AVOutputFormat *ofmt; ofmt = guess_format("audio_device", NULL, NULL); if (!ofmt) {
file_iformat = NULL; file_oformat = guess_format("audio_device", NULL, NULL); if (!file_oformat) {
void prepare_play(void){    AVOutputFormat *ofmt;    ofmt = guess_format("audio_device", NULL, NULL);    if (!ofmt) {        fprintf(stderr, "Could not find audio device\n");        exit(1);    }        opt_output_file(audio_device);}