本篇是創(chuàng)建游戲內(nèi)核（18）的續(xù)篇，有關(guān)DirectAudio和DirectShow的基礎(chǔ)知識請參閱用DirectX
Audio和DirectShow播放聲音和音樂。
使用SOUND_CHANNEL播放聲音
前面介紹了如何初始化聲音系統(tǒng)以及如何加載聲音數(shù)據(jù)，很自然地，接下來就要講述如何播放聲音了，這也正是SOUND_CHANNEL類的用途所在。
首先定義兩個全局變量來保存音頻緩沖的大小和每個音頻數(shù)據(jù)塊的大小。
// these are the fixed sizes for sound channel buffers
const long g_sound_buffer_size = 65536;
const long g_sound_buffer_chunk = g_sound_buffer_size / 4;
第一個變量g_sound_buffer_size表示分配給用于播放聲音的每個DirectSound緩沖區(qū)的字節(jié)數(shù)，這里使用65536字節(jié)，因為此大小的緩沖區(qū)足夠保存相當于數(shù)秒高品質(zhì)的聲音數(shù)據(jù)。第二個g_sound_buffer_chunk是單個聲音數(shù)據(jù)塊的大小，使用4個數(shù)據(jù)塊，每個數(shù)據(jù)塊存儲了流式聲音的一個小的采樣。每播放完一個數(shù)據(jù)塊，緊接著就
開始播放下一個數(shù)據(jù)塊，同時使用新的聲音數(shù)據(jù)加載前一個數(shù)據(jù)塊。
一般不必改變這兩個變量的值，除非想要節(jié)約內(nèi)存。如果想節(jié)約內(nèi)存，只需將g_sound_buffer_size變量的值改變成較小的數(shù)字即可。g_sound_buffer_size變量使用不同的大小，各有其優(yōu)勢，比如g_sound_buffer_size變量的值越大，聲音內(nèi)核將新數(shù)據(jù)放到流中的頻率就越小，當然這也意味著要占用更多的內(nèi)存。
來看看SOUND_CHANNEL的定義:
//======================================================================================
// This class encapsulate sound buffer playing.
//======================================================================================
class SOUND_CHANNEL
{
private:
friend class SOUND;
protected:
SOUND* _sound; // pointer to parent sound object
IDirectSoundBuffer8* _ds_buffer; // pointer to DirectSound buffer object
IDirectSoundNotify8* _ds_notify; // pointer to DirectSound notify object
short _event_index;
long _volume; // sound buffer volume
signed long _pan; // sound buffer pan
BOOL _is_playing; // sound buffer playing flag
long _loop_times; // loop times
long _frequency;
short _bits_per_sample;
short _channels;
SOUND_DATA _sound_data;
short _load_section; // sound section will to be loaded
short _stop_section; // sound section will to be stoped
short _next_notify; // sound notification index will to be played
BOOL _buffer_data();
void _update();
public:
SOUND_CHANNEL();
~SOUND_CHANNEL();
IDirectSoundBuffer8* get_sound_buffer_com();
IDirectSoundNotify8* get_notify_com();
BOOL create(SOUND* sound, long frequency = 22050, short channels = 1, short bits_per_sample = 16);
BOOL create(SOUND* sound, SOUND_DATA* sound_data);
void free();
BOOL play(SOUND_DATA* sound_data, long volume_percent = 100, long loop = 1);
void stop();
long get_volume();
BOOL set_volume(long percent);
signed long get_pan();
BOOL set_pan(signed long level);
long get_frequency();
BOOL set_frequency(long frequency);
BOOL is_playing();
};
接著來看看它的實現(xiàn)：
//------------------------------------------------------------------------------
// Constructor, initialize member data.
//------------------------------------------------------------------------------
SOUND_CHANNEL::SOUND_CHANNEL()
{
_sound = NULL;
_ds_buffer = NULL;
_ds_notify = NULL;
_event_index = -1;
_volume = 0;
_pan = 0;
_frequency = 0;
_is_playing = FALSE;
}
//------------------------------------------------------------------------------
// Destructor, release sound buffer and sound notification, set the event state
// to nonsignaled.
//------------------------------------------------------------------------------
SOUND_CHANNEL::~SOUND_CHANNEL()
{
free();
}
//------------------------------------------------------------------------------
// Return pointer to DirectSound buffer.
//------------------------------------------------------------------------------
IDirectSoundBuffer8* SOUND_CHANNEL::get_sound_buffer_com()
{
return _ds_buffer;
}
//------------------------------------------------------------------------------
// Return pointer to DirectSound notify.
//------------------------------------------------------------------------------
IDirectSoundNotify8* SOUND_CHANNEL::get_notify_com()
{
return _ds_notify;
}
//------------------------------------------------------------------------------
// Create sound buffer, set sound notification and event.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::create(SOUND* sound, long frequency, short channels, short bits_per_sample)
{
// free a prior channel
free();
if((_sound = sound) == NULL)
return FALSE;
if(_sound->get_directsound_com() == NULL)
return FALSE;
// save playback format
_frequency = frequency;
_bits_per_sample = bits_per_sample;
_channels = channels;
WAVEFORMATEX wave_format;
// create a new sound buffer for this channel, using specified format.
ZeroMemory(&wave_format, sizeof(WAVEFORMATEX));
wave_format.wFormatTag = WAVE_FORMAT_PCM;
wave_format.nChannels = (WORD) _channels;
wave_format.nSamplesPerSec = _frequency;
wave_format.wBitsPerSample = (WORD) _bits_per_sample;
wave_format.nBlockAlign = wave_format.wBitsPerSample / 8 * wave_format.nChannels;
wave_format.nAvgBytesPerSec = wave_format.nSamplesPerSec * wave_format.nBlockAlign;
DSBUFFERDESC buffer_desc;
ZeroMemory(&buffer_desc, sizeof(DSBUFFERDESC));
buffer_desc.dwSize = sizeof(DSBUFFERDESC);
buffer_desc.dwFlags = DSBCAPS_CTRLVOLUME | DSBCAPS_CTRLPAN | DSBCAPS_CTRLFREQUENCY |
DSBCAPS_CTRLPOSITIONNOTIFY | DSBCAPS_LOCSOFTWARE;
buffer_desc.dwBufferBytes = g_sound_buffer_size;
buffer_desc.lpwfxFormat = &wave_format;
IDirectSoundBuffer* ds_buffer;
if(FAILED(_sound->get_directsound_com()->CreateSoundBuffer(&buffer_desc, &ds_buffer, NULL)))
return FALSE;
// query for newer interface
if(FAILED(ds_buffer->QueryInterface(IID_IDirectSoundBuffer8, (void**) &_ds_buffer)))
{
ds_buffer->Release();
return FALSE;
}
// release old object - we have the newer one now
ds_buffer->Release();
// create the notification interface
if(FAILED(_ds_buffer->QueryInterface(IID_IDirectSoundNotify8, (void**) &_ds_notify)))
return FALSE;
HANDLE event_handle;
// get an event for this
if(! _sound->assign_event(this, &_event_index, &event_handle))
return FALSE;
DSBPOSITIONNOTIFY pos_notify[4];
// setup the 4 notification positions
pos_notify[0].dwOffset = g_sound_buffer_chunk - 1;
pos_notify[0].hEventNotify = event_handle;
pos_notify[1].dwOffset = g_sound_buffer_chunk * 2 - 1;
pos_notify[1].hEventNotify = event_handle;
pos_notify[2].dwOffset = g_sound_buffer_chunk * 3 - 1;
pos_notify[2].hEventNotify = event_handle;
pos_notify[3].dwOffset = g_sound_buffer_size - 1;
pos_notify[3].hEventNotify = event_handle;
if(FAILED(_ds_notify->SetNotificationPositions(4, pos_notify)))
return FALSE;
// set the pan and default volume
set_volume(100);
set_pan(0);
return TRUE;
}
//------------------------------------------------------------------------------
// Create sound buffer.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::create(SOUND* sound, SOUND_DATA* sound_data)
{
return create(sound, sound_data->_frequency, sound_data->_channels, sound_data->_bits_per_sample);
}
//------------------------------------------------------------------------------
// Release sound buffer and sound notification, set the event state to nonsignaled.
//------------------------------------------------------------------------------
void SOUND_CHANNEL::free()
{
// stop any playback
stop();
// release the notification
release_com(_ds_notify);
// release the sound buffer
release_com(_ds_buffer);
// release event from parent SOUND class
_sound->release_event(this, &_event_index);
// set to no parent sound
_sound = NULL;
}
//------------------------------------------------------------------------------
// Play sound buffer.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::play(SOUND_DATA* sound_data, long volume_percent, long loop_times)
{
if(sound_data == NULL || _ds_buffer == NULL || _ds_notify == NULL)
return FALSE;
// stop any playback
stop();
// restore a lost buffer just in case
_ds_buffer->Restore();
// setup playing information
_sound_data.copy(sound_data);
// set looping times
_loop_times = loop_times;
// calculate stop section position
if(_loop_times == 0)
_stop_section = -1;
else
_stop_section = (short)
(((_sound_data._buffer_size * _loop_times) % g_sound_buffer_size) / g_sound_buffer_chunk) ;
_load_section = 0;
// load sound data into sound buffer from sound file or sound data object
_buffer_data();
_buffer_data();
_buffer_data();
_buffer_data();
// set the volume
set_volume(volume_percent);
// set position and begin play
_next_notify = 0;
if(FAILED(_ds_buffer->SetCurrentPosition(0)))
return FALSE;
if(FAILED(_ds_buffer->Play(0, 0, DSBPLAY_LOOPING)))
return FALSE;
// flag as playing
_is_playing = TRUE;
return TRUE;
}
//------------------------------------------------------------------------------
// Stop playing DirectSound buffer.
//------------------------------------------------------------------------------
void SOUND_CHANNEL::stop()
{
if(_ds_buffer)
_ds_buffer->Stop();
_is_playing = FALSE;
}
//------------------------------------------------------------------------------
// Get sound buffer volume.
//------------------------------------------------------------------------------
long SOUND_CHANNEL::get_volume()
{
return _volume;
}
//------------------------------------------------------------------------------
// Set volume for sound buffer.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::set_volume(long percent)
{
long volume;
if(_ds_buffer == NULL)
return FALSE;
// calculate a usable volume level
if(percent == 0)
volume = DSBVOLUME_MIN;
else
volume = -20 * (100 - (percent % 101));
if(FAILED(_ds_buffer->SetVolume(volume)))
return FALSE;
_volume = percent % 101;
return TRUE;
}
//------------------------------------------------------------------------------
// Get sound buffer pan.
//------------------------------------------------------------------------------
signed long SOUND_CHANNEL::get_pan()
{
return _pan;
}
//------------------------------------------------------------------------------
// Set pan for sound buffer.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::set_pan(long level)
{
signed long pan;
if(_ds_buffer == NULL)
return FALSE;
// calculate a suable setting
if(level < 0)
pan = DSBPAN_LEFT / 100 * (-level % 101);
else
pan = DSBPAN_LEFT / 100 * (level % 101);
if(FAILED(_ds_buffer->SetPan(pan)))
return FALSE;
_pan = level % 101;
return TRUE;
}
//------------------------------------------------------------------------------
// Get sound buffer frequency.
//------------------------------------------------------------------------------
long SOUND_CHANNEL::get_frequency()
{
return _frequency;
}
//------------------------------------------------------------------------------
// Set frequency for sound buffer.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::set_frequency(long frequency)
{
if(_ds_buffer == NULL)
return FALSE;
if(FAILED(_ds_buffer->SetFrequency(frequency)))
return FALSE;
_frequency = frequency;
return TRUE;
}
//------------------------------------------------------------------------------
// Checks whether sound buffer is playing.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::is_playing()
{
if(_sound == NULL || _ds_buffer == NULL || _ds_notify == NULL)
return FALSE;
return _is_playing;
}
//------------------------------------------------------------------------------
// Load sound data into sound buffer from sound file or sound data object.
//------------------------------------------------------------------------------
BOOL SOUND_CHANNEL::_buffer_data()
{
if(_ds_buffer == NULL)
return FALSE;
// setup position to load in
long lock_pos = (_load_section % 4) * g_sound_buffer_chunk;
long size;
char* ptr;
// lock sound buffer to get pointer to sound data
if(FAILED(_ds_buffer->Lock(lock_pos, g_sound_buffer_chunk, (void**) &ptr, (DWORD*)&size, NULL, NULL, 0)))
return FALSE;
// clear out buffer if nothing left to load
if(_sound_data._left_size == 0)
ZeroMemory(ptr, size);
else
{
// load in the data - take looping into account
long load_size = size;
long load_pos = 0;
// load sound data until specfied load size is satisfied
for(;;)
{
if(_sound_data._left_size > load_size)
{
// load in sound data
if(_sound_data._fp != NULL)
{
// load in sound data from file
fseek(_sound_data._fp, _sound_data._file_curr_pos, SEEK_SET);
fread(&ptr[load_pos], 1, load_size, _sound_data._fp);
}
else
// load into sound data from buffer
memcpy(&ptr[load_pos], &_sound_data._ptr[_sound_data._file_curr_pos], load_size);
// decrease sound data, advance current sound buffer position.
_sound_data._left_size -= load_size;
_sound_data._file_curr_pos += load_size;
break;
}
else // _sound_data._left_size <= load_size
{
// load in sound data
if(_sound_data._fp != NULL)
{
// load in sound data from file
fseek(_sound_data._fp, _sound_data._file_curr_pos, SEEK_SET);
fread(&ptr[load_pos], 1, _sound_data._left_size, _sound_data._fp);
}
else
// load in sound data from buffer
memcpy(&ptr[load_pos], &_sound_data._ptr[_sound_data._file_curr_pos], _sound_data._left_size);
// decrease sound data, advance current sound buffer position.
load_size -= _sound_data._left_size;
load_pos += _sound_data._left_size;
// check if we need to stop loop
if(_loop_times >= 1)
{
_loop_times--;
if(_loop_times == 0)
{
// clear out remaining buffer space
if(load_size)
ZeroMemory(&ptr[load_pos], load_size);
_sound_data._left_size = 0L;
break;
}
}
// reset sound data current position and left size
_sound_data._file_curr_pos = _sound_data._file_start_pos;
_sound_data._left_size = _sound_data._buffer_size;
// set if we need to stop loading data
if(load_size == 0)
break;
}
}
}
// unlock the buffer
_ds_buffer->Unlock(ptr, size, NULL, 0);
// mark next section to load
if(++_load_section > 3)
_load_section = 0;
return TRUE;
}
//------------------------------------------------------------------------------
// Update for sound buffer palying.
//------------------------------------------------------------------------------
void SOUND_CHANNEL::_update()
{
// check for end of sound
if(_next_notify == _stop_section && _sound_data._left_size == 0)
stop();
else
{
// buffer in more data
_buffer_data();
if(++_next_notify > 3)
_next_notify = 0;
}
}
最多可以將SOUND_CHANNEL類實例化32次，也就是說同時可以用多達32個聲道進行播放（聲音內(nèi)核不允許同時32個以上的實例，任何超過32的值，都無法被成功初始化）。調(diào)用SOUND_CHANNEL::create函數(shù)可以初始化各個聲道，需要提供一個預初始化的SOUND類以及回放格式。為方便起見，甚至可以使用存儲在SOUND_DATA類中的回放格式創(chuàng)建聲道。
使用SOUND_CHANNEL類進行的操作中，最頻繁的就是播放聲音、停止播放聲音以及改變聲音的音量。要播放聲音，需要給SOUND_CHANNEL::play函數(shù)傳遞三個參數(shù)：保存在SOUND_DATA類中要播放的聲音數(shù)據(jù)、音量的大小以及連續(xù)播放聲音的次數(shù)。
接著我們編寫測試代碼：
點擊下載源碼和工程
/*****************************************************************************
PURPOSE:
Test for class SOUND, SOUND_DATA, SOUND_CHANNEL.
*****************************************************************************/
#include "Core_Global.h"
class APP : public APPLICATION
{
private:
SOUND _sound;
SOUND_DATA _sound_data[2];
SOUND_CHANNEL _sound_channel[2];
FILE* _fp;
public:
APP()
{
_fp = NULL;
}
BOOL init();
BOOL frame();
BOOL shutdown();
};
BOOL APP::init()
{
// Initialize DierctSound and DirectMusic.
_sound.init(get_hwnd());
// load into sound data from wave file
_sound_data[0].load_wav("test1.wav", NULL);
_sound_data[1].load_wav("test2.wav", NULL);
// create sound channel
_sound_channel[0].create(&_sound, &_sound_data[0]);
_sound_channel[1].create(&_sound, &_sound_data[1]);
// play sound
_sound_channel[0].play(&_sound_data[0]);
_sound_channel[1].play(&_sound_data[1], 100, 0); // lopping forever
return TRUE;
}
BOOL APP::frame()
{
return TRUE;
}
BOOL APP::shutdown()
{
if(_fp)
fclose(_fp);
return TRUE;
}
int PASCAL WinMain(HINSTANCE inst, HINSTANCE, LPSTR cmd_line, int cmd_show)
{
APP app;
return app.run();
}