Hello, this is my first post. I downloaded several quad recordings which are in 4-channel flac, dvd-a and mkv, if I play them through VLC will only the front channels play? Is there a way to convert them to two-channel sq/rm encoded files so I can play them from my computer to my quad receiver, or do i have to get a 4 channel sound card and play in discrete?
The device that connects to your computer's firewire, USB, or thunderbolt port and has audio inputs and outputs is called an audio interface. Think of an HDMI surround receiver as an audio interface, preamp unit, and amplifiers in the same box. If you have just a 'vintage' receiver (ie preamp and amps) version of that, you need a separate audio interface.
These are two lower budget (but professional and higher quality than most consumer electronics) examples that have at least 4 or 6 output channels:
Focusrite Scarlett 6i6 $260 new $150 used
Presonus Audiobox 44vsl $200 new $120 used *** This one only has 4 analog outputs! Would do quad for you though.
Moving into the "If you have to ask..." territory:
Apogee Element 46 $900 new (6 analog outputs)
Looks like you can get an Apogee Rosetta 800 (8 analog outputs, 8 analog inputs + some digital I/O) for $500 used. That's a pretty sweet price for this level of DA and AD converters. This thing went for over $2000 new!
Not even going to look at Prism right now...
That B-word product mentioned above... It's not just going to sound bad. Behringer's issue is ratty cheapness. Something will break quickly.
The HDMI interface mentioned... Boy that looks cheap! Just little 1/8" unbalanced connections for the audio? Any shenanigans going on with the HDMI connections? There's opportunity for copy protection gone wild here. Feeding an HDMI input on something from a thunderbolt port is one thing but all HDMI on both ends is asking for frustration.
The modern thunderbolt to HDMI connection to a surround receiver is slick. As long as you have a newer than 2010 computer, an HDMI surround receiver, and you didn't fall for some of the scammy products with HDMI inputs with audio disabled and the like.
A separate audio interface always works. You could go back to a circa 2000 computer and plug in a USB or firewire model and it will just work. (Or get one of the new generation of budget computers with circa 2000 specs and only a USB port!)