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用Direct Sound為MP3解碼器libmad播放輸出 收藏
WIN32平臺下madplay默認(rèn)采用WaveOut播放輸出，本文實(shí)現(xiàn)為其增加Direct Sound輸出。在Windows XP，VC++ 6.0測試通過。 （一）優(yōu)秀的MP3解碼器libmad簡介
libmad是跨平臺的基于命令行的MP3播放解碼器，使用定點(diǎn)解碼，可用于沒有浮點(diǎn)運(yùn)算的嵌入式系統(tǒng)。
（二）下載及測試
1、從官方網(wǎng)站ftp://ftp.mars.org/pub/mpeg/下載madplay-0.15.2b.tar.gz，libmad-0.15.1b.tar.gz，libid3tag-0.15.1b.tar.gz，還要從ftp://ftp.mars.org/pub/mpeg/extra/下載libz-1.1.4.tar.gz，共四個(gè)文件。將四個(gè)壓縮包保存在同一目錄，例如d:\madplay。
2、用WINRAR“解碼壓到當(dāng)前目錄”方法將四個(gè)壓縮包解壓，在d:\madplay下將有四個(gè)文件夾：madplay-0.15.2b，libmad-0.15.1b，libid3tag-0.15.1b，libz-1.1.4。
3、用VC++ 6.0打開D:\madplay\madplay-0.15.2b\msvc++下的madplay工程。修改VC++ 6.0的編譯環(huán)境：Tools -> Options -> Directories標(biāo)簽 -> Directories框下增加如下兩行：
D:\MADPLAY\LIBMAD-0.15.1B\MSVC++
D:\MADPLAY\LIBID3TAG-0.15.1B
點(diǎn)擊OK保存設(shè)置退出。再為編譯連接后的可執(zhí)行文件指定運(yùn)行參數(shù)：Project -> settings -> 點(diǎn)中左側(cè)madplay -> 右側(cè)Program arguments框內(nèi)填入你硬盤上保存的一個(gè)MP3文件，例如：D:\MP3\test.mp3，單擊OK保存設(shè)置退出。
按Ctrl+F5編譯連接運(yùn)行，就可以聽到播放你選擇的MP3歌曲了。
(三）為madplay增加Direct Sound輸出
madplay采用WaveOut作為播放輸出，用DS輸出的優(yōu)點(diǎn)不再我說了吧。
1、在audio.h中查找到“audio_ctlfunc_t audio_win32;”這一行，在下面增加一行：
audio_ctlfunc_t audio_dsound;
2、在config.h中找到“#define AUDIO_DEFAULT audio_win32”這一行，將這一行注釋掉，然后在下面增加一行：
#define AUDIO_DEFAULT audio_dsound
3、在工作區(qū)中選擇FileView標(biāo)簽，點(diǎn)擊madplay files下的Source Files，添加文件aduio_dsound.c
我寫的aduio_dsound.c的內(nèi)容如下，添加了比較詳細(xì)的注釋。
/*
aduio_dsound.c 功能: 用 Direct Sound 為MP3解碼器libmad播放輸出.兼容 VC++ 6.0 的directx 7.0 接口函數(shù): audio_dsound() email: ly2697@sina.com (請注明主題 mp3 decoder) 2008.08 */ /*
libmad解碼器頭文件 */ #include "audio.h" /*
Direct Sound 的頭文件和庫 */ #include<dsound.h> #pragma comment( lib, "dsound.lib" ) /*
高精定時(shí)器的頭文件和庫 */ #include<mmsystem.h> #pragma comment( lib, "winmm.lib") /*
DS_N: 緩沖區(qū)塊數(shù),設(shè)為8塊. DS_ONEBUF: 一塊的長度.設(shè)解碼16幀的PCM數(shù)據(jù)長度,4608*16=73728(72KB). DS_BUFSIZE: Direct sound緩沖區(qū)長度,DS_N*DS_ONEBUF=589824(576KB). 最小4,最大0xfffffff,在dsound.h中由DSBSIZE_MIN和DSBSIZE_MAX定義. 每一幀的時(shí)長26ms,一塊的時(shí)間長度為26*16=416ms;緩沖區(qū)總時(shí)間長度8*416=3328ms. */ #define DS_N 8 #define DS_ONEBUF 73728 #define DS_BUFSIZE 589824 /*
pcm_data[] -- 暫存寫入到時(shí)DSound Buffer的數(shù)據(jù),該數(shù)據(jù)是由audio_pcm()解碼MP3幀得 到的PCM數(shù)據(jù),不同的解碼器(如mpg123,libmad等)解碼一幀的函數(shù)都采用向外部提供的接收 緩沖區(qū)寫入解碼得到的PCM數(shù)據(jù),將本模塊略作改寫可用于不同的MP3解碼器播放輸出. */ static unsigned char pcm_data[DS_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 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> #endif /*
DirectSoundBuffer 通知機(jī)制引發(fā)的問題: 若采用DirectSoundBuffer通知機(jī)制,發(fā)現(xiàn)運(yùn)行其它使用相同通知機(jī)制的播放程序時(shí),會造成 本程序的通知事件誤觸發(fā),如何識別是本程序還是其它程序引發(fā)的通知事件? 如何解決? 本程序采用定時(shí)器回調(diào)函數(shù)定時(shí)判斷播放位置、發(fā)信號(設(shè)置通知事件).
ds_dwWriteCursor: 寫入光標(biāo),指向播放一塊后釋放的一個(gè)空閑塊首址,跟隨于播放光標(biāo)后. ds_dwPlayCursor: 播放光標(biāo),取值(0..n)*DS_ONEBUF ds_dwPlayCursorOld: 暫存播放光標(biāo)先前值,取值(0..n-1)*DS_ONEBUF, 若使用寫入光標(biāo), 由于本函數(shù)中“讀”與audio_play()中“寫”不同步而出錯(cuò). */ /*
MyPlayPositionNotify() -- 定時(shí)器回調(diào)函數(shù),播放完一塊發(fā)一次信號. */ static void CALLBACK MyPlayPositionNotify(UINT uTimerID, UINT uMsg, DWORD dwUser, DWORD dw1, DWORD dw2) { DWORD dwPlayCursor=0; ds_lpDSB->lpVtbl->GetCurrentPosition(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", ds_dwWriteCursor, dwPlayCursor, ds_dwPlayCursorOld); #endif dwPlayCursor /= DS_ONEBUF; ds_dwPlayCursorOld = dwPlayCursor*DS_ONEBUF; /* 發(fā)信號,使audio_play()內(nèi)的等待函數(shù)返回. */
ReleaseSemaphore(ds_hSemaphoreNotify,1,NULL); } } static int audio_open(int nChannels,long nSamplesPerSec,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, NULL) != 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.wFormatTag = WAVE_FORMAT_PCM;
wvOut.wBitsPerSample = depth; wvOut.nChannels = nChannels; wvOut.nSamplesPerSec = nSamplesPerSec; wvOut.nAvgBytesPerSec = wvOut.nSamplesPerSec * wvOut.nChannels * wvOut.wBitsPerSample/8; wvOut.nBlockAlign = wvOut.nChannels * wvOut.wBitsPerSample/8; /* Create Secondary Sound Buffer */
ZeroMemory(&dsbd, sizeof(DSBUFFERDESC)); dsbd.dwSize = sizeof(DSBUFFERDESC); dsbd.dwFlags = DSBCAPS_GLOBALFOCUS | DSBCAPS_CTRLVOLUME | DSBCAPS_GETCURRENTPOSITION2; dsbd.dwBufferBytes = DS_BUFSIZE; dsbd.lpwfxFormat = &wvOut; if ( ds_lpDS->lpVtbl->CreateSoundBuffer(ds_lpDS,&dsbd, &ds_lpDSB, NULL) != DS_OK ) { return -1; } ds_hSemaphoreNotify = CreateSemaphore(NULL,DS_N,DS_N,NULL);
if( ds_hSemaphoreNotify == NULL ) return -1; return 0;
} /*
audio_play() -- 播放一塊,每解碼一幀被調(diào)用一次 返回值: 寫入到 SoundBuffer 的字節(jié)數(shù),失敗返回0 */ static int audio_play(struct audio_play *play) { LPVOID lpDSBuf; DWORD dwDSLockSize; UINT len=0; HRESULT hr; /* 1. 調(diào)用audio_pcm()解碼一幀,得到的PCM寫入到暫存區(qū)audio_pcm[] */
len = audio_pcm(pcm_data+pcm_length, play->nsamples,play->samples[0],
play->samples[1], play->mode, play->stats); pcm_length += len; if (pcm_length < DS_ONEBUF) return 0; /* 2. 若audio_pcm[]已寫滿DS_ONEBUF字節(jié),等待播放完一塊后釋放一個(gè)空閑塊 */
WaitForSingleObject(ds_hSemaphoreNotify,INFINITE);
/* 3. 將audio_pcm[]寫入到 SoundBuffer,使完成播放一塊 */
hr = ds_lpDSB->lpVtbl->Lock(ds_lpDSB,ds_dwWriteCursor,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; CopyMemory(lpDSBuf,pcm_data,dwDSLockSize); ds_lpDSB->lpVtbl->Unlock(ds_lpDSB,lpDSBuf,dwDSLockSize,NULL,0); /* 4. 更新相關(guān)變量! */
pcm_length=0;
ds_dwWriteCursor += dwDSLockSize; if( ds_dwWriteCursor >= DS_BUFSIZE) ds_dwWriteCursor -= DS_BUFSIZE; /* 5. 首次寫滿Direct SoundBuffer后,啟動定時(shí)器,開始播放 */
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, 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, WriteBytes= %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;
} 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 (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; 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; 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 = bPause;
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緩沖區(qū)ds_lpDSB中的數(shù)據(jù),DS_N-1塊 */ static void audio_flush() { int i; for( i=1; i<DS_N; i++ ) WaitForSingleObject(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_timerID = 0; } if (ds_hSemaphoreNotify != 0) { CloseHandle(ds_hSemaphoreNotify); ds_hSemaphoreNotify = 0; } if(ds_lpDS != 0) { ds_lpDS->lpVtbl->Release(ds_lpDS); ds_lpDS = 0; } ds_dwWriteCursor = 0; ds_dwPlayCursorOld = 0; ds_iWriteTimes = 0; return 0;
} int audio_dsound(union audio_control *control)
{ audio_error = 0; switch (control->command) {
case AUDIO_COMMAND_INIT: return audio_init(&control->init); case AUDIO_COMMAND_CONFIG:
return audio_config(&control->config); case AUDIO_COMMAND_PLAY:
return audio_play(&control->play); case AUDIO_COMMAND_STOP:
if (control->stop.flush) return audio_stop(); return audio_pause(1); case AUDIO_COMMAND_FINISH:
audio_flush(); return audio_close(); } return 0;
} |
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