fix compile error in linux

@@ -102,21 +102,21 @@ void get_video_first_frame_jpeg(fileinfo video, char * destfile)
 	run_shell_cmd(buf);
 }
 
-void merge_audio_pic(fileinfo audio, int nf, fileinfo video, char * destfile)
+void merge_audio_pic(fileinfo audio, int nf, fileinfo video, const char * destfile)
 {
 	char buf[2048];
 	sprintf(buf, "ffmpeg -y -loop 1 -i %s.jpg -i %d_%s -loop 0 -shortest %s %s %s", video.name.c_str(), nf, audio.name.c_str(),acodec_param, vcodec_param, destfile);
 	run_shell_cmd(buf);
 }
 
-void megre_audio_video(fileinfo audio, int nf, fileinfo video, char * destfile)
+void megre_audio_video(fileinfo audio, int nf, fileinfo video, const char * destfile)
 {
 	char buf[2048];
 	sprintf(buf, "ffmpeg -y -i %d_%s -i %s %s %s %s", nf, audio.name.c_str(), video.name.c_str(), acodec_param, vcodec_param, destfile);
 	run_shell_cmd(buf);
 }
 
-void concate_files(vector<string > merged_files, char * destfile)
+void concate_files(vector<string > merged_files, const char * destfile)
 {
 	char buf[2048];
 #ifdef WIN32
@@ -140,21 +140,29 @@ void concate_files(vector<string > merged_files, char * destfile)
 	run_shell_cmd(buf);
 }
 
-void adjust_dest_timecode(char * src , char * dest)
+void adjust_dest_timecode(const char * src , const char * dest)
 {
 	char buf[2048];
 	sprintf(buf, "ffmpeg -y -i %s -acodec copy -vcodec copy %s", src, dest);
 	run_shell_cmd(buf);
 }
 
+#ifndef WIN32
+#include <unistd.h>
+#endif
+
 void removefiles(vector<string> files)
 {
 	for (int i = 0; i < files.size(); i++) {
+#ifdef WIN32
 		_unlink(files[i].c_str());
+#else
+		unlink(files[i].c_str());
+#endif
 	}
 }
 
-int process_files(char * output_dest_file)
+int process_files(const char * output_dest_file)
 {
 	vector<fileinfo>  & filesaudio = media_files[type_audio];
 	vector<fileinfo>  & filesvideo = media_files[type_video];