Pi -> HDMI -> TV -> Optical (out) -> Bose Interface Module
From what I've been reading in the comments on Amazon, this system does not support direct DTS output and requires the signal to be stepped down.
I've been doing some testing and in Rasplex's preferences, I've checked both DTS & AC3 capable receiver. I've also added "hdmi_force_edid_audio=1" to config.txt.
This should pass the audio signal directly to the sound system, correct? In my case, I'd expect to get no sound or an unusable signal. However, the sound is coming through just fine. The video does occasionally shudder a few times during the course of a movie.
Does this mean, the Pi is in fact converting the audio signal before passing it along? Is there any way to tell? Logs?
Just wondering if you were able to get any concrete answers on this. I am seeking the same kind of info. Except I need/want the audio to pass though not transcoded and in AC3 format (7.1 surround sound with LFE). My Xbox One has two settings - 7.1 or Bitstream. I take Bitstream to be like pass though. Anyway, on my Xbox One playing video via DLNA from my PMS, the audio is louder and clearer than when playing the same video though RasPlex. Both seem to play the audio channels discretely. The Xbox One just sounds better. I was looking for a similar Bitstream setting in RasPlex and could only find what you have found as well - check mark boxes for AC3 and DTS Enabled AVR. I too am wondering if Rasplex is manipulating/transcoding.
I'm not totally clear on the specifics, but close enough. Feel free to correct me.
The problem is the optical interface from the tv. The toslink/spdif (optical) is fairly limited in its bandwith. http://en.wikipedia.org/?title=S/PDIF
"S/PDIF can carry two channels of uncompressed PCM audio or compressed 5.1/7.1 surround sound (such as DTS audio codec); it cannot support lossless formats (such as Dolby TrueHD and DTS-HD Master Audio) which require greater bandwidth like that available with HDMI or DisplayPort."
Usually this means you are stuck with stereo sound. Apps on the tv that will encode to ac3 or dts will be passed through to the receiver/soundbar compressed, and decompressed there. Netflix is one such app. This will give you multichannel sound.
The problem with sending it from the Pi to the tv and from there via optical is that the tv will uncompress the ac3/dts into all the individual channels. These can't fit through the optical, and you are stuck with stereo. You have to find a tv that will send the audio signal through untouched, but these are hard to find.
I've been looking at something like a hdmi splitter with optical audio out to get around the issue, but I'll make do with my current setup for now.
Pi -> HDMI -> TV -> Optical (out) -> Bose Interface Module
From what I've been reading in the comments on Amazon, this system does not support direct DTS output and requires the signal to be stepped down.
I've been doing some testing and in Rasplex's preferences, I've checked both DTS & AC3 capable receiver. I've also added "hdmi_force_edid_audio=1" to config.txt.
This should pass the audio signal directly to the sound system, correct? In my case, I'd expect to get no sound or an unusable signal. However, the sound is coming through just fine. The video does occasionally shudder a few times during the course of a movie.
Does this mean, the Pi is in fact converting the audio signal before passing it along? Is there any way to tell? Logs?
Rasplex is Plex HT, so the info in this document is appropriate for the Pi, except one or two of the settings are not available, but have nothing to do with your question.
Most TV's do not "passthru" 5.1 info, meaning the TV will only output 5.1 through the optical link if it's coming from its own tuner and nowhere else.
@Jenk: The TV is not allowed to pass DTS or AC3 out of the toslink due to the HDMI spec - it's a copy protection "feature". The exact same thing would happen if you replaced your pi with a bluray player - but of course a bluray player has it's own toslink output for you to use! You need an HDMI splitter. Or you could wait for the next version of PHT and Rasplex which might support the hifi-berry digi, which adds a toslink to the Pi. XMBC supports hifi-berry digi already, and there is always the PlexBMC addon.
In Matt's case (OP) it sounds like his TV supports DTS and AC3 and is downmixing to stereo and outputting that via toslink. That's exactly what my TV does.
If you do not tick the AC3 / DTS passthrough, then PHT decodes in software and downmixes to stereo.
In Matt's case (OP) it sounds like his TV supports DTS and AC3 and is downmixing to stereo and outputting that via toslink. That's exactly what my TV does.
If you do not tick the AC3 / DTS passthrough, then PHT decodes in software and downmixes to stereo.
Just to correct myself: for AC3/DTS to passthrough you must tick the boxes in audio output settings AND the pi must see AC3 and DTS in the EDID information output by tvservice -a. Contrary to what I thought, my TV does not accept AC3 or DTS via HDMI (although it does via DLNA!) and so the pi was still downmixing to 2 channels even with the boxes ticked. If your device does not set the EDID properties then adding hdmi_force_edid_audio=1 in config.txt will make DTS, AC3 and everything else appear in the output of tvservice -a. Then the pi will stop downmixing.
This doesn't work on my tv either. It's frustrating too, because when I force edid_audio, I can send AC3 to the tv and it recognises it according to the menus, but I get nothing from the optical spdif. I'll get a splitter at some point, or a new amp :)
Does anyone know if HDMI audio return channel will do any better? Can't test it since my receiver is too old, but any new one I get will obviously have support. Does anyone have any luck passing more than stereo from a hdmi input out through that?
In my experience ARC is only used by the TV to output its own audio, not audio that has come in over HDMI. I have a TV that supports ARC, works for taking my cable TV audio back to my Onkyo, but not for anything that it gets via HDMI.
In my experience ARC is only used by the TV to output its own audio, not audio that has come in over HDMI. I have a TV that supports ARC, works for taking my cable TV audio back to my Onkyo, but not for anything that it gets via HDMI.
Thats a shame. Sounds like the tv is treating it just like the optical out in that regard. I was hoping I could use the hdmi inputs on the tv for something useful, but I guess it will mostly be for random stuff like cellphones.
Does anyone know if HDMI audio return channel will do any better? Can't test it since my receiver is too old, but any new one I get will obviously have support. Does anyone have any luck passing more than stereo from a hdmi input out through that?
I use a cheap hdmi splitter and in my setup DD5.1 is passed through via ARC (DTS doesn't work). I haven't tested toslink pass through.
My setup: RPi > splitter (hdmi) > tv (arc) > splitter (toslink) > receiver
I wish the sound would travel straight from the splitter to the receiver bypassing the tv as that would probably enable DTS to work too.
