server : ffmpeg overwrite leftover temp file (#2431)

* Remove possible leftover ffmpeg temp file from a previous failed conversion

* Revert "Remove possible leftover ffmpeg temp file from a previous failed conversion"

This reverts commit 0079740.

* Flag to force ffmpeg to overwrite output file if it exists

examples/server/server.cpp

@@ -219,7 +219,7 @@ void check_ffmpeg_availibility() {
 bool convert_to_wav(const std::string & temp_filename, std::string & error_resp) {
     std::ostringstream cmd_stream;
     std::string converted_filename_temp = temp_filename + "_temp.wav";
-    cmd_stream << "ffmpeg -i \"" << temp_filename << "\" -ar 16000 -ac 1 -c:a pcm_s16le \"" << converted_filename_temp << "\" 2>&1";
+    cmd_stream << "ffmpeg -i \"" << temp_filename << "\" -y -ar 16000 -ac 1 -c:a pcm_s16le \"" << converted_filename_temp << "\" 2>&1";
     std::string cmd = cmd_stream.str();
 
     int status = std::system(cmd.c_str());