pcm原始數據繪製

最近幫別人作了個東西，這裏分享一下pcm原始數據繪圖的思路

一、pcm數據採樣位數，根據採樣位數選取適合本身繪圖的採樣點的數量

二、計算出最大最小的的採樣點的值差

三、根據要顯示pcm數據的控件寬高，根據pcm原始數據的在pcm數據的偏移計算出x座標，根據pcm數據採樣的數值大小計算出y座標

四、繪圖，依次進行相鄰數據點繪圖

 如下是在Duilb中繪圖的代碼：

 1     std::vector<char> pcm_buffer;  2     FILE * file = NULL;  3     file = fopen("pcm\\20180601155322.pcm", "rb");  4 
 5     if (file != NULL) {  6         //  7  pcm_buffer.clear();  8  pcm_buffer.shrink_to_fit();  9 
10         fseek(file, 0, SEEK_END); 11         unsigned int size_byte = ftell(file); 12         fseek(file, 0, SEEK_SET); 13  pcm_buffer.resize(size_byte); 14         fread(&pcm_buffer[0], size_byte, 1, file); 15  fclose(file); 16         size_byte /= 2; 17         int step = 1, len = size_byte; 18         if (size_byte > 20000) { 19             len = 20000; 20             step = (int)(size_byte / len); 21  } 22         short * pcm_16 = (short*)(&pcm_buffer[0]); 23         std::vector<float> pcm_float; 24         pcm_float.resize(20000); 25         for (int i = 0, n = 0; n < len; i += step, n++) { 26             pcm_float[n] = pcm_16[i]; 27  } 28 
29         float max = pcm_float[0], min = pcm_float[0]; 30         for (int i = 1; i< pcm_float.size(); i++){ 31             if (max < pcm_float[i]){ 32                 max = pcm_float[i]; 33  } 34             if (min > pcm_float[i]){ 35                 min = pcm_float[i]; 36  } 37  } 38         int w = m_rcItem.right - m_rcItem.left; 39         int h = m_rcItem.bottom - m_rcItem.top; 40         std::vector<PointF> points; 41         float diffVal = max - min; 42         for (int i = 0; i < pcm_float.size(); i++){ 43             points.push_back(PointF(i * w / pcm_float.size(), h - (pcm_float[i] - min) / diffVal * h)); 44  } 45 
46         const DWORD backColor = 0xFFC9C9C9; 47  CRenderEngine::DrawColor(hDC, m_rcItem, backColor); 48         const DWORD backLineColor = 0xFF0000FF; 49         for (int i = 0; i < points.size() - 1; i++){ 50  RECT rect; 51             rect.left = points[i].X; 52             rect.top = points[i].Y + m_rcItem.top; 53             rect.right = points[i + 1].X; 54             rect.bottom = points[i + 1].Y + m_rcItem.top; 55             CRenderEngine::DrawLine(hDC, rect, 1, backLineColor); 56  } 57     }

 

繪圖效果:

 

測試繪圖代碼:  https://github.com/karllen/cef3-duilib-YDDemo/tree/master/PcmMediaDemo