Cocos2d-x项目移植到WP8系列之五：播放MP3

原文链接： http://www.cnblogs.com/zouzf/p/3972549.html

这一块的细节还是不太了解，只是东凑西拼能跑起来而已

1、网上下载lamb库 生成需要的lib库，详情见 【Advanced Windows Phone Programming】在windows phone 8中录制MP3和AAC及Amr音频  第三点的前半部分，也就是生成lib那一部分，然后在CocosDenshion工程里引用那两个lib。

2、把CocosDenshion工程里的Audio.cpp里的void Audio::PreloadSoundEffect(const char* pszFilePath, bool isMusic) 方法里的m_soundEffects[sound].m_soundID = sound; 这句代码之前的代码改成如下：

     if (m_engineExperiencedCriticalError) {
         return;
     }

     std::string path(pszFilePath);

     int sound = Hash(pszFilePath);

     MediaStreamer mediaStreamer;

     // no MP3 support for CC_PLATFORM_WP8
     std::string::size_type pos = path.find(".mp3");
     if (pos  != path.npos)
     {
         //path.replace(pos, path.length(), ".wav");

         mediaStreamer.Initialize_MP3(CCUtf8ToUnicode(pszFilePath).c_str());
     }
     else
     {
         mediaStreamer.Initialize(CCUtf8ToUnicode(pszFilePath).c_str());
     }

 //    mediaStreamer.Initialize(CCUtf8ToUnicode(pszFilePath).c_str());
     m_soundEffects[sound].m_soundID = sound;    

3、CocosDenshion工程里的MediaStreamer类加多一个方法：void MediaStreamer::Initialize_MP3(__in const WCHAR* url)，实现如下：

 void MediaStreamer::Initialize_MP3(__in const WCHAR* url)
 {

     WCHAR filePath[MAX_PATH] = {};
     if ((wcslen(url) >  && url[] == ':'))
     {
         // path start with "x:", is absolute path
         wcscat_s(filePath, url);
     }
     else if (wcslen(url) >
         && (L'/' == url[] || L'\\' == url[]))
     {
         // path start with '/' or '\', is absolute path without driver name
         wcscat_s(filePath, m_locationPath->Data());
         // remove '/' or '\\'
         wcscat_s(filePath, (const WCHAR*)url[]);
     }else
     {
         wcscat_s(filePath, m_locationPath->Data());
         wcscat_s(filePath, url);
     }

     hip_t hip = hip_decode_init();
     if (!hip)
     {
         printf("创建mp3解码失败");
         return ;
     } 

     mp3data_struct mp3str;//mp3文件编码信息
     std::vector<short*> mp3Buffer;// mp3数据流
     std::vector<int> mp3BufferSize;

     int samples;
     int mp3_bytes;
     int write_bytes = ;

     const int BUF_SIZE = ;
     const int INBUF_SIZE = ;
     const int MP3BUF_SIZE = (int)(1.25 * BUF_SIZE) + ;

     short pcm_l[INBUF_SIZE];
     short pcm_r[INBUF_SIZE];
     unsigned char mp3_buf[MP3BUF_SIZE];

     FILE * MP3File;

     std::wstring wstr = std::wstring(filePath);
 //    return std::string(wstr.begin(),wstr.end());

     std::string str_filePath = std::string(wstr.begin(),wstr.end());//"C:\\Data\\Programs\\{4AE99D96-62EE-4A1C-A345-F1B0A81D07BC}\\Install\\Assets\\Resources\\islandbg.mp3";

     auto error = fopen_s(&MP3File, str_filePath.c_str(), "rb");
     mp3data_struct mp3Header;

     while ((mp3_bytes = fread(mp3_buf, , , MP3File)) > )
     {
         samples = hip_decode_headers(hip, mp3_buf, , pcm_l, pcm_r, &mp3Header);
         if (samples > )
         {
             short *tt = new short[samples*sizeof(short)];
             memcpy((void*)tt, (const void*)pcm_l, samples*sizeof(short));
             mp3Buffer.push_back(tt);
             write_bytes += samples*sizeof(short);
             mp3BufferSize.push_back(samples*sizeof(short));
             //write_bytes = fwrite(pcm_l, sizeof(short), samples, wavfp);
         }
     }

     byte* _mp3Buffer = new byte[write_bytes];
     byte* temp = _mp3Buffer;
     int size = mp3BufferSize.size();
     for(int i=;i<size;i++)
     {
         memcpy(temp, mp3Buffer[i],mp3BufferSize[i]);
         delete mp3Buffer[i];
         temp += mp3BufferSize[i];
     }
     mp3Buffer.clear();
     hip_decode_exit(hip);
     //m_soundEffects[sound].m_soundEffectBufferData

     m_data.resize(write_bytes);
     for(int i=;i<write_bytes;i++)
     {
         m_data[i]=_mp3Buffer[i];
     }

     fclose(MP3File);

     m_waveFormat.wFormatTag = WAVE_FORMAT_PCM; //固定
     m_waveFormat.nChannels = ; //固定
     m_waveFormat.nSamplesPerSec = (DWORD) mp3Header.samplerate;// 固定 

     m_waveFormat.wBitsPerSample = ;// mp3Header.bitrate * m_waveFormat.nChannels / 8;
     //m_waveFormat.wBitsPerSample = mp3Header.bitrate * m_waveFormat.nChannels / 8.0;
     m_waveFormat.nBlockAlign = m_waveFormat.nChannels * m_waveFormat.wBitsPerSample / 8.0;
     m_waveFormat.nAvgBytesPerSec = m_waveFormat.nSamplesPerSec * m_waveFormat.nBlockAlign; //越大越快
     m_waveFormat.cbSize = ;

 }

完成。

大概流程就是，通过lamb的两个lib库的方法，读取MP3文件的流构建成wav文件格式的流，重点在于通过MP3的文件头信息mp3data_struct 构建出 wav文件的文件头信息WAVEFORMATEX。

另外，因为只读取了一个声道的流，所以m_waveFormat.nChannels = 1;如果对声道有要求的，可以在while循环里把右声道的流也处理一下。

附上一些参考文章： lame mp3解码   Suche MP3 to WAV decoder

原文链接： http://www.cnblogs.com/zouzf/p/3972549.html