Both AC-3 and DTS surround audio were clumsily implemented on LaserDiscs, leading to some interesting player- and disc-dependent issues. A disc that included AC-3 audio forfeited the right analog audio channel to the modulated AC-3 RF stream. If the player did not have an AC-3 output available, the next most attractive playback option would be the digital Dolby Surround or stereo audio tracks. The reason for this is the RF signal needs to bypass the audio circuitry in order to be properly processed by the demodulator. If either the player did not support digital audio tracks (common in older players), or the disc did not include digital audio tracks at all (uncommon for a disc which is mastered with an AC-3 track), the only remaining option was to fall back to a monophonic presentation of the left analog audio track. However, many older analog-only players not only failed to output AC-3 streams correctly, but were not even aware of their potential existence. Such a player will happily play the analog audio tracks verbatim, resulting in garbage (static) output in the right channel.
What happens to the right channel in a player that doesn't recognize AC-3?
garbage (static) output