创建游戏内核（20）

本篇是创建游戏内核（19）的续篇，有关DirectAudio和DirectShow的基础知识请参阅用DirectX Audio和DirectShow播放声音和音乐。

没有了音乐，游戏将变得毫无乐趣，可以通过使用类MUSIC_CHANNEL来播放.MID和DirectMusic本地歌曲（.SGT）。

来看看类MUSIC_CHANNEL的定义:

//======================================================================================
// This class encapsulate midi file playing.
//======================================================================================
typedef class MUSIC_CHANNEL
{
    friend class SOUND;

public:
    MUSIC_CHANNEL();
    ~MUSIC_CHANNEL();

    IDirectMusicSegment8* get_dm_segment();

    BOOL create(SOUND_PTR sound);
    BOOL load(const char* filename);
    BOOL free();

    BOOL set_dls(DLS* dls);

    BOOL play(long volume_percent = 100, long loop_time = 1);
    BOOL stop();

    long get_volume();
    BOOL set_volume(long percent = 100);

    BOOL set_tempo(long percent);
    BOOL is_playing();

protected:
    SOUND_PTR               _sound;
    IDirectMusicSegment8*   _dm_segment;
    long                    _volume;
} *MUSIC_CHANNEL_PTR;

以及类MUSIC_CHANNEL的实现：

//------------------------------------------------------------------------------
// Set volume for the default audio path of DirectMusic perforfamce.
//------------------------------------------------------------------------------
BOOL set_audio_path_volume(IDirectMusicPerformance8* dm_perf, long percent)
{
    IDirectMusicAudioPath8* audio_path;
    long volume;

    if(dm_perf == NULL)
        return FALSE;

    // retrieves the default audiopath
    if(FAILED(dm_perf->GetDefaultAudioPath(&audio_path)))
        return FALSE;

    // calculate a usable volume level
    if(percent == 0)
        volume = -9600;
    else
        volume = (long) (-32.0 * (100.0 - (float)(percent % 101)));

    // set the audio volume on the audiopath, the volume can be faded in or out.
    if(FAILED(audio_path->SetVolume(volume, 0)))
    {
        audio_path->Release();
        return FALSE;
    }

    audio_path->Release();

    return TRUE;
}

//------------------------------------------------------------------------------
// Set tempo for DirectMusic performance.
//------------------------------------------------------------------------------
BOOL set_performance_tempo(IDirectMusicPerformance8* dm_perf, long percent)
{
    if(dm_perf == NULL)
        return FALSE;

    // calculate tempo setting based on percentage
    float tempo = (float) percent / 100.0f;

    // set master performance tempo
    if(FAILED(dm_perf->SetGlobalParam(GUID_PerfMasterTempo, (void*) &tempo, sizeof(float))))
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Constructor, initialize member data.
//------------------------------------------------------------------------------
MUSIC_CHANNEL::MUSIC_CHANNEL()
{
    memset(this, 0, sizeof(*this));
}

//------------------------------------------------------------------------------
// Destructor, release resource.
//------------------------------------------------------------------------------
MUSIC_CHANNEL::~MUSIC_CHANNEL()
{
    free();
}

//------------------------------------------------------------------------------
// Release DirectMusic segment and loader resource.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::free()
{
    stop();

    // unload instrument data
    if(_sound && _dm_segment)
    {
        // unloads instrument data from a performance
        if(_sound->get_dm_performance())
        {
            if(FAILED(_dm_segment->Unload(_sound->get_dm_performance())))
                return FALSE;
        }

        // releases the loader's reference to an object
        if(_sound->get_dm_loader())
        {
            if(FAILED(_sound->get_dm_loader()->ReleaseObjectByUnknown(_dm_segment)))
                return FALSE;
        }
    }

    release_com(_dm_segment);

    return TRUE;
}

//------------------------------------------------------------------------------
// Stop playing music segment.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::stop()
{
    // return if not setup correctly
    if(_sound == NULL || _sound->get_dm_performance() == NULL || _dm_segment == NULL)
        return FALSE;

    // stop palyback
    if(FAILED(_sound->get_dm_performance()->Stop(_dm_segment, NULL, 0, 0)))
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Return direct music segment.
//------------------------------------------------------------------------------
IDirectMusicSegment8* MUSIC_CHANNEL::get_dm_segment()
{
    return _dm_segment;
}

//------------------------------------------------------------------------------
// Attach SOUND object to music channel.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::create(SOUND_PTR sound)
{
    free();

    // make sure all objects there
    if((_sound = sound) == NULL)
        return FALSE;

    if(_sound->get_dm_performance() == NULL || _sound->get_dm_loader() == NULL)
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Retrieve DirestMusic segment from DirectMusic loader and download band data to
// performance.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::load(const char* filename)
{
    free();

    if(_sound == NULL)
        return FALSE;

    if(_sound->get_dm_performance() == NULL || _sound->get_dm_loader() == NULL)
        return FALSE;

    // setup DMUS_OBJECTDESC structure which used to describe a loadable object

    DMUS_OBJECTDESC obj_desc;

    ZeroMemory(&obj_desc, sizeof(DMUS_OBJECTDESC));

    obj_desc.dwSize      = sizeof(DMUS_OBJECTDESC);
    obj_desc.guidClass   = CLSID_DirectMusicSegment;
    obj_desc.dwValidData = DMUS_OBJ_CLASS | DMUS_OBJ_FILENAME | DMUS_OBJ_FULLPATH;

    mbstowcs(obj_desc.wszFileName, filename, MAX_PATH);

    // retrieves an objet from a file or resource and returns the specified interface
    if(FAILED(_sound->get_dm_loader()->GetObject(&obj_desc, IID_IDirectMusicSegment8, (LPVOID*) &_dm_segment)))
        return FALSE;

    // setup MIDI playing
    if(strstr(filename, ".mid"))
    {
        if(FAILED(_dm_segment->SetParam(GUID_StandardMIDIFile, 0xFFFFFFFF, 0, 0, NULL)))
            return FALSE;
    }

    // download band data to a performance
    if(FAILED(_dm_segment->Download(_sound->get_dm_performance())))
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Download band data from DLS.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::set_dls(DLS* dls)
{
    if(dls == NULL || dls->get_dm_colletion() == NULL)
        return FALSE;

    if(_sound == NULL || _sound->get_dm_performance() == NULL)
        return FALSE;

    if(_dm_segment == NULL)
        return FALSE;

    // sets data on a track inside this segment
    if(FAILED(_dm_segment->SetParam(GUID_ConnectToDLSCollection, 0xFFFFFFFF, 0, 0, (void*) dls->get_dm_colletion())))
        return FALSE;

    // unload and then re-download new instruments

    // unloads instrument data from a performance
    if(FAILED(_dm_segment->Unload(_sound->get_dm_performance())))
        return FALSE;

    // downloads band data to a performance
    if(FAILED(_dm_segment->Download(_sound->get_dm_performance())))
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Play music segment.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::play(long volume_percent, long loop_time)
{
    stop();

    // return if no setup coorectly
    if(_sound == NULL || _sound->get_dm_performance() == NULL || _dm_segment == NULL)
        return FALSE;

    // set the number of loops
    if(loop_time == 0)
        _dm_segment->SetRepeats(DMUS_SEG_REPEAT_INFINITE);
    else
        _dm_segment->SetRepeats(loop_time - 1);

    // set the playback volume
    set_volume(volume_percent);

    // play on default audio path
    if(FAILED(_sound->get_dm_performance()->PlaySegmentEx(_dm_segment, NULL, NULL, 0, 0, NULL, NULL, NULL)))
        return FALSE;

    return TRUE;
}

//------------------------------------------------------------------------------
// Get volume of music channel.
//------------------------------------------------------------------------------
long MUSIC_CHANNEL::get_volume()
{
    return _volume;
}

//------------------------------------------------------------------------------
// Set volume for music chanel.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::set_volume(long percent)
{
    if(_sound == NULL)
        return FALSE;

    if(! set_audio_path_volume(_sound->get_dm_performance(), percent))
        return FALSE;

    _volume = percent % 101;

    return TRUE;
}

//------------------------------------------------------------------------------
// Set tempo for DirectMusic performance.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::set_tempo(long percent)
{
    if(_sound == NULL)
        return FALSE;

    return set_performance_tempo(_sound->get_dm_performance(), percent);
}

//------------------------------------------------------------------------------
// Ascertains whether segment is playing.
//------------------------------------------------------------------------------
BOOL MUSIC_CHANNEL::is_playing()
{
    // return if not setup correctly
    if(_sound == NULL || _sound->get_dm_performance() == NULL || _dm_segment == NULL)
        return FALSE;

    // ascertains whether a specified segment or segment state is currently being heard from the speakers
    if(_sound->get_dm_performance()->IsPlaying(_dm_segment, NULL) == S_OK)
        return TRUE;

    return FALSE;
}

MUSIC_CHANNEL类同其他类的区别是： MUSIC_CHANNEL类只需要被初始化一次，初始化它使用的函数是MUSIC_CHANNEL::create。

MUSIC_CHANNEL::free函数将歌曲从内存中释放掉，以便给要加载的其他歌曲留出空间。加载歌曲时，要给MUSIC_CHANNEL::load函数提供一个音乐文件名，而且音乐还必须是.MID或DirectMusic本地歌曲（*.SGT）文件。Midi文件必须以.MID结尾，否则MUSIC_CHANNEL函数就不会采用适当的回放格式配置DirectMusic。

一旦加载了歌曲，就可以使用MUSIC_CHANNEL::play函数播放。

测试代码：

/*****************************************************************************
PURPOSE:
    Test for class MUSIC_CHANNEL.
*****************************************************************************/

#include "Core_Global.h"

class APP : public APPLICATION
{
public:
    BOOL init()
    {
        // Initialize DierctSound and DirectMusic.
        _sound.init(get_hwnd());

        // create music channel
        _music_channel.create(&_sound);

        // Retrieve DirestMusic segment from DirectMusic loader and download band data to performance.
        if(! _music_channel.load("song.mid"))
            return FALSE;

        _music_channel.set_tempo(200);

        _music_channel.play(100, 0);

        return TRUE;
    }

    BOOL frame()
    {
        return TRUE;
    }

    BOOL shutdown()
    {
        return TRUE;
    }

private:
    SOUND _sound;
    MUSIC_CHANNEL _music_channel;

};

int PASCAL WinMain(HINSTANCE inst, HINSTANCE, LPSTR cmd_line, int cmd_show)
{
    APP app;

    return app.run();
}

posted on 2007-10-09 16:44 lovedday 阅读(367) 评论(0) 编辑收藏引用

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