用Direct Sound为MP3解码器libmad播放输出

1、用Direct Sound为MP3解码器libmad播放输出WIN32平台下madplay默认采用WaveOut播放输出，本文实现为其增加Direct Sound输出。在Windows XP，VC+ 6.0测试通过。 （一）优秀的MP3解码器libmad简介 libmad是跨平台的基于命令行的MP3播放解码器，使用定点解码，可用于没有浮点运算的嵌入式系统。 （二）下载及测试 1、从官方网站下载madplay-0.15.2b.tar.gz，libmad-0.15.1b.tar.gz，libid3tag-0.15.1b.tar.gz，还要从下载libz-1.

2、1.4.tar.gz，共四个文件。将四个压缩包保存在同一目录，例如d:madplay。 2、用WINRAR“解码压到当前目录”方法将四个压缩包解压，在d:madplay下将有四个文件夹：madplay-0.15.2b，libmad-0.15.1b，libid3tag-0.15.1b，libz-1.1.4。 3、用VC+ 6.0打开D:madplaymadplay-0.15.2bmsvc+下的madplay工程。修改VC+ 6.0的编译环境：Tools -> Options -> Directories标签 -> Directories框下增加如下两行： D

3、:MADPLAYLIBMAD-0.15.1BMSVC+ D:MADPLAYLIBID3TAG-0.15.1B 点击OK保存设置退出。再为编译连接后的可执行文件指定运行参数：Project -> settings -> 点中左侧madplay -> 右侧Program arguments框内填入你硬盘上保存的一个MP3文件，例如：D:MP3test.mp3，单击OK保存设置退出。 按Ctrl+F5编译连接运行，就可以听到播放你选择的MP3歌曲了。 (三）为madplay增加Direct Sound输出 madplay采用Wave

4、Out作为播放输出，用DS输出的优点不再我说了吧。 1、在audio.h中查找到“audio_ctlfunc_t audio_win32;”这一行，在下面增加一行： audio_ctlfunc_t audio_dsound; 2、在config.h中找到“#define AUDIO_DEFAULT audio_win32”这一行，将这一行注释掉，然后在下面增加一行： #define AUDIO_DEFAULT audio_dsound 3、在工作区中选择FileView标签，点击madplay files下的Source Files，添加文件a

5、duio_dsound.c 我写的aduio_dsound.c的内容如下，添加了比较详细的注释。   /* aduio_dsound.c功能: 用 Direct Sound 为MP3解码器libmad播放输出.兼容 VC+ 6.0 的directx 7.0接口函数: audio_dsound()email: (请注明主题 mp3 decoder)2008.08*/ /*libmad解码器头文件*/#include "audio.h" /*Direct Sound 的头文件和库*/#include<dsound

6、.h>#pragma comment( lib, "dsound.lib" ) /*高精定时器的头文件和库*/#include<mmsystem.h>#pragma comment( lib, "winmm.lib") /*DS_N: 缓冲区块数,设为8块.DS_ONEBUF: 一块的长度.设解码16帧的PCM数据长度,4608*16=73728(72KB).DS_BUFSIZE: Direct sound缓冲区长度,DS_N*DS_ONEBUF=589824(576KB).   

7、60;        最小4,最大0xfffffff,在dsound.h中由DSBSIZE_MIN和DSBSIZE_MAX定义.每一帧的时长26ms,一块的时间长度为26*16=416ms;缓冲区总时间长度8*416=3328ms.*/#define DS_N   8#define DS_ONEBUF  73728#define DS_BUFSIZE  589824 /*pcm_data - 暂存写入到时DSound Buffer的数据,该数据是由audio_pcm()解码M

8、P3帧得到的PCM数据,不同的解码器(如mpg123,libmad等)解码一帧的函数都采用向外部提供的接收缓冲区写入解码得到的PCM数据,将本模块略作改写可用于不同的MP3解码器播放输出.*/static unsigned char pcm_dataDS_ONEBUF+4608;static int pcm_length=0;static audio_pcmfunc_t *audio_pcm;static LPDIRECTSOUND   ds_lpDS=0;static LPDIRECTSOUNDBUFFER  ds_lpDSB=0;static HWND

9、0;  ds_hWndMain=0;static HANDLE  ds_hSemaphoreNotify=0;static DWORD  ds_dwWriteCursor=0;static DWORD  ds_dwPlayCursorOld=0;static MMRESULT  ds_timerID=0;static int   ds_iWriteTimes=0; /#define DBGOUTPUT #ifdef DBGOUTPUT  #include <stdio.h>#endi

10、f /*DirectSoundBuffer 通知机制引发的问题:若采用DirectSoundBuffer通知机制,发现运行其它使用相同通知机制的播放程序时,会造成本程序的通知事件误触发,如何识别是本程序还是其它程序引发的通知事件? 如何解决? 本程序采用定时器回调函数定时判断播放位置、发信号(设置通知事件).ds_dwWriteCursor: 写入光标,指向播放一块后释放的一个空闲块首址,跟随于播放光标后.ds_dwPlayCursor: 播放光标,取值(0.n)*DS_ONEBUF ds_dwPlayCursorOld: 暂存播放光标先前值,取值(0.n-1)*DS_ON

11、EBUF, 若使用写入光标,     由于本函数中“读”与audio_play()中“写”不同步而出错.*/ /*MyPlayPositionNotify()  - 定时器回调函数,播放完一块发一次信号.*/static void CALLBACKMyPlayPositionNotify(UINT uTimerID, UINT uMsg, DWORD dwUser, DWORD dw1, DWORD dw2) DWORD dwPlayCursor=0; ds_lpDSB->lpVtbl->GetCurr

12、entPosition(ds_lpDSB,&dwPlayCursor, NULL); if(dwPlayCursor>ds_dwPlayCursorOld+DS_ONEBUF |  (dwPlayCursor<DS_ONEBUF && ds_dwPlayCursorOld=DS_BUFSIZE-DS_ONEBUF) #ifdef DBGOUTPUT  printf("nWriteCursor = %6d, PlayCursor = %6d, PlayCursorOld = %6d",  &

13、#160; ds_dwWriteCursor, dwPlayCursor, ds_dwPlayCursorOld);#endif  dwPlayCursor /= DS_ONEBUF;  ds_dwPlayCursorOld = dwPlayCursor*DS_ONEBUF;   /* 发信号,使audio_play()内的等待函数返回. */  ReleaseSemaphore(ds_hSemaphoreNotify,1,NULL);  static int audio_open(int nChannels,long nS

14、amplesPerSec,unsigned int depth) DSBUFFERDESC dsbd; WAVEFORMATEX wvOut;  ds_dwWriteCursor=0; ds_dwPlayCursorOld=0; ds_iWriteTimes=0;  if(nSamplesPerSec = -1)  return -1;  /* Create DirectSound */ if ( DirectSoundCreate(NULL, &ds_lpDS, N

15、ULL) != DS_OK )   return -1;   if( ds_hWndMain = 0 )  ds_hWndMain=GetDesktopWindow();  /* Set Cooperative Level */ if ( ds_lpDS->lpVtbl->SetCooperativeLevel(ds_lpDS,ds_hWndMain, DSSCL_PRIORITY) != DS_OK )   return -1;   wvOut.wFormatT

16、ag      = WAVE_FORMAT_PCM; wvOut.wBitsPerSample  = depth; wvOut.nChannels       = nChannels; wvOut.nSamplesPerSec  = nSamplesPerSec; wvOut.nAvgBytesPerSec = wvOut.nSamplesPerSec * wvOut.nChannels * wvOut.wBitsPerSam

17、ple/8; wvOut.nBlockAlign     = wvOut.nChannels * wvOut.wBitsPerSample/8;  /* Create Secondary Sound Buffer */  ZeroMemory(&dsbd, sizeof(DSBUFFERDESC); dsbd.dwSize   = sizeof(DSBUFFERDESC); dsbd.dwFlags  = DSBCAPS_GLOBALFOCUS &

18、#160;     | DSBCAPS_CTRLVOLUME      | DSBCAPS_GETCURRENTPOSITION2; dsbd.dwBufferBytes = DS_BUFSIZE; dsbd.lpwfxFormat = &wvOut; if ( ds_lpDS->lpVtbl->CreateSoundBuffer(ds_lpDS,&dsbd, &ds_lpDSB, NULL) != DS_OK )   retur

19、n -1;   ds_hSemaphoreNotify = CreateSemaphore(NULL,DS_N,DS_N,NULL); if( ds_hSemaphoreNotify = NULL )  return -1;  return 0; /*audio_play() - 播放一块,每解码一帧被调用一次返回值: 写入到 SoundBuffer 的字节数,失败返回0*/static int audio_play(struct audio_play *play) LPVOID lpDSBuf;

20、0;DWORD dwDSLockSize; UINT len=0; HRESULT hr;  /* 1. 调用audio_pcm()解码一帧,得到的PCM写入到暂存区audio_pcm */  len = audio_pcm(pcm_data+pcm_length, play->nsamples,play->samples0,     play->samples1, play->mode, play->stats); pcm_length += len;&

21、#160;if (pcm_length < DS_ONEBUF)  return 0;  /* 2. 若audio_pcm已写满DS_ONEBUF字节,等待播放完一块后释放一个空闲块 */  WaitForSingleObject(ds_hSemaphoreNotify,INFINITE);  /* 3. 将audio_pcm写入到 SoundBuffer,使完成播放一块 */  hr = ds_lpDSB->lpVtbl->Lock(ds_lpDSB,ds_dwWriteCursor,

22、pcm_length,&lpDSBuf,&dwDSLockSize,NULL,0,0); if(hr = DSERR_BUFFERLOST)   ds_lpDSB->lpVtbl->Restore(ds_lpDSB);  ds_lpDSB->lpVtbl->Lock(ds_lpDSB,ds_dwWriteCursor,pcm_length,&lpDSBuf,&dwDSLockSize,NULL,0,0);  if(FAILED(hr)  return 0; CopyMe

23、mory(lpDSBuf,pcm_data,dwDSLockSize); ds_lpDSB->lpVtbl->Unlock(ds_lpDSB,lpDSBuf,dwDSLockSize,NULL,0);  /* 4. 更新相关变量! */  pcm_length=0; ds_dwWriteCursor += dwDSLockSize; if( ds_dwWriteCursor >= DS_BUFSIZE)  ds_dwWriteCursor -= DS_BUFSIZE;  /*

24、5. 首次写满Direct SoundBuffer后,启动定时器,开始播放 */  if(ds_iWriteTimes < DS_N)   ds_iWriteTimes+;  if(ds_iWriteTimes = DS_N)    UINT uRs = DS_ONEBUF / 4608 / 2 * 26;   ds_timerID = timeSetEvent( uRs/2, uRs, (LPTIMECALLBACK)MyPlayPositionNotify, 0,    &#

25、160;        TIME_PERIODIC | TIME_CALLBACK_FUNCTION );   ds_lpDSB->lpVtbl->SetCurrentPosition(ds_lpDSB,0);   ds_lpDSB->lpVtbl->Play(ds_lpDSB,0, 0, DSBPLAY_LOOPING);  #ifdef DBGOUTPUT  printf("nWriteTimes= %2d, WriteByte

26、s= %d",ds_iWriteTimes,dwDSLockSize);#endif   return dwDSLockSize; static int audio_init(struct audio_init *init)  SetPriorityClass(GetCurrentProcess(), HIGH_PRIORITY_CLASS);  SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_HIGHEST);   return 0; 

27、;static int audio_config(struct audio_config *config)  unsigned int bitdepth;   bitdepth = config->precision & 7;  if (bitdepth = 0)    bitdepth = 16;  else if (bitdepth > 32)    bitdepth = 32;   audio_close();   if

28、 (audio_open(config->channels,config->speed, bitdepth) = -1)   return -1;   switch (config->precision = bitdepth)   case 8:    audio_pcm = audio_pcm_u8;    break;   case 16:    audio_pcm = audio_pcm_s16le; 

29、   break;   case 24:    audio_pcm = audio_pcm_s24le;    break;   case 32:    audio_pcm = audio_pcm_s32le;    break;     return 0; static int audio_pause(int bPause) static int paused;&#

30、160;if(ds_lpDSB = 0)  return -1; if (bPause && !paused)   ds_lpDSB->lpVtbl->Stop(ds_lpDSB);  return 0;  else if (!bPause && paused)   ds_lpDSB->lpVtbl->Play(ds_lpDSB,0, 0, DSBPLAY_LOOPING);  return 0;   paused = bPaus

31、e; return 0; static int audio_stop() if(ds_lpDSB = 0)  return -1; ds_lpDSB->lpVtbl->Stop(ds_lpDSB); return 0; /*audio_flush() - 播放完Direct Sound缓冲区ds_lpDSB中的数据,DS_N-1块*/static void audio_flush() int i; for( i=1; i<DS_N; i+ )  WaitForSingleObj

32、ect(ds_hSemaphoreNotify,INFINITE); static int audio_close() SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_NORMAL); SetPriorityClass(GetCurrentProcess(), NORMAL_PRIORITY_CLASS);  if (ds_lpDSB != 0)   ds_lpDSB->lpVtbl->Stop(ds_lpDSB);  ds_lpDSB->lpVtbl->Release(ds_lpDSB);  ds_lpDSB = 0;  if (ds_timerID != 0)   timeKillEvent(ds_timerID);  ds_t