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