Monday, 8 December 2014

HTPC as PreProcessor

I’ve been living with my old school (analog) Pioneer VSX-D2011 receiver for well over 10 years now. It’s 7x100W channels have served me well in my HT but it’s very old in terms of format support, connectivity etc.

This hasn’t bothered me too much as I’ve always had a HTPC to look after playback etc. but it’s always been a stop-gap solution as I think about a receiver upgrade or something else.

Now, I’m hankering after a speaker upgrade and whatever I go for will likely need more power than a 7-channel receiver can provide, so I’m thinking separates. That being the case, I need to purchase a stand-alone AV processor or seriously look at using the HTPC as processor.

I decided to look at the HTPC as it would require the least up-front investment and I can determine if it all works with current equipment b before investing in speakers & amps.
So far, in my Home Theatre I’ve been using HTPC front ends like Plex, XBMC and, more recently, MediaPortal. Right now, the system is run from a virtual HTPC in MediaServer8.

This supports DVD/BluRay playback, outputting bitstream audio via SPDIF to the receiver and pictures to an ancient Sony CRT projector. It doesn’t support modern audio codecs such as DTS-HD and the like. It also doesn’t support DVD-A or SACD, I have a standalone Pioneer deck for those formats.

So, I’d like to look at removing the receiver from the picture (or relegating it to use as an amplifier only pending replacement with a proper power-amp). To do this, I need to work out the best way of getting sources into the HTPC, finding the best playback software and pushing everything out to an amplifier.

The only real external source I have is the aforementioned multi-format deck that plays DVD-A / SACD. This has 5.1 analog outputs plus, interestingly, an additional pair of stereo analog outs, which apparently have higher-quality circuitry.

I also have a Squeezebox with SPDIF out which I use for playing back audio stored on MediaServer8 as well as Spotify streaming content. Ideally, I’d like to retire this device as the PC should be able to playback all of this content.

And that’s it. Other sources would be optical discs which would be handled by the HTPC BluRay player and of course digital video files stored on MediaServer8.

Looking into using HTPC as pre-pro, it seems Jriver Media Center is the best route due to it’s flexibility and DSP capabilities;

I’d dabbled with JRiver in the past but never really took to it - it’s standard UI seemed overly cumbersome and the Theatre UI is not at all attractive. However, looking at it from a capability perspective, it’s clear that nothing comes close in terms of capabilities, and with audio zones now added, it’s got great potential.

It looks like JRiver MC will handle pretty much all my media playback including standard and high-fez audio, DVD and BluRay rips etc. In fact, the only thing it seems not to handle is Spotify, but I’ve found Fidelify which as a bit perfect Spotify player that can hook into JRiver ASIO output device for playback - but we’re getting ahead of ourselves!

I have an M-Audio Delta 410 PCI sound card to hand. This is quite old but a nice pro card it it’s day that sports 8x analog outputs, two ins and SPDIF in and out for digital signals. It supports up to 24/96 audio. That would give me 7.1 out to amplification but not enough inputs.

I spotted a used M-Audio Delta 1010LT for sale in local classifieds. This would add a further 8x analog outs and well as 8x analog inputs and a few digital ins and outs as well. Crucially, it uses the same drivers and control panel as the 410 so I snapped it up.

So I popped the two PCI cards into MediaServer8 expansion chassis and passed them through to a test Windows 8 VM, connected the outputs to my receiver multi-channel ins, loaded up JRiver and did some testing.

Standard audio played back OK but any high rez files were accompanied by pops and clicks which were on the mildly annoying side of frequent. I tried lost of things such as tweaking buffers and the like but nothing I did resulted in pristine audio.

Wondering of it was an issue with running inside a VM, I threw together a very simple system based on an Asus C8HM70-I/HDMI Motherboard (Celeron). With the same hardware setup, this system played audio perfectly so it was something to do with the VM.

Rather than troubleshoot the issue, I decided to bite the bullet and run the HT HTPC not as a MediaServer8 VM but as a standalone system. I had envisaged MediaServer8 as a single unified system and this was my first departure from that goal. However, as a very low power system, I am resigned to running it as needed. I’m treating it like a processor - switch it on and off as required.

I had also considered an outboard audio interface (such as an M-Audio Profire 2626) which might have given better results in a VM. Plus it supports audio up to 194KHz. However, as I am seeking to work out the feasibility of this project on a very tight budget, I’ve decided to to indulge for the moment.

Now that I have stable audio playback at all resolutions, I needed to turn my attention to getting my multi-channel audio in from SACD. I connected up the Pioneer 5.1 outs to the Delta 1010LT inputs. Et Voila, sound!

Except its either or. using the M-Audio control panel, I can listen to the multichannel in or I can listen to JRiver playback, but not both.

JRiver has an option to stream ASIO input in the file menu, but when I set it up for 6 channel playback from the M-Audio ASIO driver, it crashes.

I have found a workaround - I have written a couple of batch scripts that load up profiles into the M-Audio control panel. This allows me switch between multichannel input or JRiver output on the virtual router. Now I’ve got to find a way to switch these based on zone selection in JRiver.

So far, there’s a lot of good stuff in JRiver but I’ve got some major compromises and hurdles to overcome. I’m going to keep going at this for a while longer to see if I can make it work for me.


EggPar said...

Thanks for the thread! You've done what I hope to do so any updates? I have an older Yamaha RX-V2095 which neared the top of its' scale when I bought it. I never built out the home theater cause I couldn't afford the speakers I wanted. Anyway, I have completed the build out now and am finding that the lack of HDMI is very restrictive. Instead of buying a new AVR and be in this same situation when they come up with a new format I'd like to use the external decoder feature which allows 5.1 channel analog inputs through standard RCA connectors. I am trying to understand how to build an HTPC that will act as an upgradable pre-processor. A simple pc running Kodi (XBMC) and or JRiver (which I just discovered) but to get the outputs, I read a thread about a Lynx Audio AES16e card that would work then I saw the price... I'll read about some of the cards you mentioned here but do these cards do more that just convert the digital signal to analog? What does the decoding? All software based i.e. Jriver? Can I adjust the pre-pro card's output voltage?

Sooo much information and will I really notice the difference using an external DAC or $900 PCIe card? HELP!

EggPar said...

sooo many questions...

I want to do exactly what you've described here. An HTPC with at least 5.1 analog outs to use the "external decoder" inputs on my Yamaha RX-V2095.

I just discovered JRiver. It does all the decoding and then what does the Delta, M-audio or Lynx card do? It just provides analog inputs and outputs? They seem so expensive, is there another option? Is the card and cable all I need to make this work. I don't understand everything I read about these things but I've read that the Lynx AES16e as an example does not complete the Audio Interface alone. What else might I need?

I've been reading about pre-processors.. can I set the output voltage on a card like that?

Ultimately what I want is to replace my Apple TV2 running Kodi(barely) and use my nice legacy amp for pushing my PSB Stratus 5.1 speakers while gaining a better network player and the latest Home Theater HD formats. (not to mention future proof the whole thing)

Any updates on your htpc effort?

Peter Mee said...

Essentially, all you need is an audio card that will present analog outputs as individually accessible channels. For example, I have an old Soundblaster Audigy with ASIO drivers that supports this. Therefore, you don't need to spend a fortune on this. Some cheap USB eternal interfaces may work as well.

Looking at the more PRO cards, you get additional features like better DACs, proper RCA (or even XLR) connectors for each channel, ASIO drivers, higher sample rates and bit depths etc.

You're right, software like JRiver does the decoding of audio formats and maps the decoded signals to the audio interface outputs. The audio card converts the digital signal to analog (better DACs in the cards = better quality output).

Not sure about setting voltage on cards.

Since the above, I added an external audio interface to my system, - a MOTU 828MkII. This is a really nice solution - a studio grade audio interface that you can pick up second hand relatively cheaply. However, overall I've moved on a little and managed to acquire a decent a/v processor for decent money (a Sherbourne PT-7030). This now handles all the processing and the PC is source only. Ultimately, it's a lot easier to manage and doesn't invite constant tweaking.

EggPar said...

Thanks for the update! You are not the only one moving away from the pc as a processor. My understanding of how to build a home theater that may be more future proof has evolved. I now understand that it is best to buy separate amps so that you can add channels as technology advances (i.e. Dolby Atmos). Speakers and amplifiers being the most expensive components it makes sense to me that these be bought only once.

The easiest way to feed these amps is with a pre-processor that incorporates the digital sound processing and DACs. The problem I see with the pre-processors is that they are (generally) not upgradable or gang-able not to mention expensive.

Please help me explore the problems with the HTPC route. The main advantage should be that if the technology changes the pc should be the easiest to upgrade. Often new software is all that would be required, if not, a new PCIe card. The HTPC separates out the DACs, so, the purchase of multiple (USB) DACs (though like amplifiers, also permanent) can be expensive. To me, this sounds like a good option.

So what are the main issues with using an HTPC in this way. I read that the handshake protocol can cause problems but don't quite understand that or how to circumvent. I imagine that setting the HTPC up to be easy to use (acceptable to wife) might be a challenge. What am I missing?

My plan so far is:

1. to keep the Yamaha for it's 5.1 channel amps and maybe add a two or more channel amp in the future. (better quality amp to run mains and Yamaha handles the effect channels.

2. either buy a 5.1 channel USB DAC (I've done no real reading on this option) or something like the Xonar Essence STXII with it's sister board H6 (about $550)

3. build the HTPC with bluray, running JRIver and Kodi to serve as source and processor. (probably another $600-$800)

Given your experience would you do anything differently? Would you strongly suggest that the HTPC route is more hassle than it's worth?

EggPar said...

I don't want you to think I didn't read your post. The Sherbourne PT-7030 looks like a nice simple machine. My concern with it and others like it is that when you decide you want to play 4K video or Dolby Atmos encoded Audio, what will your option be. I am not criticizing your choice. I see the value in easy and I'm wondering if it may not be only a bit more expensive. You spend more money upfront but have a system that works and when you do buy another processor you'll get new DACs (they probably get advances also) along with the new codecs and simple operation.

I am just upset at the consumerism in this stuff. Spending 2k every 5-10 years to replace everything that is in the box... Maybe I'm being ridiculous... At least with the separates you don't replace as much as in a receiver..


Peter Mee said...

Hi EggPar

I agree with you on the PC being a more logical solution to the constantly evolving standards in that it's eminently upgradable.

However, with the evolution of Atmos, 4K, and the new audio and video standards emerging as well as licensing restrictions, I think it's going to be a while before a PC can be configured to support all of that - we have processors and receivers today that are ATMOS friendly and can be upgrded to DTS-X next year.

I'm happy to stick with my basic Sherbourne for now, build up my am and speaker capability (not to mention a 4K capable display) and move to something like a Marantz 7702MkII or 8802 next year.