127, -127};
        ::append(wave, chunk);
}
static void write1(std::vector<int8_t>& wave)
{
        static constexpr std::array<int8_t, 4> chunk{127, -127, 127, -127};
        ::append(wave, chunk);
}
 
static void writeHeader(std::vector<int8_t>& wave, unsigned s)
{
        repeat(s, [&] { write1(wave); });
}
 
static void writeByte(std::vector<int8_t>& wave, uint8_t b)
{
        // one start bit
        write0(wave);
        // eight data bits
        for (auto i : xrange(8)) {
                if (b & (1 << i)) {
                        write1(wave);
                } else {
                        write0(wave);
                }
        }
        // two stop bits
        write1(wave);
        write1(wave);
}
 
// write data until a header is detected
static bool writeData(std::vector<int8_t>& wave, std::span<const uint8_t> cas, size_t& pos)
{
        bool eof = false;
        while ((pos + CAS_HEADER.size()) <= cas.size()) {
                if (compare(&cas[pos], CAS_HEADER)) {
                        return eof;
                }
                writeByte(wave, cas[pos]);
                if (cas[pos] == 0x1A) {
                        eof = true;
                }
                pos++;
        }
        while (pos < cas.size()) {
                writeByte(wave, cas[pos++]);
        }
        return false;
}
 
static CasImage::Data convert(std::span<const uint8_t> cas, const std::string& filename, CliComm& cliComm,
                              CassetteImage::FileType& firstFileType)
{
        CasImage::Data data;
        data.frequency = OUTPUT_FREQUENCY;
        auto& wave = data.wave;
 
        // search for a header in the .cas file
        bool issueWarning = false;
        bool headerFound = false;
        bool firstFile = true;
        size_t pos = 0;
        while ((pos + CAS_HEADER.size()) <= cas.size()) {
                if (compare(&cas[pos], CAS_HEADER)) {
                        // it probably works fine if a long header is used for every
                        // header but since the msx bios makes a distinction between
                        // them, we do also (hence a lot of code).
                        headerFound = true;
                        pos += CAS_HEADER.size();
                        writeSilence(wave, LONG_SILENCE);
                        writeHeader(wave, LONG_HEADER);
                        if ((pos + ASCII_HEADER.size()) <= cas.size()) {
                                // determine file type
                                auto type = [&] {
                                        if (compare(&cas[pos], ASCII_HEADER)) {
                                                return CassetteImage::ASCII;
                                        } else if (compare(&cas[pos], BINARY_HEADER)) {
                                                return CassetteImage::BINARY;
                                        } else if (compare(&cas[pos], BASIC_HEADER)) {
                                                return CassetteImage::BASIC;
                                        } else {
                                                return CassetteImage::UNKNOWN;
                                        }
                                }();
                                if (firstFile) firstFileType = type;
                                switch (type) {
                                        case CassetteImage::ASCII:
                                                writeData(wave, cas, pos);
                                                do {
                                                        pos += CAS_HEADER.size();
                                                        writeSilence(wave, SHORT_SILENCE);
                                                        writeHeader(wave, SHORT_HEADER);
                                                        bool eof = writeData(wave, cas, pos);
                                                        if (eof) break;
                                                } while ((pos + CAS_HEADER.size()) <= cas.size());
                                                break;
                                        case CassetteImage::BINARY:
                                        case CassetteImage::BASIC:
                                                writeData(wave, cas, pos);
                                                writeSilence(wave, SHORT_SILENCE);
                                                writeHeader(wave, SHORT_HEADER);
                                                pos += CAS_HEADER.size();
                                                writeData(wave, cas, pos);
                                                break;
                                        default:
                                                // unknown file type: using long header
                                                writeData(wave, cas, pos);
                                                break;
                                }
                        } else {
                                // unknown file type: using long header
                                writeData(wave, cas, pos);
                        }
                        firstFile = false;
                } else {
                        // skipping unhandled data, shouldn't occur in normal cas file
                        pos++;
                        issueWarning = true;
                }
        }
        if (!headerFound) {
                throw MSXException(filename, ": not a valid CAS image");
        }
        if (issueWarning) {
                 cliComm.printWarning("Skipped unhandled data in ", filename);
        }
 
        return data;
}
 
} // namespace MSX_CAS
 
namespace SVI_CAS {
 
static constexpr std::array<uint8_t, 17> header = {
        0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
        0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55,
        0x7f,
};
 
static void writeBit(std::vector<int8_t>& wave, bool bit)
{
        size_t count = bit ? 1 : 2;
        append(wave, count,  127);
        append(wave, count, -127);
}
 
static void writeByte(std::vector<int8_t>& wave, uint8_t byte)
{
        for (int i = 7; i >= 0; --i) {
                writeBit(wave, (byte >> i) & 1);
        }
}
 
static void processBlock(std::span<const uint8_t> subBuf, std::vector<int8_t>& wave)
{
        writeSilence(wave, 1200);
        writeBit(wave, true);
        repeat(199, [&] { writeByte(wave, 0x55); });
        writeByte(wave, 0x7f);
        for (uint8_t val : subBuf) {
                writeBit(wave, false);
                writeByte(wave, val);
        }
}
 
static CasImage::Data convert(std::span<const uint8_t> cas, CassetteImage::FileType& firstFileType)
{
        CasImage::Data data;
        data.frequency = 4800;
 
        if (cas.size() >= (header.size() + ASCII_HEADER.size())) {
                if (compare(&cas[header.size()], ASCII_HEADER)) {
                        firstFileType = CassetteImage::ASCII;
                } else if (compare(&cas[header.size()], BINARY_HEADER)) {
                        firstFileType = CassetteImage::BINARY;
                } else if (compare(&cas[header.size()], BASIC_HEADER)) {
                        firstFileType = CassetteImage::BASIC;
                }
        }
 
        auto prevHeader = cas.begin() + header.size();
        while (true) {
                auto nextHeader = std::search(prevHeader, cas.end(),
                                              header.begin(), header.end());
                processBlock(std::span(prevHeader, nextHeader), data.wave);
                if (nextHeader == cas.end()) break;
                prevHeader = nextHeader + header.size();
        }
        return data;
}
 
} // namespace SVI_CAS
 
CasImage::Data CasImage::init(const Filename& filename, FilePool& filePool, CliComm& cliComm)
{
        File file(filename);
        auto cas = file.mmap();
 
        auto fileType = CassetteImage::UNKNOWN;
        auto result = [&] {
                if ((cas.size() >= SVI_CAS::header.size()) &&
                    (compare(cas.data(), SVI_CAS::header))) {
                        return SVI_CAS::convert(cas, fileType);
                } else {
                        return MSX_CAS::convert(cas, filename.getOriginal(), cliComm, fileType);
                }
        }();
        setFirstFileType(fileType);
 
        // conversion successful, now calc sha1sum
        setSha1Sum(filePool.getSha1Sum(file));
 
        return result;
}
 
CasImage::CasImage(const Filename& filename, FilePool& filePool, CliComm& cliComm)
        : data(init(filename, filePool, cliComm))
{
}
 
int16_t CasImage::getSampleAt(EmuTime::param time) const
{
        EmuDuration d = time - EmuTime::zero();
        unsigned pos = d.getTicksAt(data.frequency);
        return narrow<int16_t>((pos < data.wave.size()) ? (data.wave[pos] * 256) : 0);
}
 
EmuTime CasImage::getEndTime() const
{
        EmuDuration d = EmuDuration::hz(data.frequency) * data.wave.size();
        return EmuTime::zero() + d;
}
 
unsigned CasImage::getFrequency() const
{
        return data.frequency * AUDIO_OVERSAMPLE;
}
 
void CasImage::fillBuffer(unsigned pos, std::span<float*, 1> bufs, unsigned num) const
{
        size_t nbSamples = data.wave.size();
        if ((pos / AUDIO_OVERSAMPLE) < nbSamples) {
                for (auto i : xrange(num)) {
                        bufs[0][i] = ((pos / AUDIO_OVERSAMPLE) < nbSamples)
                                   ? narrow_cast<float>(data.wave[pos / AUDIO_OVERSAMPLE])
                                   : 0.0f;
                        ++pos;
                }
        } else {
                bufs[0] = nullptr;
        }
}
 
float CasImage::getAmplificationFactorImpl() const
{
        return 1.0f / 128.0f;
}
 
} // namespace openmsx