pcm原始数据绘制

最近帮别人做了个东西，这里分享一下pcm原始数据绘图的思路

1、pcm数据采样位数，根据采样位数选取适合自己绘图的采样点的数量

2、计算出最大最小的的采样点的值差

3、根据要显示pcm数据的控件宽高，根据pcm原始数据的在pcm数据的偏移计算出x坐标，根据pcm数据采样的数值大小计算出y坐标

4、绘图，依次进行相邻数据点绘图

以下是在Duilb中绘图的代码：

     std::vector<char> pcm_buffer;
     FILE * file = NULL;
     file = fopen("pcm\\20180601155322.pcm", "rb");

     if (file != NULL) {
         //
         pcm_buffer.clear();
         pcm_buffer.shrink_to_fit();

         fseek(file, , SEEK_END);
         unsigned int size_byte = ftell(file);
         fseek(file, , SEEK_SET);
         pcm_buffer.resize(size_byte);
         fread(&pcm_buffer[], size_byte, , file);
         fclose(file);
         size_byte /= ;
         int step = , len = size_byte;
         if (size_byte > ) {
             len = ;
             step = (int)(size_byte / len);
         }
         short * pcm_16 = (short*)(&pcm_buffer[]);
         std::vector<float> pcm_float;
         pcm_float.resize();
         for (int i = , n = ; n < len; i += step, n++) {
             pcm_float[n] = pcm_16[i];
         }

         float max = pcm_float[], min = pcm_float[];
         for (int i = ; i< pcm_float.size(); i++){
             if (max < pcm_float[i]){
                 max = pcm_float[i];
             }
             if (min > pcm_float[i]){
                 min = pcm_float[i];
             }
         }
         int w = m_rcItem.right - m_rcItem.left;
         int h = m_rcItem.bottom - m_rcItem.top;
         std::vector<PointF> points;
         float diffVal = max - min;
         for (int i = ; i < pcm_float.size(); i++){
             points.push_back(PointF(i * w / pcm_float.size(), h - (pcm_float[i] - min) / diffVal * h));
         }

         const DWORD backColor = 0xFFC9C9C9;
         CRenderEngine::DrawColor(hDC, m_rcItem, backColor);
         const DWORD backLineColor = 0xFF0000FF;
         for (int i = ; i < points.size() - ; i++){
             RECT rect;
             rect.left = points[i].X;
             rect.top = points[i].Y + m_rcItem.top;
             rect.right = points[i + ].X;
             rect.bottom = points[i + ].Y + m_rcItem.top;
             CRenderEngine::DrawLine(hDC, rect, , backLineColor);
         }
     }

绘图效果:

测试绘图代码: https://github.com/karllen/cef3-duilib-YDDemo/tree/master/PcmMediaDemo