VLC 的 `:sout` 轉碼輸出鏈實現同時預覽與存文件。
string param = ":sout=#transcode{vcodec=h264,vb=800,acodec=mpga,ab=128,channels=2,samplerate=44100}" +
":file{dst=D:\\rec.mp4,overwrite} :sout-all :sout-keep";
axVLCPlugin21.playlist.clear();
axVLCPlugin21.playlist.add("rtsp://192.168.1.168:554/stream", null, param);
axVLCPlugin21.playlist.play();