WavWriter.cc

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#include "WavWriter.hh"
#include "MSXException.hh"
#include "Math.hh"
#include "Mixer.hh"
#include "endian.hh"
#include "enumerate.hh"
#include "narrow.hh"
#include "one_of.hh"
#include "ranges.hh"
#include "vla.hh"
#include "xrange.hh"
#include <array>
#include <vector>
 
namespace openmsx {
 
WavWriter::WavWriter(const Filename& filename,
                     unsigned channels, unsigned bits, unsigned frequency)
        : file(filename, "wb")
{
        // write wav header
        struct WavHeader {
                std::array<char, 4> chunkID;       // + 0 'RIFF'
                Endian::L32         chunkSize;     // + 4 total size
                std::array<char, 4> format;        // + 8 'WAVE'
                std::array<char, 4> subChunk1ID;   // +12 'fmt '
                Endian::L32         subChunk1Size; // +16 = 16 (fixed)
                Endian::L16         audioFormat;   // +20 =  1 (fixed)
                Endian::L16         numChannels;   // +22
                Endian::L32         sampleRate;    // +24
                Endian::L32         byteRate;      // +28
                Endian::L16         blockAlign;    // +32
                Endian::L16         bitsPerSample; // +34
                std::array<char, 4> subChunk2ID;   // +36 'data'
                Endian::L32         subChunk2Size; // +40
        } header;
 
        ranges::copy(std::string_view("RIFF"), header.chunkID);
        header.chunkSize     = 0; // actual value filled in later
        ranges::copy(std::string_view("WAVE"), header.format);
        ranges::copy(std::string_view("fmt "), header.subChunk1ID);
        header.subChunk1Size = 16;
        header.audioFormat   = 1;
        header.numChannels   = narrow<uint16_t>(channels);
        header.sampleRate    = frequency;
        header.byteRate      = (channels * frequency * bits) / 8;
        header.blockAlign    = narrow<uint16_t>((channels * bits) / 8);
        header.bitsPerSample = narrow<uint16_t>(bits);
        ranges::copy(std::string_view("data"), header.subChunk2ID);
        header.subChunk2Size = 0; // actual value filled in later
 
        file.write(std::span{&header, 1});
}
 
WavWriter::~WavWriter()
{
        try {
                // data chunk must have an even number of bytes
                if (bytes & 1) {
                        std::array<uint8_t, 1> pad = {0};
                        file.write(pad);
                }
 
                flush(); // write header
        } catch (MSXException&) {
                // ignore, can't throw from destructor
        }
}
 
void WavWriter::flush()
{
        Endian::L32 totalSize = (bytes + 44 - 8 + 1) & ~1; // round up to even number
        Endian::L32 wavSize   = bytes;
 
        file.seek(4);
        file.write(std::span{&totalSize, 1});
        file.seek(40);
        file.write(std::span{&wavSize, 1});
        file.seek(file.getSize()); // SEEK_END
        file.flush();
}
 
void Wav8Writer::write(std::span<const uint8_t> buffer)
{
        file.write(buffer);
        bytes += narrow<uint32_t>(buffer.size_bytes());
}
 
void Wav16Writer::write(std::span<const int16_t> buffer)
{
        if constexpr (Endian::BIG) {
                // Variable length arrays (VLA) are part of c99 but not of c++
                // (not even c++11). Some compilers (like gcc) do support VLA
                // in c++ mode, others (like VC++) don't. Still other compilers
                // (like clang) only support VLA for POD types.
                // To side-step this issue we simply use a std::vector, this
                // code is anyway not performance critical.
                //VLA(Endian::L16, buf, samples); // doesn't work in clang
                std::vector<Endian::L16> buf(buffer.begin(), buffer.end());
                file.write(std::span{buf});
        } else {
                file.write(buffer);
        }
        bytes += narrow<uint32_t>(buffer.size_bytes());
}
 
static int16_t float2int16(float f)
{
        return Math::clipToInt16(lrintf(32768.0f * f));
}
 
void Wav16Writer::write(std::span<const float> buffer, float amp)
{
        std::vector<Endian::L16> buf_(buffer.size());
        std::span buf{buf_};
        ranges::transform(buffer, buf.data(), [=](float f) { return float2int16(f * amp); });
        file.write(buf);
        bytes += narrow<uint32_t>(buf.size_bytes());
}
 
void Wav16Writer::write(std::span<const StereoFloat> buffer, float ampLeft, float ampRight)
{
        std::vector<Endian::L16> buf(buffer.size() * 2);
        for (auto [i, s] : enumerate(buffer)) { // TODO use zip() in the future
                buf[2 * i + 0] = float2int16(s.left  * ampLeft);
                buf[2 * i + 1] = float2int16(s.right * ampRight);
        }
        std::span s{buf};
        file.write(s);
        bytes += narrow<uint32_t>(s.size_bytes());
}
 
void Wav16Writer::writeSilence(uint32_t samples)
{
        VLA(int16_t, buf, samples);
        ranges::fill(buf, 0);
        file.write(buf);
        bytes += narrow<uint32_t>(buf.size_bytes());
}
 
} // namespace openmsx