I'm having a problem when playing H264 files back in Quicktime 7 on a PacPro (3GHz Quad, 5GB RAM). They look slightly sluggish and the audio appears very slightly out of sync. When played in VLC they look fine. They also play out of sync on the clients PC (what is the best codec for PC playback?). A typical file would be 1280x720, 25fps, 5000kbps, 250Mb, 48kHz audio. Source is P2.
H.264 isn't an adequate editing codec for FCP. It takes a lot of processing power to play them back, which is what you're seeing. The files should be converted to ProRes 422, using either MPEG Streamclip, Compressor, or at Log & Transfer time in FCP.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
Are you using the Quicktime H264 codec through Compressor? Are you outputting a self contained full resolution QT then bringing it into Compressor for the transcode? I personally avoid using the "Send To Compressor" setting.