Originally Posted by davehancock
When you set it to HDMI the TV controls what is sent. At least with SARA software, when you set it to HDMI it will still send sound out on the optical. Many TV's dictate that the sound then be2.0 (because that is all they can handle), but some (such as my Sony A3000) will permit 5.1.
So the correct answer is "it depends".
Philosophically, the TVs aren't "dictating" what gets sent; their role in the decision is passive. The HDMI sources obtains the downstream device's (in this case, your television's) E-EDID
block, a chunk of data describing all of the device's video and audio capabilities. If the device says that it can only reproduce 2.0 or 2.1 sound, the source has to downmix 5.1 into that--it's a violation of HDMI protocol for it to send audio or video in a format that the sink cannot reproduce. That's been a problem for people who want to directly connect HDMI to their televisions, since most HDMI sources have the ability to mix only one digital sound stream, so if they mix 2.0 or 2.1 sound for an HDMI connection, that's what they have to put out on their coax or optical S/PDIF connections as well.
The IPGs for the SA DVRs (SARA and Passport at least) were modified to add an option to not output sound on HDMI at all so that they can output 5.1 on their S/PDIF connections. So, if you want to connect HDMI directly to your television and you want 5.1 sound over coax or optical S/PDIF, find and modify that setting on the DVR and connect the S/PDIF cable from it to your AVR. The only "problem" with this is that you won't be able to listen to the DVR through your television's speakers, but if you need that option, you can probably run an analog sound cable from the DVR to the television.