WavWriter.cc

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#include "WavWriter.hh"
#include "MSXException.hh"
#include "Math.hh"
#include "endian.hh"
#include "one_of.hh"
#include "vla.hh"
#include "xrange.hh"
#include <cstring>
#include <vector>
 
namespace openmsx {
 
WavWriter::WavWriter(const Filename& filename,
                     unsigned channels, unsigned bits, unsigned frequency)
        : file(filename, "wb")
        , bytes(0)
{
        // write wav header
        struct WavHeader {
                char        chunkID[4];     // + 0 'RIFF'
                Endian::L32 chunkSize;      // + 4 total size
                char        format[4];      // + 8 'WAVE'
                char        subChunk1ID[4]; // +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
                char        subChunk2ID[4]; // +36 'data'
                Endian::L32 subChunk2Size;  // +40
        } header;
 
        memcpy(header.chunkID,     "RIFF", sizeof(header.chunkID));
        header.chunkSize     = 0; // actual value filled in later
        memcpy(header.format,      "WAVE", sizeof(header.format));
        memcpy(header.subChunk1ID, "fmt ", sizeof(header.subChunk1ID));
        header.subChunk1Size = 16;
        header.audioFormat   = 1;
        header.numChannels   = channels;
        header.sampleRate    = frequency;
        header.byteRate      = (channels * frequency * bits) / 8;
        header.blockAlign    = (channels * bits) / 8;
        header.bitsPerSample = bits;
        memcpy(header.subChunk2ID, "data", sizeof(header.subChunk2ID));
        header.subChunk2Size = 0; // actual value filled in later
 
        file.write(&header, sizeof(header));
}
 
WavWriter::~WavWriter()
{
        try {
                // data chunk must have an even number of bytes
                if (bytes & 1) {
                        uint8_t pad = 0;
                        file.write(&pad, 1);
                }
 
                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(&totalSize, 4);
        file.seek(40);
        file.write(&wavSize, 4);
        file.seek(file.getSize()); // SEEK_END
        file.flush();
}
 
void Wav8Writer::write(const uint8_t* buffer, unsigned samples)
{
        file.write(buffer, samples);
        bytes += samples;
}
 
void Wav16Writer::write(const int16_t* buffer, unsigned samples)
{
        unsigned size = sizeof(int16_t) * samples;
        if constexpr (OPENMSX_BIGENDIAN) {
                // 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, buffer + samples);
                file.write(buf.data(), size);
        } else {
                file.write(buffer, size);
        }
        bytes += size;
}
 
static int16_t float2int16(float f)
{
        return Math::clipIntToShort(lrintf(32768.0f * f));
}
 
void Wav16Writer::write(const float* buffer, unsigned stereo, unsigned samples,
                        float ampLeft, float ampRight)
{
        assert(stereo == one_of(1u, 2u));
        std::vector<Endian::L16> buf(samples * stereo);
        if (stereo == 1) {
                assert(ampLeft == ampRight);
                for (auto i : xrange(samples)) {
                        buf[i] = float2int16(buffer[i] * ampLeft);
                }
        } else {
                for (auto i : xrange(samples)) {
                        buf[2 * i + 0] = float2int16(buffer[2 * i + 0] * ampLeft);
                        buf[2 * i + 1] = float2int16(buffer[2 * i + 1] * ampRight);
                }
        }
        unsigned size = sizeof(int16_t) * samples * stereo;
        file.write(buf.data(), size);
        bytes += size;
}
 
void Wav16Writer::writeSilence(unsigned samples)
{
        VLA(int16_t, buf, samples);
        unsigned size = sizeof(int16_t) * samples;
        memset(buf, 0, size);
        file.write(buf, size);
        bytes += size;
}
 
} // namespace openmsx