For an unattended installation, the command is

BrandtrackPlayer_Installer.exe /VERYSILENT /NOCANCEL /SUPPRESSMSGBOXES

Parameters

/VERYSILENT

No progress window is displayed.

/SILENT

Displays a progress window but no interaction is possible.

/NOCANCEL

Makes the installation process non-cancellable by the user.

/SUPRESSMSGBOXES

Stops most of the windows that the installer might display (except for error messages).

/LOG

Saves a file with all the information about what the installer is doing, which can be useful for diagnosing problems in more detail.

/LOG="filename"

Find more information about the commands in the official Inno Setup documentation.