S/PDIF Problems...New to the interface

[bleedink]

Hey all. You might recall a couple weeks ago I posted something about an article on HDMI from Cnet which asserted that the interface was akin to the balanced outputs from XLR...of course this was thoroughly debunked by the astute members of this forum. It also provided some of the most concrete reasons I have found for not using it for audio. So I switched to a basic s/pdif connection from my Oppo to my receiver. So far, so good. SQ was absolutely bested. I am sure some kind of asynchronous tech in between would serve me even better, but it was an incremental improvement. Not on the order of magnitude I got from speakers and a better amp, but good nonetheless. My problems come in when I am streaming to the Oppo. Seems the only way I can get anything in PCM 5.1 out of my receiver is using HDMI. All my flac and wavs that aren't encoded with some kind of DTS signal that the two can lock onto, I get 2 channel audio. DTS passes thru just fine, sounds brilliant, ect. But when I get to the DVD-A's I've ripped into multichannel flac or wavs as PCM audio, or when I play the discs themselves out the s/pdif I get stereo. Go back to HDMI, I get 4, 5, or 5.1 channels. I guess I am a bit confused as to why I've run against this wall. There are two settings on the Oppo and I am not sure if this is something to do with the situation or not. The Oppo gives me the option to bitstream audio out either hdmi or spdif. It also gives me a LPCM option. I've chosen the former as I have heard (perhaps incorrectly) that bitstreaming is preferable to LPCM conversion(?)--though in this case I am not at all certain there's any conversion that needs to happen between PCM and LPCM as I sorta assumed they were the same thing. I am not even sure it matters. Anyway if some audio wizard might be able to offer some advice here on how to get my discs and rips to play in their native multichannel glory I'd be very happy. So far I have only been able to get DTS as I said. I am guessing perhaps this is why no external DACs do multichannel? Some limitation of the implementation of s/pdif? I thought for some reason Oppo had found a way around this but when I went to play an SACD over s/pdif my receiver wouldn't decode it as it normally does over HDMI. I suspect there are a few topics here that I am not certain how to differentiate for the purposes of this site. If that is the case please forgive me. For some reason I guess I just thought s/pdif was pretty much capable of multichannel stuff so I am a bit baffled why I can't get it working, or is it that it is only capable of pass-through? If that was the case it would seem DSD would 'pass-through' just fine a la HDMI, right? Wrong, most likely I am sure! Can somebody help me out or point me to the right place?

PS I should add I am streaming from JRiver running on Parallels on a boot camp partition on my mac. Windows, Jriver, and Parallel all seem to agree that they are 5.1 capable and Jriver is set to Wasapi and leave all as source. Just an FYI as I have noticed Jriver will only output what it streams as a function of the audio equipment on the windows machine and its configuration. If windows is set to stereo Jriver will stream stereo...at least this has been my experience though I dont understand it.

 

[Audio_ELF]

First off, to get high resolution multi-channel you will always need to use HDMI. Once you have HDMI link, there are two methods of transferring the "audio" to your AV system - bitstream or LPCM. With bitstream the data is sent as encoded (DTS or Dolby Digital) information which the AV receiver has to decode. Alternatively you can get the Bluray player to decode this information and send it as LPCM (decodes, stream of digital sound). There is a lot of arguments over the best method of transferring multi-channel audio - most people prefer bitstream but thats mostly because people like the "DTS HD Master Audio" lights to show on their AV receiver. A few companies such as Meridian refuse to embrace bitstreaming of multi-channel audio.

 

Now with your SPDIF connection, the best that can achieve is multi-channel compressed bitstream or stereo LPCM. If you select the SPDIF output to bitstream it's likely any multi-channel audio is re-encoded as DTS. With a stereo signal the output will be sent as PCM. High resolution (DVD-A and SACD) is also usually not permitted from the SPDIF output of a player.

 

Basically (and IMO) for multi-channel a HDMI link is preferable but for stereo then a SPDIF is preferable. I'm unsure if the Oppo can be used this way...

 

Hope this description helps and doesn't confuse you.

 

Eloise

 

[bleedink]

That pretty much cleared it up for me. I absolutely prefer the spdif for stereo. I mainly needed to know it was a limitation of the connect rather than a configuration issue. Your reply was very much appreciated. The encoded music sounds fab at least. Many thanks Eloise!

 

[soundsolutions11]

"There is a lot of arguments over the best method of transferring multi-channel audio - most people prefer bitstream but that's mostly because people like the "DTS HD Master Audio" lights to show on their AV receiver."

 

I understood that the reason one output is selected over the other is primarily based upon which device has the better decoder, for example I have my PS3 set to bitstream so that my Krell HTS 7.1 does all of the decoding, which is way better than using the decoders in the PS3, hence the better sound. I use Toslink out of the PS3 and it gives me multi channel audio in either DTS or Dolby 5.1 depending upon the source file.

 

[Audio_ELF]

With your Krell, as far as I know you are not able to use HDMI (for audio). The issues here are different and you only option (for multiple-channel) is bitstream via TOSLink.

 

Eloise

 

[bleedink]

Eloise is correct. I am getting multi from encoded files, my issue again involves multi PCM playback over spdif. Though I do understand what you are saying. Im not certain my oppo would do any better at the decode than my receiver, though I may be wrong--the yamaha I have isn't at all bad for music tho it is an HT technically. It has a separate dac/each channel so I doubt the oppo could compete.

 

[soundsolutions11]

I have read that the Oppo has pretty darn good specs for decoding. I would say that it could very well be better than the Yamaha. Elosie is right about my Krell not having HDMI but he did not address the point about which device should really be doing the decoding for the best sound quality.

 

[bleedink]

so what is the proper setting to get the oppo to do the decoding? Is that the LPCM thing?

 

[soundsolutions11]

I believe that you would want to set it to LPCM. You could always try it and do a comparison, but the Oppo is a great product especially for the price!

 

[Audio_ELF]

IF using HDMI then the results should be identical whatever device is doing the decoding. However there may be variations (Meridian use £150 Sony bluray player to demo £100,000 audio setup)

 

IF using SPDIF then you have no choice but to decode in the processor.

 

Eloise

 

[PeterSt]

Not sure if this is going to help, and not even sure about the being 100% correct of what I'm saying - but I'll try anyway.

 

First off, from various posts floating around in here, to me it seems that JR depends on the resampler from Windows. IOW, it won't allow Exclusive Mode WASAPI - and thus uses Shared Mode. In that case you'd indeed be dependend on the Windows setting concerned. Otherwise (Exclusive Mode) Windows doesn't interfere with it at all (I am using multi channel myself (XXHighEnd) for WASAPI as well as Kernel Streaming -> don't try it, because it's not the multi channel like 6 channel audio, but technically it's 100% the same).

 

Next (but this has been said already I think), Encoded DTS can be streamed over SPDIF.

 

More importantly, decoded DTS can be streamed over SPDIF just the same, but it is here where I must guess a little bit on to what extension this really works or stops working;

All I know is that I use software decoding for it (this is fairly rare in AV land, but I do it), and that the output stream goes over firewire to the several output channels in the soundcard. In my case this is a Fireface800 (a FF400 sure would work the same), and the trick is to have a setting in the soundcard that allows the synching of the channels. So, a soundcard can be as multi channel as it wants, without this sync option it won't go. BUT ...

 

But the vague part (for me) is introduced at the outputs of the soundcard, because in this situation - where SPDIF is actually physically used (!!), you won't be outputting more than two channels over SPDIF. Think of this schematic :

 

Multichannel File -> In-PC decoding -> send to soundcard over FireWire -> **output to external DAC's over SPDIF** -> output to amps + speakers.

 

The ** bit is the maybe not so common part, because it is here where the SPDIF is used, and while the soundcard is multi channel itself (with 8 internal DAC cannels), it is not used for D/A and instead external 2ch DACs (actually one, see below) are used;

 

So, the physical SPDIF outputs from the souncard as how I use them, are 2 channel only, and I really can't think of a reason why it can't be more channels. Why ? well, because the official output from the PC to the soundcard also goes over SPDIF, but but but ... this is a kind of virtual because it's actually FireWire.

 

Things become even more vague (well, for me), when we look at the inputs to the FireFace800, and see that 8 channel data can be passed over SPDIF (which as said goes via FireWire), but also ADAT channels can be used which actually are glass links. While this is about the inputs, the outputs can be directed to SPDIF, but as I use them (see before) I direct them to 2 channels only for SPDIF and never tried differently because there's just one physical SPDIF coax output and I never tried to hook up more thn one 2ch external DAC to the FireFace. On the other hand though, there's also 8 channels of ADAT output over glass - which output is just one physical connection, and I'm sure all the channels can go over that one physical glass ouput (limited to 24/96 per channel). So, what could be on the other end ? a multi channel SPDIF input ? I think it can, but, which device does that ? IMO merely Pro devices which would be configured for ADAT again ...

 

To be more (un:-)clear, what I really have used is that multi channel in-software decoded DTS (or AC3), pass it over SPDIF to the FireFace (but via FireWire !), use 2ch SPDIF for the 2ch "fronts" DAC, and use the other 4 channels to let the FireFace D/A them internally, and have analogue outs from the FireFace to the mid, rears and subwoofer.

 

Maybe (a Pro) someone can make something of this, because I myself can't really.

 

Btw, to put some nice sauce over it all, that same multi channel "SPDIF" can be controlled in the FireFace to fine tune the sample rate by 1Hz steps, which would make it really asynchronous, and which is an as vague thing, because at the time (2004-2005) no talking was going on about the async phenomenon (and I stopped following FireFace talks long ago).

 

Summarized, back at the time in-software DTS decoding was not common at all (but TheaterTek I used could do it), and amongst thousands of TT users I was the only one who used it, lacking a processor (still never owned one). It is a kind of difficult to understand the trick and the reasons why, which latter for me was about using an audiophile DAC and the best unmolested sound (think "bit perfect" as far as that can be for the really MP3 sound coming from DTS from DVDs).

 

Btw, today (and off topic) I still follow the same principle of having the decoding in-software, but downmix all to stereo, mix the LFE explicitly into the only 2 channels I use, where the subwoofers are satellited from the low end of the speakers. The matched xovers between that low end of the normal speakers and the subwoofers, makes the LFE under 40Hz automatically going to the subwoofers only. Just 2.2 as good as it can get (incl. stereo subwoofer output !), using one 2ch DAC only, no FireFace involved, no processor and no pre-amp.

 

I hope this gives some insight, or things to think over otherwise ...

Peter

 

[bleedink]

I'm not the most knowledgable audio guy in the world...I'm afraid just about all of that was lost on me. I was very interested in what you were saying about the exclusivity issue in JRiver or windows and how one might solve that. It seemed you were saying you got it to work, but that's just you? "I am using multi channel myself (XXHighEnd) for WASAPI as well as Kernel Streaming -> don't try it, because it's not the multi channel like 6 channel audio, but technically it's 100% the same)." Forgive me if that's not what you were saying. I guess I am not sure why your multichannel is different from mine or why your problems can be solved while mine can't...that was my takeaway Peter...I hope I didn't completely miss your point.