audio – 如何将QBASIC PLAY命令转换为更现代的东西？

// file: play2wav.c
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>

#ifndef M_PI
#define M_PI 3.14159265358
#endif

double Note2Freq(int Note) // Note=1 = C1 (32.7032 Hz),Note=84 = B7 (3951.07 Hz)
{
  double f = 0;
  if (Note > 0)
    f = 440 * exp(log(2) * (Note - 46) / 12);
  return f;
}

int Name2SemitonesFromC(char c)
{
  static const int semitonesFromC[7] = { 9,11,2,4,5,7 }; // A,B,C,D,E,F,G
  if (c < 'A' && c > 'G') return -1;
  return semitonesFromC[c - 'A'];
}

typedef struct tPlayer
{
  enum
  {
    StateParsing,StateGenerating,} State;

  int Tempo;
  int Duration;
  int Octave;
  enum
  {
    ModeNormal,ModeLegato,ModeStaccato,} Mode;

  int Note;
  double NoteDuration;
  double NoteTime;
  unsigned SampleRate;
} tPlayer;

void PlayerInit(tPlayer* pPlayer,unsigned SampleRate)
{
  pPlayer->State = StateParsing;
  pPlayer->Tempo = 120; // [32,255] quarter notes per minute
  pPlayer->Duration = 4; // [1,64]
  pPlayer->Octave = 4; // [0,6]
  pPlayer->Mode = ModeNormal;
  pPlayer->Note = 0;
  pPlayer->SampleRate = SampleRate;
}

int PlayerGetSample(tPlayer* pPlayer,const char** ppMusicString,short* pSample)
{
  int number;
  int note = 0;
  int duration = 0;
  int dotCnt = 0;
  double sample;
  double freq;

  *pSample = 0;

  while (pPlayer->State == StateParsing)
  {
    char c = **ppMusicString;

    if (c == '') return 0;

    ++*ppMusicString;

    if (isspace(c)) continue;

    c = toupper(c);

    switch (c)
    {
    case 'O':
      c = **ppMusicString;
      if (c < '0' || c > '6') return 0;
      pPlayer->Octave = c - '0';
      ++*ppMusicString;
      break;

    case '<':
      if (pPlayer->Octave > 0) pPlayer->Octave--;
      break;

    case '>':
      if (pPlayer->Octave < 6) pPlayer->Octave++;
      break;

    case 'M':
      c = toupper(**ppMusicString);
      switch (c)
      {
      case 'L':
        pPlayer->Mode = ModeLegato;
        break;
      case 'N':
        pPlayer->Mode = ModeNormal;
        break;
      case 'S':
        pPlayer->Mode = ModeStaccato;
        break;
      case 'B':
      case 'F':
        // skip MB and MF
        break;
      default:
        return 0;
      }
      ++*ppMusicString;
      break; // ML/MN/MS,MB/MF

    case 'L':
    case 'T':
      number = 0;
      for (;;)
      {
        char c2 = **ppMusicString;
        if (isdigit(c2))
        {
          number = number * 10 + c2 - '0';
          ++*ppMusicString;
        }
        else break;
      }
      switch (c)
      {
      case 'L':
        if (number < 1 || number > 64) return 0;
        pPlayer->Duration = number;
        break;
      case 'T':
        if (number < 32 || number > 255) return 0;
        pPlayer->Tempo = number;
        break;
      }
      break; // Ln/Tn

    case 'A': case 'B': case 'C': case 'D':
    case 'E': case 'F': case 'G':
    case 'N':
    case 'P':
      switch (c)
      {
      case 'A': case 'B': case 'C': case 'D':
      case 'E': case 'F': case 'G':
        note = 1 + pPlayer->Octave * 12 + Name2SemitonesFromC(c);
        break; // A...G
      case 'P':
        note = 0;
        break; // P
      case 'N':
        number = 0;
        for (;;)
        {
          char c2 = **ppMusicString;
          if (isdigit(c2))
          {
            number = number * 10 + c2 - '0';
            ++*ppMusicString;
          }
          else break;
        }
        if (number < 0 || number > 84) return 0;
        note = number;
        break; // N
      } // got note #

      if (c >= 'A' && c <= 'G')
      {
        char c2 = **ppMusicString;
        if (c2 == '+' || c2 == '#')
        {
          if (note < 84) note++;
          ++*ppMusicString;
        }
        else if (c2 == '-')
        {
          if (note > 1) note--;
          ++*ppMusicString;
        }
      } // applied sharps and flats

      duration = pPlayer->Duration;

      if (c != 'N')
      {
        number = 0;
        for (;;)
        {
          char c2 = **ppMusicString;
          if (isdigit(c2))
          {
            number = number * 10 + c2 - '0';
            ++*ppMusicString;
          }
          else break;
        }
        if (number < 0 || number > 64) return 0;
        if (number > 0) duration = number;
      } // got note duration

      while (**ppMusicString == '.')
      {
        dotCnt++;
        ++*ppMusicString;
      } // got dots

      pPlayer->Note = note;
      pPlayer->NoteDuration = 1.0 / duration;
      while (dotCnt--)
      {
        duration *= 2;
        pPlayer->NoteDuration += 1.0 / duration;
      }
      pPlayer->NoteDuration *= 60 * 4. / pPlayer->Tempo; // in seconds now
      pPlayer->NoteTime = 0;

      pPlayer->State = StateGenerating;
      break; // A...G/N/P

    default:
      return 0;
    } // switch (c)
  }

  // pPlayer->State == StateGenerating
  // Calculate the next sample for the current note

  sample = 0;

  // QuickBasic Play() frequencies appear to be 1 octave higher than
  // on the piano.
  freq = Note2Freq(pPlayer->Note) * 2;

  if (freq > 0)
  {
    double f = freq;

    while (f < pPlayer->SampleRate / 2 && f < 8000) // Cap max frequency at 8 KHz
    {
      sample += exp(-0.125 * f / freq) * sin(2 * M_PI * f * pPlayer->NoteTime);
      f += 2 * freq; // Use only odd harmonics
    }

    sample *= 15000;
    sample *= exp(-pPlayer->NoteTime / 0.5); // Slow decay
  }

  if ((pPlayer->Mode == ModeNormal && pPlayer->NoteTime >= pPlayer->NoteDuration * 7 / 8) ||
      (pPlayer->Mode == ModeStaccato && pPlayer->NoteTime >= pPlayer->NoteDuration * 3 / 4))
    sample = 0;

  if (sample > 32767) sample = 32767;
  if (sample < -32767) sample = -32767;

  *pSample = (short)sample;

  pPlayer->NoteTime += 1.0 / pPlayer->SampleRate;

  if (pPlayer->NoteTime >= pPlayer->NoteDuration)
    pPlayer->State = StateParsing;

  return 1;
}

int PlayToFile(const char* pFileInName,const char* pFileOutName,unsigned SampleRate)
{
  int err = EXIT_FAILURE;
  FILE *fileIn = NULL,*fileOut = NULL;
  tPlayer player;
  short sample;
  char* pMusicString = NULL;
  const char* p;
  size_t sz = 1,len = 0;
  char c;
  unsigned char uc;
  unsigned long sampleCnt = 0,us;

  if ((fileIn = fopen(pFileInName,"rb")) == NULL)
  {
    fprintf(stderr,"can't open file "%s"n",pFileInName);
    goto End;
  }

  if ((fileOut = fopen(pFileOutName,"wb")) == NULL)
  {
    fprintf(stderr,"can't create file "%s"n",pFileOutName);
    goto End;
  }

  if ((pMusicString = malloc(sz)) == NULL)
  {
NoMemory:
    fprintf(stderr,"can't allocate memoryn");
    goto End;
  }

  // Load the input file into pMusicString[]

  while (fread(&c,1,fileIn))
  {
    pMusicString[len++] = c;

    if (len == sz)
    {
      char* p;

      sz *= 2;
      if (sz < len)
        goto NoMemory;

      p = realloc(pMusicString,sz);
      if (p == NULL)
        goto NoMemory;

      pMusicString = p;
    }
  }

  pMusicString[len] = ''; // Make pMusicString[] an ASCIIZ string

  // First,a dry run to simply count samples (needed for the WAV header)

  PlayerInit(&player,SampleRate);
  p = pMusicString;
  while (PlayerGetSample(&player,&p,&sample))
    sampleCnt++;

  if (p != pMusicString + len)
  {
    fprintf(stderr,"Parsing error near byte %u: "%c%c%c"n",(unsigned)(p - pMusicString),(p > pMusicString) ? p[-1] : ' ',p[0],(p - pMusicString + 1 < len) ? p[1] : ' ');
    goto End;
  }

  // Write the output file

  // ChunkID
  fwrite("RIFF",fileOut);

  // ChunkSize
  us = 36 + 2 * sampleCnt;
  uc = us % 256;
  fwrite(&uc,fileOut);
  uc = us / 256 % 256;
  fwrite(&uc,fileOut);
  uc = us / 256 / 256 % 256;
  fwrite(&uc,fileOut);
  uc = us / 256 / 256 / 256 % 256;
  fwrite(&uc,fileOut);

  // Format + Subchunk1ID
  fwrite("WAVEfmt ",8,fileOut);

  // Subchunk1Size
  uc = 16;
  fwrite(&uc,fileOut);
  uc = 0;
  fwrite(&uc,fileOut);
  fwrite(&uc,fileOut);

  // AudioFormat
  uc = 1;
  fwrite(&uc,fileOut);

  // NumChannels
  uc = 1;
  fwrite(&uc,fileOut);

  // SampleRate
  uc = SampleRate % 256;
  fwrite(&uc,fileOut);
  uc = SampleRate / 256 % 256;
  fwrite(&uc,fileOut);

  // ByteRate
  us = (unsigned long)SampleRate * 2;
  uc = us % 256;
  fwrite(&uc,fileOut);

  // BlockAlign
  uc = 2;
  fwrite(&uc,fileOut);

  // BitsPerSample
  uc = 16;
  fwrite(&uc,fileOut);

  // Subchunk2ID
  fwrite("data",fileOut);

  // Subchunk2Size
  us = sampleCnt * 2;
  uc = us % 256;
  fwrite(&uc,fileOut);

  // Data
  PlayerInit(&player,&sample))
  {
    uc = (unsigned)sample % 256;
    fwrite(&uc,fileOut);
    uc = (unsigned)sample / 256 % 256;
    fwrite(&uc,fileOut);
  }

  err = EXIT_SUCCESS;

End:

  if (pMusicString != NULL) free(pMusicString);
  if (fileOut != NULL) fclose(fileOut);
  if (fileIn != NULL) fclose(fileIn);

  return err;
}

int main(int argc,char** argv)
{
  if (argc == 3)
//    return PlayToFile(argv[1],argv[2],44100); // Use this for 44100 sample rate
    return PlayToFile(argv[1],16000);

  printf("Usage:n  play2wav <Input-QBASIC-Play-String-file> <Output-Wav-file>n");
  return EXIT_FAILURE;
}

用gcc编译：

gcc play2wav.c -o play2wav.exe

测试文件,JingleBells.txt：

t200l4o2mneel2el4eel2el4egl3cl8dl1el4ffl3fl8fl4fel2el8eel4edde
l2dgl4eel2el4eel2el4egl3cl8dl1el4ffl3fl8fl4fel2el8efl4ggfdl2c

跑：

play2wav.exe JingleBells.txt JingleBells.wav

喜欢听JingleBells.wav！