Question about audio when transcoding - does it remain 5.1?

[ubnewbie2]

I have a mythtv system with 2 DVB-T tv cards.

I am setting up transcoding for the first time, and I am transcoding the video to mpeg4. On the transcoding settings page for audio, I can choose mp3 or uncompressed. There is nothing mentioned there about how it handles the audio if it is dolby or dts 5.1 channel.

I am hoping that the uncompressed setting, just leaves the audio as it is in the original recording. Does it?

Also, if I choose mp3, does it retain the 5.1 channels if they exist?

[ubnewbie2]

I have done a lot of searching, and it seems that any transcode, even "uncompressed" audio, gets mixed down to stereo. Surely this is going to start becoming a limitation as more program material is transmitted in 5.1? Even a mix down to Dolby ProLogic would be better than stereo, but why not retain the AC3 5.1 channels?