[papalou]

The best way to output a DCP picture & sound is to have a DCP server, which is dedicated to that. With a computer-based solution, you can get issues regarding performance for decoding the JPEG2000 stream. All DCP servers or projectors (it has been deported to projectors years ago for security reasons regarding encrypted contents) have AES output, most of time on RJ45 connectors. So all you need then is a DA converter and you'll have analog audio.

If you want to do that with a computer, you should have a look to Easy DCP Player Plus, which can playout encrypted and unencrypted DCP's, and output it with a Blackmagic card. You'll need a powerful computer, there's a document about that and performance examples somewhere on their website. But it's quite pricey.

For MP4 files, both software and hardware should be able to play surround sound (not so easy to find !), most of time you'll have a small software player with video cards from Blackmagic, AJA or Matrox, but not sure it will match your needs as there's some limitations (supported codecs, sample rate, number of audio channels...). You can also do that with piece of DI softwares like Resolv or Assimilate Scratch, but it's a huge task for audio people to learn such apps IMHO.

Then you can output picture and sound to an HDMI output that can be plugged into a home cinema system or an HDMI sound extractor, or output sound separately with AES outputs (again). I still have a 888/24 here for DA conversion, when needed (with an AJA Kona card and Assimilate Scratch).

HTH !