The present invention relates to methods, a protocol, computer readable mediums and computer program products for establishing backward compatibility and forward compatibility of protocols used for communication between subsystems of an electronic trading system having different software versions. The apparatus converts an image region where same-colored data continues in a range of equal to or greater than a threshold value into solid-colored data. A first circuit determines a signal level for the audio signal and a second circuit determines an ambient sound level from a microphone signal from a microphone.