dmusic.cpp

Go to the documentation of this file.

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#define INITGUID
#include "../stdafx.h"
#ifdef WIN32_LEAN_AND_MEAN
# undef WIN32_LEAN_AND_MEAN // Don't exclude rarely-used stuff from Windows headers
#endif
#include "../debug.h"
#include "../os/windows/win32.h"
#include "../core/mem_func.hpp"
#include "../thread.h"
#include "../fileio_func.h"
#include "../base_media_base.h"
#include "dmusic.h"
#include "midifile.hpp"
#include "midi.h"
 
#include <windows.h>
#include <dmksctrl.h>
#include <dmusicc.h>
#include <mutex>
 
#include "../safeguards.h"
 
#if defined(_MSC_VER)
# pragma comment(lib, "ole32.lib")
#endif /* defined(_MSC_VER) */
 
static const int MS_TO_REFTIME = 1000 * 10; 
static const int MIDITIME_TO_REFTIME = 10;  
 
 
#define FOURCC_INFO  mmioFOURCC('I', 'N', 'F', 'O')
#define FOURCC_fmt   mmioFOURCC('f', 'm', 't', ' ')
#define FOURCC_data  mmioFOURCC('d', 'a', 't', 'a')
 
struct DLSFile {
  struct DLSRegion {
    RGNHEADER hdr;
    WAVELINK wave;
    WSMPL wave_sample;
 
    std::vector<WLOOP> wave_loops;
    std::vector<CONNECTION> articulators;
  };
 
  struct DLSInstrument {
    INSTHEADER hdr;
 
    std::vector<CONNECTION> articulators;
    std::vector<DLSRegion> regions;
  };
 
  struct DLSWave {
    long file_offset;
 
    PCMWAVEFORMAT fmt;
    std::vector<BYTE> data;
 
    WSMPL wave_sample;
    std::vector<WLOOP> wave_loops;
 
    bool operator ==(long offset) const
    {
      return this->file_offset == offset;
    }
  };
 
  std::vector<DLSInstrument> instruments;
  std::vector<POOLCUE> pool_cues;
  std::vector<DLSWave> waves;
 
  bool LoadFile(const wchar_t *file);
 
private:
  bool ReadDLSArticulation(FILE *f, DWORD list_length, std::vector<CONNECTION> &out);
  bool ReadDLSRegionList(FILE *f, DWORD list_length, DLSInstrument &instrument);
  bool ReadDLSRegion(FILE *f, DWORD list_length, std::vector<DLSRegion> &out);
  bool ReadDLSInstrumentList(FILE *f, DWORD list_length);
  bool ReadDLSInstrument(FILE *f, DWORD list_length);
  bool ReadDLSWaveList(FILE *f, DWORD list_length);
  bool ReadDLSWave(FILE *f, DWORD list_length, long offset);
};
 
PACK_N(struct ChunkHeader {
  FOURCC type;  
  DWORD length; 
}, 2);
 
PACK_N(struct WAVE_DOWNLOAD {
  DMUS_DOWNLOADINFO   dlInfo;
  ULONG               ulOffsetTable[2];
  DMUS_WAVE           dmWave;
  DMUS_WAVEDATA       dmWaveData;
}, 2);
 
struct PlaybackSegment {
  uint32_t start, end;
  size_t start_block;
  bool loop;
};
 
static struct {
  bool shutdown;    
  bool playing;     
  bool do_start;    
  bool do_stop;     
 
  int preload_time; 
  byte new_volume;  
 
  MidiFile next_file;           
  PlaybackSegment next_segment; 
} _playback;
 
static std::thread _dmusic_thread;
static HANDLE _thread_event = nullptr;
static std::mutex _thread_mutex;
 
static IDirectMusic *_music = nullptr;
static IDirectMusicPort *_port = nullptr;
static IDirectMusicBuffer *_buffer = nullptr;
static std::vector<IDirectMusicDownload *> _dls_downloads;
 
 
static FMusicDriver_DMusic iFMusicDriver_DMusic;
 
 
bool DLSFile::ReadDLSArticulation(FILE *f, DWORD list_length, std::vector<CONNECTION> &out)
{
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_ART1) {
      CONNECTIONLIST conns;
      if (fread(&conns, sizeof(conns), 1, f) != 1) return false;
      fseek(f, conns.cbSize - sizeof(conns), SEEK_CUR);
 
      /* Read all defined articulations. */
      for (ULONG i = 0; i < conns.cConnections; i++) {
        CONNECTION con;
        if (fread(&con, sizeof(con), 1, f) != 1) return false;
        out.push_back(con);
      }
    } else {
      fseek(f, chunk.length, SEEK_CUR);
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSRegion(FILE *f, DWORD list_length, std::vector<DLSRegion> &out)
{
  out.push_back(DLSRegion());
  DLSRegion &region = out.back();
 
  /* Set default values. */
  region.wave_sample.cbSize = 0;
 
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      /* Unwrap list header. */
      if (fread(&chunk.type, sizeof(chunk.type), 1, f) != 1) return false;
      chunk.length -= sizeof(chunk.type);
    }
 
    switch (chunk.type) {
      case FOURCC_RGNH:
        if (fread(&region.hdr, sizeof(region.hdr), 1, f) != 1) return false;
        break;
 
      case FOURCC_WSMP:
        if (fread(&region.wave_sample, sizeof(region.wave_sample), 1, f) != 1) return false;
        fseek(f, region.wave_sample.cbSize - sizeof(region.wave_sample), SEEK_CUR);
 
        /* Read all defined sample loops. */
        for (ULONG i = 0; i < region.wave_sample.cSampleLoops; i++) {
          WLOOP loop;
          if (fread(&loop, sizeof(loop), 1, f) != 1) return false;
          region.wave_loops.push_back(loop);
        }
        break;
 
      case FOURCC_WLNK:
        if (fread(&region.wave, sizeof(region.wave), 1, f) != 1) return false;
        break;
 
      case FOURCC_LART: // List chunk
        if (!this->ReadDLSArticulation(f, chunk.length, region.articulators)) return false;
        break;
 
      case FOURCC_INFO:
        /* We don't care about info stuff. */
        fseek(f, chunk.length, SEEK_CUR);
        break;
 
      default:
        Debug(driver, 7, "DLS: Ignoring unknown chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
        fseek(f, chunk.length, SEEK_CUR);
        break;
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSRegionList(FILE *f, DWORD list_length, DLSInstrument &instrument)
{
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      FOURCC list_type;
      if (fread(&list_type, sizeof(list_type), 1, f) != 1) return false;
 
      if (list_type == FOURCC_RGN) {
        this->ReadDLSRegion(f, chunk.length - sizeof(list_type), instrument.regions);
      } else {
        Debug(driver, 7, "DLS: Ignoring unknown list chunk of type {}{}{}{}", (char)(list_type & 0xFF), (char)((list_type >> 8) & 0xFF), (char)((list_type >> 16) & 0xFF), (char)((list_type >> 24) & 0xFF));
        fseek(f, chunk.length - sizeof(list_type), SEEK_CUR);
      }
    } else {
      Debug(driver, 7, "DLS: Ignoring chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
      fseek(f, chunk.length, SEEK_CUR);
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSInstrument(FILE *f, DWORD list_length)
{
  this->instruments.push_back(DLSInstrument());
  DLSInstrument &instrument = this->instruments.back();
 
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      /* Unwrap list header. */
      if (fread(&chunk.type, sizeof(chunk.type), 1, f) != 1) return false;
      chunk.length -= sizeof(chunk.type);
    }
 
    switch (chunk.type) {
      case FOURCC_INSH:
        if (fread(&instrument.hdr, sizeof(instrument.hdr), 1, f) != 1) return false;
        break;
 
      case FOURCC_LART: // List chunk
        if (!this->ReadDLSArticulation(f, chunk.length, instrument.articulators)) return false;
        break;
 
      case FOURCC_LRGN: // List chunk
        if (!this->ReadDLSRegionList(f, chunk.length, instrument)) return false;
        break;
 
      case FOURCC_INFO:
        /* We don't care about info stuff. */
        fseek(f, chunk.length, SEEK_CUR);
        break;
 
      default:
        Debug(driver, 7, "DLS: Ignoring unknown chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
        fseek(f, chunk.length, SEEK_CUR);
        break;
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSInstrumentList(FILE *f, DWORD list_length)
{
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      FOURCC list_type;
      if (fread(&list_type, sizeof(list_type), 1, f) != 1) return false;
 
      if (list_type == FOURCC_INS) {
        Debug(driver, 6, "DLS: Reading instrument {}", (int)instruments.size());
 
        if (!this->ReadDLSInstrument(f, chunk.length - sizeof(list_type))) return false;
      } else {
        Debug(driver, 7, "DLS: Ignoring unknown list chunk of type {}{}{}{}", (char)(list_type & 0xFF), (char)((list_type >> 8) & 0xFF), (char)((list_type >> 16) & 0xFF), (char)((list_type >> 24) & 0xFF));
        fseek(f, chunk.length - sizeof(list_type), SEEK_CUR);
      }
    } else {
      Debug(driver, 7, "DLS: Ignoring chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
      fseek(f, chunk.length, SEEK_CUR);
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSWave(FILE *f, DWORD list_length, long offset)
{
  this->waves.push_back(DLSWave());
  DLSWave &wave = this->waves.back();
 
  /* Set default values. */
  MemSetT(&wave.wave_sample, 0);
  wave.wave_sample.cbSize = sizeof(WSMPL);
  wave.wave_sample.usUnityNote = 60;
  wave.file_offset = offset; // Store file offset so we can resolve the wave pool table later on.
 
  while (list_length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      /* Unwrap list header. */
      if (fread(&chunk.type, sizeof(chunk.type), 1, f) != 1) return false;
      chunk.length -= sizeof(chunk.type);
    }
 
    switch (chunk.type) {
      case FOURCC_fmt:
        if (fread(&wave.fmt, sizeof(wave.fmt), 1, f) != 1) return false;
        if (chunk.length > sizeof(wave.fmt)) fseek(f, chunk.length - sizeof(wave.fmt), SEEK_CUR);
        break;
 
      case FOURCC_WSMP:
        if (fread(&wave.wave_sample, sizeof(wave.wave_sample), 1, f) != 1) return false;
        fseek(f, wave.wave_sample.cbSize - sizeof(wave.wave_sample), SEEK_CUR);
 
        /* Read all defined sample loops. */
        for (ULONG i = 0; i < wave.wave_sample.cSampleLoops; i++) {
          WLOOP loop;
          if (fread(&loop, sizeof(loop), 1, f) != 1) return false;
          wave.wave_loops.push_back(loop);
        }
        break;
 
      case FOURCC_data:
        wave.data.resize(chunk.length);
        if (fread(&wave.data[0], sizeof(BYTE), wave.data.size(), f) != wave.data.size()) return false;
        break;
 
      case FOURCC_INFO:
        /* We don't care about info stuff. */
        fseek(f, chunk.length, SEEK_CUR);
        break;
 
      default:
        Debug(driver, 7, "DLS: Ignoring unknown chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
        fseek(f, chunk.length, SEEK_CUR);
        break;
    }
  }
 
  return true;
}
 
bool DLSFile::ReadDLSWaveList(FILE *f, DWORD list_length)
{
  long base_offset = ftell(f);
 
  while (list_length > 0) {
    long chunk_offset = ftell(f);
 
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    list_length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      FOURCC list_type;
      if (fread(&list_type, sizeof(list_type), 1, f) != 1) return false;
 
      if (list_type == FOURCC_wave) {
        Debug(driver, 6, "DLS: Reading wave {}", waves.size());
 
        if (!this->ReadDLSWave(f, chunk.length - sizeof(list_type), chunk_offset - base_offset)) return false;
      } else {
        Debug(driver, 7, "DLS: Ignoring unknown list chunk of type {}{}{}{}", (char)(list_type & 0xFF), (char)((list_type >> 8) & 0xFF), (char)((list_type >> 16) & 0xFF), (char)((list_type >> 24) & 0xFF));
        fseek(f, chunk.length - sizeof(list_type), SEEK_CUR);
      }
    } else {
      Debug(driver, 7, "DLS: Ignoring chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
      fseek(f, chunk.length, SEEK_CUR);
    }
  }
 
  return true;
}
 
bool DLSFile::LoadFile(const wchar_t *file)
{
  Debug(driver, 2, "DMusic: Try to load DLS file {}", FS2OTTD(file));
 
  FILE *f = _wfopen(file, L"rb");
  if (f == nullptr) return false;
 
  FileCloser f_scope(f);
 
  /* Check DLS file header. */
  ChunkHeader hdr;
  FOURCC dls_type;
  if (fread(&hdr, sizeof(hdr), 1, f) != 1) return false;
  if (fread(&dls_type, sizeof(dls_type), 1, f) != 1) return false;
  if (hdr.type != FOURCC_RIFF || dls_type != FOURCC_DLS) return false;
 
  hdr.length -= sizeof(FOURCC);
 
  Debug(driver, 2, "DMusic: Parsing DLS file");
 
  DLSHEADER header;
  MemSetT(&header, 0);
 
  /* Iterate over all chunks in the file. */
  while (hdr.length > 0) {
    ChunkHeader chunk;
    if (fread(&chunk, sizeof(chunk), 1, f) != 1) return false;
    hdr.length -= chunk.length + sizeof(chunk);
 
    if (chunk.type == FOURCC_LIST) {
      /* Unwrap list header. */
      if (fread(&chunk.type, sizeof(chunk.type), 1, f) != 1) return false;
      chunk.length -= sizeof(chunk.type);
    }
 
    switch (chunk.type) {
      case FOURCC_COLH:
        if (fread(&header, sizeof(header), 1, f) != 1) return false;
        break;
 
      case FOURCC_LINS: // List chunk
        if (!this->ReadDLSInstrumentList(f, chunk.length)) return false;
        break;
 
      case FOURCC_WVPL: // List chunk
        if (!this->ReadDLSWaveList(f, chunk.length)) return false;
        break;
 
      case FOURCC_PTBL:
        POOLTABLE ptbl;
        if (fread(&ptbl, sizeof(ptbl), 1, f) != 1) return false;
        fseek(f, ptbl.cbSize - sizeof(ptbl), SEEK_CUR);
 
        /* Read all defined cues. */
        for (ULONG i = 0; i < ptbl.cCues; i++) {
          POOLCUE cue;
          if (fread(&cue, sizeof(cue), 1, f) != 1) return false;
          this->pool_cues.push_back(cue);
        }
        break;
 
      case FOURCC_INFO:
        /* We don't care about info stuff. */
        fseek(f, chunk.length, SEEK_CUR);
        break;
 
      default:
        Debug(driver, 7, "DLS: Ignoring unknown chunk {}{}{}{}", (char)(chunk.type & 0xFF), (char)((chunk.type >> 8) & 0xFF), (char)((chunk.type >> 16) & 0xFF), (char)((chunk.type >> 24) & 0xFF));
        fseek(f, chunk.length, SEEK_CUR);
        break;
    }
  }
 
  /* Have we read as many instruments as indicated? */
  if (header.cInstruments != this->instruments.size()) return false;
 
  /* Resolve wave pool table. */
  for (std::vector<POOLCUE>::iterator cue = this->pool_cues.begin(); cue != this->pool_cues.end(); cue++) {
    std::vector<DLSWave>::iterator w = std::find(this->waves.begin(), this->waves.end(), cue->ulOffset);
    if (w != this->waves.end()) {
      cue->ulOffset = (ULONG)(w - this->waves.begin());
    } else {
      cue->ulOffset = 0;
    }
  }
 
  return true;
}
 
 
static byte ScaleVolume(byte original, byte scale)
{
  return original * scale / 127;
}
 
static void TransmitChannelMsg(IDirectMusicBuffer *buffer, REFERENCE_TIME rt, byte status, byte p1, byte p2 = 0)
{
  if (buffer->PackStructured(rt, 0, status | (p1 << 8) | (p2 << 16)) == E_OUTOFMEMORY) {
    /* Buffer is full, clear it and try again. */
    _port->PlayBuffer(buffer);
    buffer->Flush();
 
    buffer->PackStructured(rt, 0, status | (p1 << 8) | (p2 << 16));
  }
}
 
static void TransmitSysex(IDirectMusicBuffer *buffer, REFERENCE_TIME rt, const byte *&msg_start, size_t &remaining)
{
  /* Find end of message. */
  const byte *msg_end = msg_start;
  while (*msg_end != MIDIST_ENDSYSEX) msg_end++;
  msg_end++; // Also include SysEx end byte.
 
  if (buffer->PackUnstructured(rt, 0, msg_end - msg_start, const_cast<LPBYTE>(msg_start)) == E_OUTOFMEMORY) {
    /* Buffer is full, clear it and try again. */
    _port->PlayBuffer(buffer);
    buffer->Flush();
 
    buffer->PackUnstructured(rt, 0, msg_end - msg_start, const_cast<LPBYTE>(msg_start));
  }
 
  /* Update position in buffer. */
  remaining -= msg_end - msg_start;
  msg_start = msg_end;
}
 
static void TransmitStandardSysex(IDirectMusicBuffer *buffer, REFERENCE_TIME rt, MidiSysexMessage msg)
{
  size_t length = 0;
  const byte *data = MidiGetStandardSysexMessage(msg, length);
  TransmitSysex(buffer, rt, data, length);
}
 
static void TransmitNotesOff(IDirectMusicBuffer *buffer, REFERENCE_TIME block_time, REFERENCE_TIME cur_time)
{
  for (int ch = 0; ch < 16; ch++) {
    TransmitChannelMsg(buffer, block_time + 10, MIDIST_CONTROLLER | ch, MIDICT_MODE_ALLNOTESOFF, 0);
    TransmitChannelMsg(buffer, block_time + 10, MIDIST_CONTROLLER | ch, MIDICT_SUSTAINSW, 0);
    TransmitChannelMsg(buffer, block_time + 10, MIDIST_CONTROLLER | ch, MIDICT_MODE_RESETALLCTRL, 0);
  }
 
  /* Performing a GM reset stops all sound and resets all parameters. */
  TransmitStandardSysex(buffer, block_time + 20, MidiSysexMessage::ResetGM);
  TransmitStandardSysex(buffer, block_time + 30, MidiSysexMessage::RolandSetReverb);
 
  /* Explicitly flush buffer to make sure the messages are processed,
   * as we want sound to stop immediately. */
  _port->PlayBuffer(buffer);
  buffer->Flush();
 
  /* Wait until message time has passed. */
  Sleep(Clamp((block_time - cur_time) / MS_TO_REFTIME, 5, 1000));
}
 
static void MidiThreadProc()
{
  Debug(driver, 2, "DMusic: Entering playback thread");
 
  REFERENCE_TIME last_volume_time = 0; // timestamp of the last volume change
  REFERENCE_TIME block_time = 0;       // timestamp of the last block sent to the port
  REFERENCE_TIME playback_start_time;  // timestamp current file began playback
  MidiFile current_file;               // file currently being played from
  PlaybackSegment current_segment;     // segment info for current playback
  size_t current_block = 0;            // next block index to send
  byte current_volume = 0;             // current effective volume setting
  byte channel_volumes[16];            // last seen volume controller values in raw data
 
  /* Get pointer to the reference clock of our output port. */
  IReferenceClock *clock;
  _port->GetLatencyClock(&clock);
 
  REFERENCE_TIME cur_time;
  clock->GetTime(&cur_time);
 
  _port->PlayBuffer(_buffer);
  _buffer->Flush();
 
  DWORD next_timeout = 1000;
  while (true) {
    /* Wait for a signal from the GUI thread or until the time for the next event has come. */
    DWORD wfso = WaitForSingleObject(_thread_event, next_timeout);
 
    if (_playback.shutdown) {
      _playback.playing = false;
      break;
    }
 
    if (_playback.do_stop) {
      Debug(driver, 2, "DMusic thread: Stopping playback");
 
      /* Turn all notes off and wait a bit to allow the messages to be handled. */
      clock->GetTime(&cur_time);
      TransmitNotesOff(_buffer, block_time, cur_time);
 
      _playback.playing = false;
      _playback.do_stop = false;
      block_time = 0;
      next_timeout = 1000;
      continue;
    }
 
    if (wfso == WAIT_OBJECT_0) {
      if (_playback.do_start) {
        Debug(driver, 2, "DMusic thread: Starting playback");
        {
          /* New scope to limit the time the mutex is locked. */
          std::lock_guard<std::mutex> lock(_thread_mutex);
 
          current_file.MoveFrom(_playback.next_file);
          std::swap(_playback.next_segment, current_segment);
          current_segment.start_block = 0;
          current_block = 0;
          _playback.playing = true;
          _playback.do_start = false;
        }
 
        /* Reset playback device between songs. */
        clock->GetTime(&cur_time);
        TransmitNotesOff(_buffer, block_time, cur_time);
 
        MemSetT<byte>(channel_volumes, 127, lengthof(channel_volumes));
        /* Invalidate current volume. */
        current_volume = UINT8_MAX;
        last_volume_time = 0;
 
        /* Take the current time plus the preload time as the music start time. */
        clock->GetTime(&playback_start_time);
        playback_start_time += _playback.preload_time * MS_TO_REFTIME;
      }
    }
 
    if (_playback.playing) {
      /* skip beginning of file? */
      if (current_segment.start > 0 && current_block == 0 && current_segment.start_block == 0) {
        /* find first block after start time and pretend playback started earlier
         * this is to allow all blocks prior to the actual start to still affect playback,
         * as they may contain important controller and program changes */
        size_t preload_bytes = 0;
        for (size_t bl = 0; bl < current_file.blocks.size(); bl++) {
          MidiFile::DataBlock &block = current_file.blocks[bl];
          preload_bytes += block.data.size();
          if (block.ticktime >= current_segment.start) {
            if (current_segment.loop) {
              Debug(driver, 2, "DMusic: timer: loop from block {} (ticktime {}, realtime {:.3f}, bytes {})", bl, block.ticktime, ((int)block.realtime) / 1000.0, preload_bytes);
              current_segment.start_block = bl;
              break;
            } else {
              /* Skip the transmission delay compensation performed in the Win32 MIDI driver.
               * The DMusic driver will most likely be used with the MS softsynth, which is not subject to transmission delays.
               */
              Debug(driver, 2, "DMusic: timer: start from block {} (ticktime {}, realtime {:.3f}, bytes {})", bl, block.ticktime, ((int)block.realtime) / 1000.0, preload_bytes);
              playback_start_time -= block.realtime * MIDITIME_TO_REFTIME;
              break;
            }
          }
        }
      }
 
      /* Get current playback timestamp. */
      REFERENCE_TIME current_time;
      clock->GetTime(&current_time);
 
      /* Check for volume change. */
      if (current_volume != _playback.new_volume) {
        if (current_time - last_volume_time > 10 * MS_TO_REFTIME) {
          Debug(driver, 2, "DMusic thread: volume change");
          current_volume = _playback.new_volume;
          last_volume_time = current_time;
          for (int ch = 0; ch < 16; ch++) {
            int vol = ScaleVolume(channel_volumes[ch], current_volume);
            TransmitChannelMsg(_buffer, block_time + 1, MIDIST_CONTROLLER | ch, MIDICT_CHANVOLUME, vol);
          }
          _port->PlayBuffer(_buffer);
          _buffer->Flush();
        }
      }
 
      while (current_block < current_file.blocks.size()) {
        MidiFile::DataBlock &block = current_file.blocks[current_block];
 
        /* check that block isn't at end-of-song override */
        if (current_segment.end > 0 && block.ticktime >= current_segment.end) {
          if (current_segment.loop) {
            Debug(driver, 2, "DMusic thread: Looping song");
            current_block = current_segment.start_block;
            playback_start_time = current_time - current_file.blocks[current_block].realtime * MIDITIME_TO_REFTIME;
          } else {
            _playback.do_stop = true;
          }
          next_timeout = 0;
          break;
        }
        /* check that block is not in the future */
        REFERENCE_TIME playback_time = current_time - playback_start_time;
        if (block.realtime * MIDITIME_TO_REFTIME > playback_time +  3 *_playback.preload_time * MS_TO_REFTIME) {
          /* Stop the thread loop until we are at the preload time of the next block. */
          next_timeout = Clamp(((int64_t)block.realtime * MIDITIME_TO_REFTIME - playback_time) / MS_TO_REFTIME - _playback.preload_time, 0, 1000);
          Debug(driver, 9, "DMusic thread: Next event in {} ms (music {}, ref {})", next_timeout, block.realtime * MIDITIME_TO_REFTIME, playback_time);
          break;
        }
 
        /* Timestamp of the current block. */
        block_time = playback_start_time + block.realtime * MIDITIME_TO_REFTIME;
        Debug(driver, 9, "DMusic thread: Streaming block {} (cur={}, block={})", current_block, (long long)(current_time / MS_TO_REFTIME), (long long)(block_time / MS_TO_REFTIME));
 
        const byte *data = block.data.data();
        size_t remaining = block.data.size();
        byte last_status = 0;
        while (remaining > 0) {
          /* MidiFile ought to have converted everything out of running status,
           * but handle it anyway just to be safe */
          byte status = data[0];
          if (status & 0x80) {
            last_status = status;
            data++;
            remaining--;
          } else {
            status = last_status;
          }
          switch (status & 0xF0) {
            case MIDIST_PROGCHG:
            case MIDIST_CHANPRESS:
              /* 2 byte channel messages */
              TransmitChannelMsg(_buffer, block_time, status, data[0]);
              data++;
              remaining--;
              break;
            case MIDIST_NOTEOFF:
            case MIDIST_NOTEON:
            case MIDIST_POLYPRESS:
            case MIDIST_PITCHBEND:
              /* 3 byte channel messages */
              TransmitChannelMsg(_buffer, block_time, status, data[0], data[1]);
              data += 2;
              remaining -= 2;
              break;
            case MIDIST_CONTROLLER:
              /* controller change */
              if (data[0] == MIDICT_CHANVOLUME) {
                /* volume controller, adjust for user volume */
                channel_volumes[status & 0x0F] = data[1];
                int vol = ScaleVolume(data[1], current_volume);
                TransmitChannelMsg(_buffer, block_time, status, data[0], vol);
              } else {
                /* handle other controllers normally */
                TransmitChannelMsg(_buffer, block_time, status, data[0], data[1]);
              }
              data += 2;
              remaining -= 2;
              break;
            case 0xF0:
              /* system messages */
              switch (status) {
                case MIDIST_SYSEX: /* system exclusive */
                  TransmitSysex(_buffer, block_time, data, remaining);
                  break;
                case MIDIST_TC_QFRAME: /* time code quarter frame */
                case MIDIST_SONGSEL: /* song select */
                  data++;
                  remaining--;
                  break;
                case MIDIST_SONGPOSPTR: /* song position pointer */
                  data += 2;
                  remaining -= 2;
                  break;
                default: /* remaining have no data bytes */
                  break;
              }
              break;
          }
        }
 
        current_block++;
      }
 
      /* Anything in the playback buffer? Send it down the port. */
      DWORD used_buffer = 0;
      _buffer->GetUsedBytes(&used_buffer);
      if (used_buffer > 0) {
        _port->PlayBuffer(_buffer);
        _buffer->Flush();
      }
 
      /* end? */
      if (current_block == current_file.blocks.size()) {
        if (current_segment.loop) {
          current_block = current_segment.start_block;
          playback_start_time = block_time - current_file.blocks[current_block].realtime * MIDITIME_TO_REFTIME;
        } else {
          _playback.do_stop = true;
        }
        next_timeout = 0;
      }
    }
  }
 
  Debug(driver, 2, "DMusic: Exiting playback thread");
 
  /* Turn all notes off and wait a bit to allow the messages to be handled by real hardware. */
  clock->GetTime(&cur_time);
  TransmitNotesOff(_buffer, block_time, cur_time);
  Sleep(_playback.preload_time * 4);
 
  clock->Release();
}
 
static void * DownloadArticulationData(int base_offset, void *data, const std::vector<CONNECTION> &artic)
{
  DMUS_ARTICULATION2 *art = (DMUS_ARTICULATION2 *)data;
  art->ulArtIdx = base_offset + 1;
  art->ulFirstExtCkIdx = 0;
  art->ulNextArtIdx = 0;
 
  CONNECTIONLIST *con_list = (CONNECTIONLIST *)(art + 1);
  con_list->cbSize = sizeof(CONNECTIONLIST);
  con_list->cConnections = (ULONG)artic.size();
  MemCpyT((CONNECTION *)(con_list + 1), &artic.front(), artic.size());
 
  return (CONNECTION *)(con_list + 1) + artic.size();
}
 
static const char *LoadDefaultDLSFile(const char *user_dls)
{
  DMUS_PORTCAPS caps;
  MemSetT(&caps, 0);
  caps.dwSize = sizeof(DMUS_PORTCAPS);
  _port->GetCaps(&caps);
 
  /* Nothing to unless it is a synth with instrument download that doesn't come with GM voices by default. */
  if ((caps.dwFlags & (DMUS_PC_DLS | DMUS_PC_DLS2)) != 0 && (caps.dwFlags & DMUS_PC_GMINHARDWARE) == 0) {
    DLSFile dls_file;
 
    if (user_dls == nullptr) {
      /* Try loading the default GM DLS file stored in the registry. */
      HKEY hkDM;
      if (SUCCEEDED(RegOpenKeyEx(HKEY_LOCAL_MACHINE, L"Software\\Microsoft\\DirectMusic", 0, KEY_READ, &hkDM))) {
        wchar_t dls_path[MAX_PATH];
        DWORD buf_size = sizeof(dls_path); // Buffer size as to be given in bytes!
        if (SUCCEEDED(RegQueryValueEx(hkDM, L"GMFilePath", nullptr, nullptr, (LPBYTE)dls_path, &buf_size))) {
          wchar_t expand_path[MAX_PATH * 2];
          ExpandEnvironmentStrings(dls_path, expand_path, lengthof(expand_path));
          if (!dls_file.LoadFile(expand_path)) Debug(driver, 1, "Failed to load default GM DLS file from registry");
        }
        RegCloseKey(hkDM);
      }
 
      /* If we couldn't load the file from the registry, try again at the default install path of the GM DLS file. */
      if (dls_file.instruments.empty()) {
        static const wchar_t *DLS_GM_FILE = L"%windir%\\System32\\drivers\\gm.dls";
        wchar_t path[MAX_PATH];
        ExpandEnvironmentStrings(DLS_GM_FILE, path, lengthof(path));
 
        if (!dls_file.LoadFile(path)) return "Can't load GM DLS collection";
      }
    } else {
      if (!dls_file.LoadFile(OTTD2FS(user_dls).c_str())) return "Can't load GM DLS collection";
    }
 
    /* Get download port and allocate download IDs. */
    IDirectMusicPortDownload *download_port = nullptr;
    if (FAILED(_port->QueryInterface(IID_IDirectMusicPortDownload, (LPVOID *)&download_port))) return "Can't get download port";
 
    DWORD dlid_wave = 0, dlid_inst = 0;
    if (FAILED(download_port->GetDLId(&dlid_wave, (DWORD)dls_file.waves.size())) || FAILED(download_port->GetDLId(&dlid_inst, (DWORD)dls_file.instruments.size()))) {
      download_port->Release();
      return "Can't get enough DLS ids";
    }
 
    DWORD dwAppend = 0;
    download_port->GetAppend(&dwAppend);
 
    /* Download wave data. */
    for (DWORD i = 0; i < dls_file.waves.size(); i++) {
      IDirectMusicDownload *dl_wave = nullptr;
      if (FAILED(download_port->AllocateBuffer((DWORD)(sizeof(WAVE_DOWNLOAD) + dwAppend * dls_file.waves[i].fmt.wf.nBlockAlign + dls_file.waves[i].data.size()), &dl_wave))) {
        download_port->Release();
        return "Can't allocate wave download buffer";
      }
 
      WAVE_DOWNLOAD *wave;
      DWORD wave_size = 0;
      if (FAILED(dl_wave->GetBuffer((LPVOID *)&wave, &wave_size))) {
        dl_wave->Release();
        download_port->Release();
        return "Can't get wave download buffer";
      }
 
      /* Fill download data. */
      MemSetT(wave, 0);
      wave->dlInfo.dwDLType = DMUS_DOWNLOADINFO_WAVE;
      wave->dlInfo.cbSize = wave_size;
      wave->dlInfo.dwDLId = dlid_wave + i;
      wave->dlInfo.dwNumOffsetTableEntries = 2;
      wave->ulOffsetTable[0] = offsetof(WAVE_DOWNLOAD, dmWave);
      wave->ulOffsetTable[1] = offsetof(WAVE_DOWNLOAD, dmWaveData);
      wave->dmWave.ulWaveDataIdx = 1;
      MemCpyT((PCMWAVEFORMAT *)&wave->dmWave.WaveformatEx, &dls_file.waves[i].fmt, 1);
      wave->dmWaveData.cbSize = (DWORD)dls_file.waves[i].data.size();
      MemCpyT(wave->dmWaveData.byData, &dls_file.waves[i].data[0], dls_file.waves[i].data.size());
 
      _dls_downloads.push_back(dl_wave);
      if (FAILED(download_port->Download(dl_wave))) {
        download_port->Release();
        return "Downloading DLS wave failed";
      }
    }
 
    /* Download instrument data. */
    for (DWORD i = 0; i < dls_file.instruments.size(); i++) {
      DWORD offsets = 1 + (DWORD)dls_file.instruments[i].regions.size();
 
      /* Calculate download size for the instrument. */
      size_t i_size = sizeof(DMUS_DOWNLOADINFO) + sizeof(DMUS_INSTRUMENT);
      if (!dls_file.instruments[i].articulators.empty()) {
        /* Articulations are stored as two chunks, one containing meta data and one with the actual articulation data. */
        offsets += 2;
        i_size += sizeof(DMUS_ARTICULATION2) + sizeof(CONNECTIONLIST) + sizeof(CONNECTION) * dls_file.instruments[i].articulators.size();
      }
 
      for (std::vector<DLSFile::DLSRegion>::iterator rgn = dls_file.instruments[i].regions.begin(); rgn != dls_file.instruments[i].regions.end(); rgn++) {
        if (!rgn->articulators.empty()) {
          offsets += 2;
          i_size += sizeof(DMUS_ARTICULATION2) + sizeof(CONNECTIONLIST) + sizeof(CONNECTION) * rgn->articulators.size();
        }
 
        /* Region size depends on the number of wave loops. The size of the
         * declared structure already accounts for one loop. */
        if (rgn->wave_sample.cbSize != 0) {
          i_size += sizeof(DMUS_REGION) - sizeof(DMUS_REGION::WLOOP) + sizeof(WLOOP) * rgn->wave_loops.size();
        } else {
          i_size += sizeof(DMUS_REGION) - sizeof(DMUS_REGION::WLOOP) + sizeof(WLOOP) * dls_file.waves[dls_file.pool_cues[rgn->wave.ulTableIndex].ulOffset].wave_loops.size();
        }
      }
 
      i_size += offsets * sizeof(ULONG);
 
      /* Allocate download buffer. */
      IDirectMusicDownload *dl_inst = nullptr;
      if (FAILED(download_port->AllocateBuffer((DWORD)i_size, &dl_inst))) {
        download_port->Release();
        return "Can't allocate instrument download buffer";
      }
 
      void *instrument;
      DWORD inst_size = 0;
      if (FAILED(dl_inst->GetBuffer((LPVOID *)&instrument, &inst_size))) {
        dl_inst->Release();
        download_port->Release();
        return "Can't get instrument download buffer";
      }
      char *inst_base = (char *)instrument;
 
      /* Fill download header. */
      DMUS_DOWNLOADINFO *d_info = (DMUS_DOWNLOADINFO *)instrument;
      d_info->dwDLType = DMUS_DOWNLOADINFO_INSTRUMENT2;
      d_info->cbSize = inst_size;
      d_info->dwDLId = dlid_inst + i;
      d_info->dwNumOffsetTableEntries = offsets;
      instrument = d_info + 1;
 
      /* Download offset table; contains the offsets of all chunks relative to the buffer start. */
      ULONG *offset_table = (ULONG *)instrument;
      instrument = offset_table + offsets;
      int last_offset = 0;
 
      /* Instrument header. */
      DMUS_INSTRUMENT *inst_data = (DMUS_INSTRUMENT *)instrument;
      MemSetT(inst_data, 0);
      offset_table[last_offset++] = (char *)inst_data - inst_base;
      inst_data->ulPatch = (dls_file.instruments[i].hdr.Locale.ulBank & F_INSTRUMENT_DRUMS) | ((dls_file.instruments[i].hdr.Locale.ulBank & 0x7F7F) << 8) | (dls_file.instruments[i].hdr.Locale.ulInstrument & 0x7F);
      instrument = inst_data + 1;
 
      /* Write global articulations. */
      if (!dls_file.instruments[i].articulators.empty()) {
        inst_data->ulGlobalArtIdx = last_offset;
        offset_table[last_offset++] = (char *)instrument - inst_base;
        offset_table[last_offset++] = (char *)instrument + sizeof(DMUS_ARTICULATION2) - inst_base;
 
        instrument = DownloadArticulationData(inst_data->ulGlobalArtIdx, instrument, dls_file.instruments[i].articulators);
        assert((char *)instrument - inst_base <= (ptrdiff_t)inst_size);
      }
 
      /* Write out regions. */
      inst_data->ulFirstRegionIdx = last_offset;
      for (uint j = 0; j < dls_file.instruments[i].regions.size(); j++) {
        DLSFile::DLSRegion &rgn = dls_file.instruments[i].regions[j];
 
        DMUS_REGION *inst_region = (DMUS_REGION *)instrument;
        offset_table[last_offset++] = (char *)inst_region - inst_base;
        inst_region->RangeKey = rgn.hdr.RangeKey;
        inst_region->RangeVelocity = rgn.hdr.RangeVelocity;
        inst_region->fusOptions = rgn.hdr.fusOptions;
        inst_region->usKeyGroup = rgn.hdr.usKeyGroup;
        inst_region->ulFirstExtCkIdx = 0;
 
        ULONG wave_id = dls_file.pool_cues[rgn.wave.ulTableIndex].ulOffset;
        inst_region->WaveLink = rgn.wave;
        inst_region->WaveLink.ulTableIndex = wave_id + dlid_wave;
 
        /* The wave sample data will be taken from the region, if defined, otherwise from the wave itself. */
        if (rgn.wave_sample.cbSize != 0) {
          inst_region->WSMP = rgn.wave_sample;
          if (!rgn.wave_loops.empty()) MemCpyT(inst_region->WLOOP, &rgn.wave_loops.front(), rgn.wave_loops.size());
 
          instrument = (char *)(inst_region + 1) - sizeof(DMUS_REGION::WLOOP) + sizeof(WLOOP) * rgn.wave_loops.size();
        } else {
          inst_region->WSMP = rgn.wave_sample;
          if (!dls_file.waves[wave_id].wave_loops.empty()) MemCpyT(inst_region->WLOOP, &dls_file.waves[wave_id].wave_loops.front(), dls_file.waves[wave_id].wave_loops.size());
 
          instrument = (char *)(inst_region + 1) - sizeof(DMUS_REGION::WLOOP) + sizeof(WLOOP) * dls_file.waves[wave_id].wave_loops.size();
        }
 
        /* Write local articulator data. */
        if (!rgn.articulators.empty()) {
          inst_region->ulRegionArtIdx = last_offset;
          offset_table[last_offset++] = (char *)instrument - inst_base;
          offset_table[last_offset++] = (char *)instrument + sizeof(DMUS_ARTICULATION2) - inst_base;
 
          instrument = DownloadArticulationData(inst_region->ulRegionArtIdx, instrument, rgn.articulators);
        } else {
          inst_region->ulRegionArtIdx = 0;
        }
        assert((char *)instrument - inst_base <= (ptrdiff_t)inst_size);
 
        /* Link to the next region unless this was the last one.*/
        inst_region->ulNextRegionIdx = j < dls_file.instruments[i].regions.size() - 1 ? last_offset : 0;
      }
 
      _dls_downloads.push_back(dl_inst);
      if (FAILED(download_port->Download(dl_inst))) {
        download_port->Release();
        return "Downloading DLS instrument failed";
      }
    }
 
    download_port->Release();
  }
 
  return nullptr;
}
 
 
const char *MusicDriver_DMusic::Start(const StringList &parm)
{
  /* Initialize COM */
  if (FAILED(CoInitializeEx(nullptr, COINIT_MULTITHREADED))) return "COM initialization failed";
 
  /* Create the DirectMusic object */
  if (FAILED(CoCreateInstance(
        CLSID_DirectMusic,
        nullptr,
        CLSCTX_INPROC,
        IID_IDirectMusic,
        (LPVOID*)&_music
      ))) {
    return "Failed to create the music object";
  }
 
  /* Assign sound output device. */
  if (FAILED(_music->SetDirectSound(nullptr, nullptr))) return "Can't set DirectSound interface";
 
  /* MIDI events need to be send to the synth in time before their playback time
   * has come. By default, we try send any events at least 50 ms before playback. */
  _playback.preload_time = GetDriverParamInt(parm, "preload", 50);
 
  int pIdx = GetDriverParamInt(parm, "port", -1);
  if (_debug_driver_level > 0) {
    /* Print all valid output ports. */
    char desc[DMUS_MAX_DESCRIPTION];
 
    DMUS_PORTCAPS caps;
    MemSetT(&caps, 0);
    caps.dwSize = sizeof(DMUS_PORTCAPS);
 
    Debug(driver, 1, "Detected DirectMusic ports:");
    for (int i = 0; _music->EnumPort(i, &caps) == S_OK; i++) {
      if (caps.dwClass == DMUS_PC_OUTPUTCLASS) {
        Debug(driver, 1, " {}: {}{}", i, convert_from_fs(caps.wszDescription, desc, lengthof(desc)), i == pIdx ? " (selected)" : "");
      }
    }
  }
 
  GUID guidPort;
  if (pIdx >= 0) {
    /* Check if the passed port is a valid port. */
    DMUS_PORTCAPS caps;
    MemSetT(&caps, 0);
    caps.dwSize = sizeof(DMUS_PORTCAPS);
    if (FAILED(_music->EnumPort(pIdx, &caps))) return "Supplied port parameter is not a valid port";
    if (caps.dwClass != DMUS_PC_OUTPUTCLASS) return "Supplied port parameter is not an output port";
    guidPort = caps.guidPort;
  } else {
    if (FAILED(_music->GetDefaultPort(&guidPort))) return "Can't query default music port";
  }
 
  /* Create new port. */
  DMUS_PORTPARAMS params;
  MemSetT(&params, 0);
  params.dwSize = sizeof(DMUS_PORTPARAMS);
  params.dwValidParams = DMUS_PORTPARAMS_CHANNELGROUPS;
  params.dwChannelGroups = 1;
  if (FAILED(_music->CreatePort(guidPort, &params, &_port, nullptr))) return "Failed to create port";
  /* Activate port. */
  if (FAILED(_port->Activate(TRUE))) return "Failed to activate port";
 
  /* Create playback buffer. */
  DMUS_BUFFERDESC desc;
  MemSetT(&desc, 0);
  desc.dwSize = sizeof(DMUS_BUFFERDESC);
  desc.guidBufferFormat = KSDATAFORMAT_SUBTYPE_DIRECTMUSIC;
  desc.cbBuffer = 1024;
  if (FAILED(_music->CreateMusicBuffer(&desc, &_buffer, nullptr))) return "Failed to create music buffer";
 
  /* On soft-synths (e.g. the default DirectMusic one), we might need to load a wavetable set to get music. */
  const char *dls = LoadDefaultDLSFile(GetDriverParam(parm, "dls"));
  if (dls != nullptr) return dls;
 
  /* Create playback thread and synchronization primitives. */
  _thread_event = CreateEvent(nullptr, FALSE, FALSE, nullptr);
  if (_thread_event == nullptr) return "Can't create thread shutdown event";
 
  if (!StartNewThread(&_dmusic_thread, "ottd:dmusic", &MidiThreadProc)) return "Can't create MIDI output thread";
 
  return nullptr;
}
 
 
MusicDriver_DMusic::~MusicDriver_DMusic()
{
  this->Stop();
}
 
 
void MusicDriver_DMusic::Stop()
{
  if (_dmusic_thread.joinable()) {
    _playback.shutdown = true;
    SetEvent(_thread_event);
    _dmusic_thread.join();
  }
 
  /* Unloaded any instruments we loaded. */
  if (!_dls_downloads.empty()) {
    IDirectMusicPortDownload *download_port = nullptr;
    _port->QueryInterface(IID_IDirectMusicPortDownload, (LPVOID *)&download_port);
 
    /* Instruments refer to waves. As the waves are at the beginning of the download list,
     * do the unload from the back so that references are cleared properly. */
    for (std::vector<IDirectMusicDownload *>::reverse_iterator i = _dls_downloads.rbegin(); download_port != nullptr && i != _dls_downloads.rend(); i++) {
      download_port->Unload(*i);
      (*i)->Release();
    }
    _dls_downloads.clear();
 
    if (download_port != nullptr) download_port->Release();
  }
 
  if (_buffer != nullptr) {
    _buffer->Release();
    _buffer = nullptr;
  }
 
  if (_port != nullptr) {
    _port->Activate(FALSE);
    _port->Release();
    _port = nullptr;
  }
 
  if (_music != nullptr) {
    _music->Release();
    _music = nullptr;
  }
 
  CloseHandle(_thread_event);
 
  CoUninitialize();
}
 
 
void MusicDriver_DMusic::PlaySong(const MusicSongInfo &song)
{
  std::lock_guard<std::mutex> lock(_thread_mutex);
 
  if (!_playback.next_file.LoadSong(song)) return;
 
  _playback.next_segment.start = song.override_start;
  _playback.next_segment.end = song.override_end;
  _playback.next_segment.loop = song.loop;
 
  _playback.do_start = true;
  SetEvent(_thread_event);
}
 
 
void MusicDriver_DMusic::StopSong()
{
  _playback.do_stop = true;
  SetEvent(_thread_event);
}
 
 
bool MusicDriver_DMusic::IsSongPlaying()
{
  return _playback.playing || _playback.do_start;
}
 
 
void MusicDriver_DMusic::SetVolume(byte vol)
{
  _playback.new_volume = vol;
}