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Deconstructing the home theater pre-processor

post #1 of 52
Thread Starter 
I wrote a blog article today about pre-processors and how their functionality might be deconstructed and split out to improve quality and ease ongoing upgrades. Thought you might be interested:
Quote:
"Ahhh....the home theater pre-pro....my thoughts on them are basically summarized by the phase "can't live with them, can't live without them"! Modern pre-pros are the brain of all modern home theaters. An AVR (audio video receiver) is essentially a pre-pro and multi-channel power amplifier in one box. Pre-pro's do a number of essential things without which it would be virtually impossible to watch movies in surround sound. What if there was a better way to go about including the functionality of a pre-pro in your system? Could it be done in such as way that would make it modular and upgradeable when new improvements in video processing and room correction make their way to market? Many people say a pre-pro is like a mini audio and video computer. If so could we use a home theater PC as a pre-pro?

You can read the rest here. Thoughts & comments?

The HTPC mentioned at the end of the blog article is going to be a test bed for evaluation of different room correction algorithms, at least those that will run in multi-channel on a PC.
post #2 of 52
Interesting...but do there exist HDMI input switching cards for PC's? It seems without these, source selection will be difficult unless the only sources you want can be fabricated with the PC. I suppose there exist cable-card tuners for PCs, so maybe you have two down (TV and Bluray), three if you've already been connecting a PC up to your receiver (or other media streaming solution).... But, can you hook your X-Box or PS/3 to it? Probably not.

That said, I've long thought that some manufacturer should release component based pre-pros. It really does break down into source selection (and up-conversion or A-D conversion on analog sources), channel mux/de-mux, room correction, volume, etc. It would seem someone would jump on that.... Though, you would need a mainboard which would impose the limits (max video/audio bandwidth available), but everything hanging off that mainboard could be component based. It'd be really neat, but I doubt they'd ever sell enough to be worth it, and it'd probably cost more than its worth. Plus, once some video format (4k 96 FPS) or something crazy comes along that blows out your video bandwidth on the mainboard, you're back to another boat anchor. But, I guess not completely...I mean, you'd have to replace the mainboard and anything hanging directly off the video bus, but...so long as the new board is backward compatible with all your existing source selector and audio components, maybe you'd be ok, still....

Humm...anyway, good luck with your adventure. Curious how it turns out.
post #3 of 52
If going this route I would choose a hardened Linux as an OS. While Windows is more popular, it's just not stable long term for a project like this. Look at Kalidescape as an example of a dedicated OS. Hell, I still use DOS for single purpose embedded projects because it's quite stable, boots fast, and royalty free. DOS is obsolete? Well I have full USB support and run can run 1280x1024 graphics. But for a project as is suggested, Linux would be my choice.
post #4 of 52
Quote:
Originally Posted by Glimmie View Post

If going this route I would choose a hardened Linux as an OS. While Windows is more popular, it's just not stable long term for a project like this. Look at Kalidescape as an example of a dedicated OS. Hell, I still use DOS for single purpose embedded projects because it's quite stable, boots fast, and royalty free. DOS is obsolete? Well I have full USB support and run can run 1280x1024 graphics. But for a project as is suggested, Linux would be my choice.

That would be an entirely different type of project project, involving development of code and custom interfaces between component.

Nyal is trying to piece together a server using standard components. For this project, Windows (or may be Mac) is the only game in town. I do agree that while he may get it to work, this will never be a completely stable and robust configuration.
post #5 of 52
I have considered all of the exact same ideas as you are pursing down to a similar build to C.A.P.S Zuma with a larger chassis. I agree with all of the points in your article. One area that you did not cover, that would be an issue for some, is extensive post-processing. For some like Lexicon owners for example, this would be a deal breaker as Lexicon has historically excelled in this area. Height channels and width channels for example are not possible.
Movie sound tracks are often very exciting. Music reproduction can be as well but those with more purist leanings seek to recreate the original event or open a window on the source. For those like myself, post-processing is not so important for music and JRSS would suffice. However, I see the continued development of post-processing and new DTS and DD formats that can add excitement to movies, action ones in particular. The only limit I see with Jriver is using the most current DTS and DD formats as they evolve. For now, I'm sticking with my Theta Casablanca for this reason. At some point I intend to build a new theater that will run 11.1 DTS Neo-X
.
However, the percentage of theater running that many channels has to be very small. Most have only a few sources and could use dacs, mine is a Theta Gen VIII S3, with built in preamp functions for additional 2 channel sources or even string several together for as many channels as they need. A server with multi-channel digital outs would work for some.

The last issue I see is the ease of use. When I mention such ideas to my friends, some audiophiles who are college educated with advanced degrees, I get blank stares. Many just don't want to think about all the steps involved setting up such a server.

I still think it’s a great idea that many should explore. I believe you can easily outperform pre-pros for sound quality. It’s the lowest price to performance ratio possible because you really are only paying for hardware and licensing tech like Dirac live.
post #6 of 52
Quote:
Originally Posted by Nyal Mellor View Post

I wrote a blog article today about pre-processors and how their functionality might be deconstructed and split out to improve quality and ease ongoing upgrades. Thought you might be interested:
You can read the rest here. Thoughts & comments?

The HTPC mentioned at the end of the blog article is going to be a test bed for evaluation of different room correction algorithms, at least those that will run in multi-channel on a PC.

Nyal, you should stay on top of what Ted is doing and reporting on Computer Audiophile. Basically sending MCH high rez over USB (he does this with DSD, but it works with LPCM as well), which then runs to a USB hub and feeds multiple USB DACs. The trick is in the USB driver software, which somehow maps the channels to individual DACs. If you do down this path, you would not need MCH Lynx card and could use USB DACs. He is doing this with Myteks, which appears to be a very competent DAC in the $2K price bracked, which is probably the sweetspot for this type of application. It would be even nicer, if you could mix and match and use a higher grade DAC for mains.
post #7 of 52
Thread Starter 
Thanks for all the thoughts everyone. Some good points here..I'll summarize, as much for my own benefit as for thread readers:

- difficulty (impossibility?) of using non-PC sources such as game consoles
- lack of availability of surround post-processing algorithms such as DTS Neo X
- ongoing ease of use and maintenance overhead issues due to use of Windows as OS

And I don't disagree with any of it, this whole HTPC thing is a proof of concept. I have had my own doubts from the very beginning, particularly about the maintenance and overhead issues. I have a Mac Mini music server that I use for two channel and that is only 'ok' in terms of stability. Certainly for most of my customers I tend to steer them towards embedded Linux type solutions such as the Bryston and away from the general purpose PC as music server route.
post #8 of 52
Thread Starter 
Quote:
Originally Posted by edorr View Post

Nyal, you should stay on top of what Ted is doing and reporting on Computer Audiophile. Basically sending MCH high rez over USB (he does this with DSD, but it works with LPCM as well), which then runs to a USB hub and feeds multiple USB DACs. The trick is in the USB driver software, which somehow maps the channels to individual DACs. If you do down this path, you would not need MCH Lynx card and could use USB DACs. He is doing this with Myteks, which appears to be a very competent DAC in the $2K price bracked, which is probably the sweetspot for this type of application. It would be even nicer, if you could mix and match and use a higher grade DAC for mains.

Hi Eric do you have a link? Are you talking about Ted Brady or someone else? I don't frequent CA much any more...
post #9 of 52
Quote:
Originally Posted by Nyal Mellor View Post

Hi Eric do you have a link? Are you talking about Ted Brady or someone else? I don't frequent CA much any more...

Check this out:

http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/first-multi-channel-dsd-playback-solution-mytek-14946/
post #10 of 52
Quote:
Originally Posted by edorr View Post

That would be an entirely different type of project project, involving development of code and custom interfaces between component.

Nyal is trying to piece together a server using standard components. For this project, Windows (or may be Mac) is the only game in town. I do agree that while he may get it to work, this will never be a completely stable and robust configuration.

So it sounds like he will focus on application software and use off the shelf hardware. I can't disagree with that for the initial product. And if the price point is right, many including myself will take a serious look at it.

But I don't think this will be much competition for the processors discussed in this forum. To some of these guys, cost and obsolescence is not the issue. And they won't be happy with an "engineering project" for a processor. They want shiny panels and slick flawless operation.

Still I think it's a worth while endeavor.
post #11 of 52
Quote:
Originally Posted by Nyal Mellor View Post

I have had my own doubts from the very beginning, particularly about the maintenance and overhead issues.
That's been my experience as well when talking to friends that have gone that route: the HTPC itself (maintenance, etc) becomes a hobby unto itself. If your proof of concept experiment finds a way to minimize the hassles, then that would be helpful.
post #12 of 52
My initial statement that Windows is unstable is probably a bit unfair. But Windows is it's own worst enemy. The product may function quite reliably in the lab and inside the factory. But people then say, "Hey, it's just a windows PC so I'll load my EMAIL software and it wouldn't hurt to run a few games if I'm not using the advanced audio features. And then let's not forget the biggest Windows stability killer - "This is so cool, I can surf the net while processing audio in the background." Even if you shut your browser off the computer has probably already been infested with processes that may be harmless in an office environment but can kill real time processing signal processing.
post #13 of 52
Quote:
Originally Posted by Glimmie View Post

My initial statement that Windows is unstable is probably a bit unfair

Unfair but true. I run just JRiver on a dedicated PC (CAPS 2.0) with everything stripped out, no internet, no email, no anti-virus. It still crashes.
post #14 of 52
Something else that is appealing is that possibility of not having to spin disk with the server approach unless that is your choice. All of my audio disc are already ripped. Blu-ray seems like a bit of a hassle, because of the space requirements. That should change.
post #15 of 52
Thread Starter 
Quote:
Originally Posted by edorr View Post

Unfair but true. I run just JRiver on a dedicated PC (CAPS 2.0) with everything stripped out, no internet, no email, no anti-virus. It still crashes.

That happens with OSX too. I think it is just the consequence of using a general purpose OS rather than something specifically for the task!
post #16 of 52
Quote:
Originally Posted by Nyal Mellor View Post

That happens with OSX too. I think it is just the consequence of using a general purpose OS rather than something specifically for the task!

I know. Small price to pay for having access to dirt cheap very powerfull HW and SW. My Linux based Trinnov processor (just a dedicated special purpose computer) has been humming along for months without one single crash, but costs a multiple.
post #17 of 52
Thread Starter 
Quote:
Originally Posted by Glimmie View Post

So it sounds like he will focus on application software and use off the shelf hardware. I can't disagree with that for the initial product. And if the price point is right, many including myself will take a serious look at it.

But I don't think this will be much competition for the processors discussed in this forum. To some of these guys, cost and obsolescence is not the issue. And they won't be happy with an "engineering project" for a processor. They want shiny panels and slick flawless operation.

Still I think it's a worth while endeavor.

Agree...BTW no intention of a commercial product at this point.

If it works out and people want to pay me to build one for them I will do or consult with them at an hourly rate to help get it set up I will do (obviously I need to figure out how to do it first!!) but at this stage it is purely a proof of concept. I thought it would be a cool thing to put together and see what the results were.

Couple of reasons I am doing this:
- I hope it will be the front end of my demo system and it will do most (not all) things the DataSat RS20i in a more modular way and a more down to earth price. I will I think be able to compare it against a RS20i at some point as my local rep should be able to get me a loaner
- I am trying to make my demo facility a dual purpose HT / music room and am not convinced on using a pre-pro for two channel. I currently use a Mac Mini running Pure Music as my source and I don't see any reason why this new HTPC can't replace that so I have one front end for both music and movies. The two channel system will run off a DEQX HDP-4 BTW.
- So I can do comparisons of the 'PC only' room correction algorithms that are out there (AudioLense, Acourate) vs. the ones built into pre-pros

I think I will be 'open-sourcing' everything about the design and build via blog posts as it's not likely anything I'm doing at this stage will be proprietary. Just thought it would be cool to share the process and results with the community.
post #18 of 52
Quote:
Originally Posted by Nyal Mellor View Post

- I hope it will be the front end of my demo system and it will do most (not all) things the DataSat RS20i in a more modular way and a more down to earth price. I will I think be able to compare it against a RS20i at some point as my local rep should be able to get me a loaner

If you run a copy of Dirac Live on your HTPC and use superior DACs than the ones in the Datasat, you should be able to beat it....
post #19 of 52
Quote:
Originally Posted by Nyal Mellor View Post


I think I will be 'open-sourcing' everything about the design and build via blog posts as it's not likely anything I'm doing at this stage will be proprietary. Just thought it would be cool to share the process and results with the community.

I'll play for sure!
post #20 of 52
Are you going to run a higher end video card,GPU? When I have investigated, it seemed like all of the ones needed for Madvr's best processing were noisy. Quiet is a relative term and what is quiet for gamers was not for a dedicated noise controlled room.
post #21 of 52
Water cool the video card, and cpu a la steiger Dynamics' Leet htpc.

Leet.jpg 396k .jpg file

And/or better yet, have the av rack outside the theater.
post #22 of 52
Thread Starter 
Some progress to report:

The HTPC is built and completely silent, JMRC is installed and I am using the DSP in JRiver to get 12 output channels over the Lynx AES16e card at 24/48. I did some minor Win 8 optimization, nothing crazy. Everything is stable, CPU and memory utilization are ~10%, so it should have legs for trying out Dirac Live and the other room correction algorithms. The main issues I have had so far were with getting Win 8 installed from a USB stick and getting the Metric Halo LIO8 I am using for 8 of the channels set up.

I have some open questions about the video side for the guys at JMRC (unless someone here can describe how to go about configuring the Intel integrated graphics in the new mobos - I have the DH77EB and how to set the video levels) but once those are finalized I will be writing a blog post detailing all of the configuration.
post #23 of 52
That is what I am using right now. I am slowly abandoning the pre-pro and using the HTPC as the one and only control center for everything. The configuration will be Jriver + DRC Software (most powerful there is), Lynx AES16e MCH output to the one and only Metric Halo LIO8 (amazing tool and DAC and you won't find better specs ANYwhere). Yet, forget Dirac Live since there are better DRC packages out there. E.g. Audiolense.

Want HDMI switching? Here is a solution that might work. Connect all your devices to an HDMI (with remote control) hub and then get one of these:

http://www.aes-hdmi.com/hdmi-2a.html

Then from this (I think about $1800) to the Lynx AES16e inputs in the HTPC, then to the Jriver audio engine after convolution and finally output to the Metric Halo and then to the speakers.

You can do whatever you can imagine with such a configuration and this is what I am putting together. Yet, you can upgrade the LIO-8 ($700) with 4 preamps for microphones (best you can find) add a good precision microphone like Earthworks M30 (I got it. Its great) and get yourself and truly accurate Room Measurement system down to single digit Hz.

This is neither cheap nor for straightforward to use though and most will be put off but hey! Its the most powerful tool you can get over tuning your HC audio.
post #24 of 52
BTW everything is done in the digital domain and whatever is fed to the Metric Halo is final processed signal. The Metric also has amazing EQ capabilities, the best converters out there and can also do any summation or splitting of channels you wish (it needs a Mac to tune).
post #25 of 52
Thread Starter 
Quote:
Originally Posted by JargonGR View Post

That is what I am using right now. I am slowly abandoning the pre-pro and using the HTPC as the one and only control center for everything. The configuration will be Jriver + DRC Software (most powerful there is), Lynx AES16e MCH output to the one and only Metric Halo LIO8 (amazing tool and DAC and you won't find better specs ANYwhere). Yet, forget Dirac Live since there are better DRC packages out there. E.g. Audiolense.

Want HDMI switching? Here is a solution that might work. Connect all your devices to an HDMI (with remote control) hub and then get one of these:

http://www.aes-hdmi.com/hdmi-2a.html

Then from this (I think about $1800) to the Lynx AES16e inputs in the HTPC, then to the Jriver audio engine after convolution and finally output to the Metric Halo and then to the speakers.

You can do whatever you can imagine with such a configuration and this is what I am putting together. Yet, you can upgrade the LIO-8 ($700) with 4 preamps for microphones (best you can find) add a good precision microphone like Earthworks M30 (I got it. Its great) and get yourself and truly accurate Room Measurement system down to single digit Hz.

This is neither cheap nor for straightforward to use though and most will be put off but hey! Its the most powerful tool you can get over tuning your HC audio.

Do you know how the HDMI-2A handles the protected audio path? I guess everything would be downsampled to 16/48 ?
post #26 of 52
To be honest I don't have the HDMI-2A so I don't know the exact details yet, I am using the HTPC 95% of time as a single source for everything but still have an Onlyo 5507 Pre-pro on the shelf just for contingency. Perhaps we should contact them about the details. In the other hand you can always let the source do the decoding to PCM and then send it to it.
post #27 of 52
Quote:
Originally Posted by Nyal Mellor View Post

Do you know how the HDMI-2A handles the protected audio path? I guess everything would be downsampled to 16/48 ?
Protected audio path is a PC concept so it doesn't apply to such a piece of hardware. I think what you mean is that unprotected digital outputs are restricted in resolution which is correct. HDCP rules require that digital outputs be no better than 16/48. This device claims to output 96 KHz. Two things are possible: 1) it is violating the HDCP license agreement and you would hope that they are too small for anyone to notice and force them to change or 2) it only puts out 96 Khz if you feed it non-copy protected content over HDMI which in your application means this won't work.

I would contact them and ask.
post #28 of 52
Or could the HDMI-2A not be HDCP compliant at all? Meaning it doesn't work at all with HDCP material?
post #29 of 52
By doing this I assume all Blu ray playback would be through Jriver? I have not used jRiver, but have been a long time HTPC / TMT5 user. The video fidelity was always fine, but I often wondered if the core HTPC settings for the video were correct before sending off to the display or Lumagen processor and then calibrating with my Spectro and Calman 5. Once I switched to the Oppo player I kept my ability to have disc and ISO playback of my Blu Rays, but also knew that the Oppo would output "bit perfect" video that is faithful to the source.

With all the places in the HTPC video chain to end up manipulating the signal (video card drivers's software panel / LUT, Jriver settings, etc... how does one know they are outputting a baseline "bit perfect" signal from the HTPC? Or does using MadVR bypass a lot of that? If that is the case, are the MadVR "baseline" settings known to be faithful to the source?
Edited by hifiaudio2 - 3/7/13 at 8:07am
post #30 of 52
Thread Starter 
Quote:
Originally Posted by hifiaudio2 View Post

By doing this I assume all Blu ray playback would be through Jriver? I have not used jRiver, but have been a long time HTPC / TMT5 user. The video fidelity was always fine, but I often wondered if the core HTPC settings for the video were correct before sending off to the display or Lumagen processor and then calibrating with my Spectro and Calman 5. Once I switched to the Oppo player I kept my ability to have disc and ISO playback of my Blu Rays, but also knew that the Oppo would output "bit perfect" video that is faithful to the source.

With all the places in the HTPC video chain to end up manipulating the signal (video card drivers's software panel / LUT, Jriver settings, etc... how does one know they are outputting a baseline "bit perfect" signal from the HTPC? Or does using MadVR bypass a lot of that? If that is the case, are the MadVR "baseline" settings known to be faithful to the source?

That's one of my key questions too. Certainly there are a lot of places the signal could get modified or changed. The only real way to know would be to test. How on earth do you test video bit perfect, if such a concept even exists??!
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