av_log_default_callback(ptr, level, fmt, vl);
av_log_format_line(ptr, level, fmt, vl2, line, sizeof(line), &print_prefix);
va_end(vl2);
av_log_default_callback(ptr, level, fmt, vl);
av_log_format_line(ptr, level, fmt, vl2, line, sizeof(line), &print_prefix);
va_end(vl2);