Muxing and existing .MOV file with a 5.1 AC3 file.

Hello all,
first time poster, long time visitor.

I have an existing .MOV file which has been encoded using Apple ProRes 442 (HQ), the person who encoded it added the AC3 file however the channels have not been assigned.

I want to mux the AC3 file, which has the channels on it to the .MOV file, I have tried using FCP7, FFMPEGX, StreamClip, and AVIDemux to no avail.

I have done it in Premier Pro CS6, however, The original file size was 6GB and it was 138.52 Mbit/s. However using Premier Pro CS6 to add the AC3 and using Apple ProRes 442 (HQ) to encode it made the file size 8.2GB and 175.27 Mbit/s, and the video become jittery as I beleve the video was not able to load quick enough to play.

Is there a way to mux the AC3 into the .MOV file that I have not tried, or am i not using the programs correctly.

Any help is appreciated.


PS. the title should read: Muxing an existing .MOV file with a 5.1 AC3 file.