I have an m2ts video that has two AC-3 (5.1 ch) audio tracks. I want to convert it to an mp4 file to play on my ATV3. I want the mp4 file to have the versatility of playing audio through either a receiver or the TV, but not both at the same time because only one TV in the house has a receiver surround system that it is hooked up to and I have an ATV connected to another TV without a receiver. I would like to preserve the original ac-3 audio (5.1 ch) quality to play through my Yamaha receiver so that's why I am selecting AC-3 passthru for one of my audio tracks in Handbrake. When I encode only one audio track with AAC, I can hear audio on my TV. When I add a second audio track and select AC-3 passthru, I can hear sound on the speakers through my receiver only, which happens to be great dolby digital surround sound, but I cannot hear sound on my tv. I changed the order of the audio tracks which made no difference. (eg. audio track 1 aac, and track 2 ac-3, and vice versa). Additionally, I downloaded the movie Frozen which is an mp4 file and did not touch it with Handbrake. The sound plays through my TV as well as my receiver. I checked the file with MediaInfo and there are 3 audio tracks: Audio#1 is AAC 2 channel, Audio #2 is AC-3 (5.1 ch), and Audio#3 is AAC (7.1 ch). There must me something I am doing in Handbrake because why would Frozen play sound through my TV? I have checked other forums and I thought the reason for adding more than one audio track is so the file can play sound on different devices. I also thought that if there is both AC-3 and AAC, then ATV will detect the aac and decode it. This is very frustrating. Thank you for your help in advance.