We overlooked the original post and should have directed the user to Podner's FAQ answer concerning MPEG audio. VCD DAT files are MPEG-1, so their audio is muxed, or mixed into the same logical data stream, with the video. Because QuickTime cannot work with muxed audio Podner relies on a third-party tool to extract the audio, then parses the file's MPEG headers to try to gather enough information for resynchronizing the audio and video. This doesn't always work, typically because the source file is damaged or incomplete. A more complete explanation of Podner's MPEG muxed audio support is at the bottom of
http://www.splasm.com/support/faqpodner.html .
AVI files aren't subject to most of the same potential issues as MPEG, so we're moving that issue to a new thread.