I want to encode my film in a 1920 x 1080 resolution and 5.1 audio to a mp4-file. I tried to use an AVC codec (H264). There you can export the audio in 5.1 (aac! no ac3) This definitely works for shorter films, but my film is 80min long and after a 12h encoding premiere CS3 crashed two times while multiplexing. I still have the encoded audio (aac) and video file (m4v) on my computer, but I did not find a program capable to multiplex these two separate streams to just one mp4- file! Any suggestions?