Past EED rants


Live leaderboard

Poker leaderboard

Voice of EED

Friday 20 April 2007

PC Build - Call for help [Spiny]

I'm looking at building an HTPC into a rather nice case to go under the TV (see below). The trouble is, this isn't as easy as building a desktop. If anyone has any suggestions to my conundrums below, I'd appreciate it. I guess the troubles alll start with the mobo...
  • Motherboard : Abit Fatal1ty F-I90HD ATI Micro ATX (+ HDMI Radeon 1250 with AVIVO, - 1x PCI). Seems to be the only decent C2D board I can find with a half decent graphics processor and HDMI.
  • GPU: I'll be adding an nVidia 8600, probably fanless at a later date as I don't anticipate the need until the bluray drives come down to non mortgage levels. These look great in principle and nVidia reckons they'll take 100% of H264 decode away from the CPU as well as provide all the other Purevideo trickery.
  • Sound card: There's on board sound in the mobo, but to get 2 channel over the optical out will I need an add in sound card? I may want to do this anyway in order to take advantage of Dobly Live to convert say AAC 6 channel to ac3 on the fly.
  • TV Card: With the PCI slot left I'll need a PCI-E TV card. there's this Terratec one, but it dosen't work with the Vista media centre. Hauppage only do PCI.
  • RAM: 1Gb should do but Wendel's Wonder dosen't support x4 device width RAM. Whatever that is. So do I get "CAS 5-5-5-15" or "CAS 3-3-3-12"?


  1. I've been doing this stuff for awhile as you know but rather than make a PC presentable in a fanny case, I've just had it in a case behind the couch out of sight. So I don't have much to add on the gay case thinggy. However there's a few things I can offer an opinion on.
    The vid card stuff. Seriously, forget hardware accelerated rah rah. It's probably only accelerated if you use their codec which will have limitations. You'll be using various regular software codecs and any decent C2D machine has the grunt for it. So unless you're going to play games, I wouldn't even bother with a fanny vid card. Second the sound card. I don't quite understand your delimma. You got two ways to do it, either passthrough the DD and feed into an external decoder, which depends what you got, or rather more usefully, just do it all in software on the PC and feed all six analog outputs to your PC. This is more useful because again, you just use software codecs, you wont be left high and dry by whatever stuff your AV amp may or may not decode.
    Vista media centre is pretty cool. Use whatever is compatible with that but it seems like that's what you're doing. 1GB is actually getting a bit thin on the ground for Vista, it's like having about 768MB for XP. That's fine if all you're doing is the TV stuff and all that but if it's more of a server, if you're running torrents, the odd little server app and that sort of thing, I'd probably push the boat out on the RAM. Bugger the timing, just buy regular cheap stuff. Do not piss around overclocking machines like this would also be my advice. You want it to be cool and stable and you don't need the performance anyway.
    What are you looking at for control? Some wireless gear obviously, I'm curious what though. I use a Logitech Dinovo just because I had one lying around.

  2. The case is a bit bling as it's going under the TV to replace dvd/xbox/pvr so needs Wife Acceptance Factor.
    The audio will be going into my Denon AV amp, hence the preference for S/PDIF over lots of analog cables. (More WAF). What I'm clueless about PC audio at the moment is if you're playing a stero source, say mp3, will that still be delivered over the S/PDIF as 2 channel. If so then I'm happy.
    This is the nVidia market-speak on PureVideo HD. I just kind of assumed I'd need extra grunt down the road for higher bit bluray stuff. But that's further on down the road, probably 12 months or more.
    The RAM question's just about what works really. The manual for the mobo specifically states it dosen't support 4-4-4-x RAM. I usually head over to crucial at times like this to use their memory finder but the board's not listed at the moment. I won't be overclocking, but good point on the amount.
    Keyboard wise I'll probably be getting one of these and an MCE remote (the keyboard needs the sender).

  3. The bitstream that comes out your optical port can basically be set to stereo or you can disable that and set the output of a codec to send the bitstream 'passthrough' via optical. Mixing the two together is tricky since if you have regular Windows stereo audio out the digital jack, this needs to be disabled to passthrough multi channel. The bottom line, seriously, is that it's better to do this with analogue. I don't think WAF is a factor, the cables are behind the PC and AV amp, shouldn't be visible at all.
    I guess you need some tied-in solution for Blu-ray since it's all getting very weird with the locked playback software, HDMI and all that. I'm kinda more talking about playing back high-def shit you can download. At any rate, if you had one of those vid cards and it sorted Blu-ray, then it wont stop you from running regular software codecs to play the downloaded stuff I guess so it's not a waste. You could safely worry about it when you can buy a Blu-ray drive for less than gigabucks of course, as you say. On the other hand, things might have changed a lot by then.

  4. SPDIF is a stereo (well actually up to 4 channel but let's stick with stereo) format so given that you've got SPDIF out on the PC and SPDIF in on the denon which is pretty serious kit you're sorted. Just use your local hi-fi shop to give you the right cabling. Only other consideration is that SPDIF likes short distances from a cabling perspective but sounds likes that not an issue.
    Digi is definitely the way to go in your case imho considering the Denon will have the best D/A A/D converters in your setup. Lurks comments on software problems may be a stumbling block however but on a decent sound card / output it should be controllable

  5. Woah, bogus info alert. SPDIF is not stereo or 'up to 4 channel'. It's simply a digital interface that may carry 2 channel, 4 channel or 'compressed' audio. The compressed audio is the key bit here. This is how, for example, you connect something like a DVD player to an AV amp and get full surround because dolby digital and/or DTS can be transmitted along yer regular SPDIF cable. The stuff about cable lengths... if you use copper, the line length is bloody massive. If you use optical, it's generally shorter. There is no good reason for optical other than it being an audiophile wankfest. But anyway, it's not likely to be an issue.
    The output *is* controllable on a decent soundcard, however you will need to go in and switch it when you want to, say, just use the TV sound card through the digital jacks and then switch it again when you want to watch a downloaded TV episode or a DVD so that you get a dolby digital stream going to your amp. There's not, to my knowledge, some easy or automatic way of doing this and I've tried on several sound cards and christ knows how many audio drivers.
    One workaround may be this: Use both digital and analog and then just switch between them on your amp. For example set the sound card stereo regular output to analog and jack that into your amp, then make sure SPDIF is disabled and then enable SPDIF passthrough in AC3filter and your DVD playback software. But if you want to jack off to audio quality, and rub spunk on your idol to Denon, you're actually better off doing the reverse. Anything of decent fidelity will be stereo, so you'd prefer to have that digital to your amp and then use your full three cables for six channels of analog audio for DVD and Media Player Classic etc. That solution is the most amount of cables (four total) and the highest quality and most flexible way of doing it. The Denon might not do DTS so if you like uber concert DVDs for a start, you just wont be able to do this digitally.
    There is a kind of way of doing it that Spiny eludes to in the first blog, which is using one of these mobos that has a Dolby Live encoder, basically taking all your audio and creating a dolby digital stream on the fly (like an Xbox does) but seriously, the loss of quality when doing this kind of thing is much greater (AC3 shitty compression even when listening to a CD) than any splitting hairs differences between DACs.

  6. I haven't got the first clue how you think the phrase "Woah, bogus info alert. SPDIF is not stereo or 'up to 4 channel'. It's simply a digital interface that may carry 2 channel, 4 channel or 'compressed' audio" is contradictory of remediating of my comments above. We all know it's a digital signal not an analogue one which can carry 1 to 4 channels. Shall we try not to condescend quite so much on our clannies please - mmmkay?

  7. It's contradictory alright because I say 'or compressed'. It doesn't have to carry 1, 2 or 4 fixed digital channels. It can, and frequently does, carry compressed audio instead of any number of channels. AC3 and DTS digital bitstreams, for example, which are most often 5.1. I'm not condescending, you went and advocated the opposite of what I said based on stuff that's not quite right - what more can I say?

  8. Ok I don't know what I'm missing here - Spiny's question was "[will] a stero source, say mp3, will that still be delivered over the S/PDIF as 2 channel. If so then I'm happy."
    My answer was yes - stereo sources will be delivered in stereo and therefore the Spin0r should be happy.
    As to the rest, I understand compression vs channels. SPDIF will carry up to four channels of signal as a practical guide for people in the real world. Sure, since it's digital you can compress, combine or do whatever the hell you like with a signal within a channel. But that's all I meant.

  9. Well, alright. I don't disagree with what you've said in answer to spiny's question on the simplicy of playing back Mp3s in stereo. However I don't think it was unreasonable to point out that SPDIF is not 'just' stereo cable and that there are some very real ramifications of using it in the context of things he's said he wants to do. This lies at the heart in why we've both given him differing advice.
    By saying "SPDIF will carry up to four channels of signal as a practical guide for people in the real world", I still don't agree. SPDIF still carries more than four channels. Like when people plug in a DVD player to their AV amp and I don't think that's out of the expectations of most people in the real world? (Technical note, when the SPDIF stream is set to compressed data, it doesn't use 'channels' at all - it's kinda in channels of uncompressed audio data mode or compressed bitstream mode)
    Anyway, the key point I'm getting at is that you have to set a sound card's SPDIF port to one of two mode as hinted at above: One, a simple uncompressed digital stereo mirror of everything the soundcard is playing out the output mixer. Two, disabled for Windows sound output and to be driven by third party software directly such as AC3filter or DVD playback software. For this application you actually want to do both, so it's a pain in the arse.
    Fortunately sound cards have analogue and digital connections so you can use both (but then you need to switch on your amp) or, like I said in the first place, just use analogue and you don't need to switch a thing. So, aren't you setting something similar up at the moment with some outrageous plasma and all that? What are you doing PC wise?

  10. I must say I'm a bit confused on this. This must be a software problem to have a possible contradiction in place. Cos at the end of a day of course a digital connection is a digital connection sending 1's and 0's. Sure ok the third bit in a SPDIF bitword if unset means '2 channel' and if set '4 channel' and therefore there's a 2 channel / 4 channel paradigm set in the bitword format. But it's all pretty meaningless right - it's digital - so for any given notional channel you could have 101010 be decoded as;
    Lch 1Rch 0Lch 1Rch 0Lch 1Rch 1
    Lch 1Rch 0Centre Chn 1Lch 0Rch 1Centr Chn 0
    or indeed
    Lch 1Rch 0Centre chn 1Rearlch 0Rearrch 1Sub 0
    And that's per piece of wire depending on however you told the software interpreting the hardware input to 'consider' the sequence of bits....
    So I don't understand the above. The SPDIF out in Lurks scenario 1 or 2 comes out of the same SPDIF hardware outputs on the soundcard - whether something is 'windows sound output' or 'AC3Filter or DVD' is software routing and nothing else surely?
    I need to get my head round this because indeed I have to sort my soon to be installed stuff out!

  11. Here's the final build. Apart from the GPU, it kicks my gaming rig in the nuts. Looks like I'll end up just seeing what's easiest to live with for switching the sound. The amp won't be handling the video switching, so it's doable all ways above. It's within my (not incosiderable) programming powers to write media centre plugins, so I can possibly switch output using the media centre GUI.Thanks for the eplainology chaps. Antec Fusion HTPC Case £95.99 Abit Fatal1ty F-I90HD ATI Micro ATX £64.99 Intel Core 2 Duo E6600 £129.99 Crucial Ballistix 2GB (2x1GB) DDR2 PC2-5300C3 667MHz Dual Channel Kit £99.99 Zalman CNPS7700-CU Ultra-Quiet CPU Cooler £22.99 Samsung SpinPoint T HD501LJ 500GB £72.99 Hauppauge WinTV Nova-T-500 Dual Freeview TV Tuner £54.99 Pioneer DVR-112DBK £17.99 Microsoft Windows XP Media Centre 2005 Remote Controller £19.99 Microsoft Remote Keyboard for Windows XP Media Center Edition £29.99 Microsoft Windows Vista Home Premium £63.99 Total Inc VAT & Delivery £804.69

  12. Yeah, it's sort of a software problem. There's yer two modes right, as I pointed out above. The plain jane uncompressed audio SPDIF stuff is supported by any amp going if it's got an SPDIF input so no problem there right. The problem is, when it's in compressed audio mode, it comes down to whether your amp supports that compressed audio or not. Many, but not all, surround AV amps will support surround sound via dolby digital aka AC3. Used on, I dunno, 90%+ of DVDs. And that will suffice. However there's the rarer better quality DTS which is supported on rather less equipment. SPDIF in compressed mode doesn't specify what the bitstreams are. That's up to the gear either end.
    But, the key point there is that regular windows audio - like say if you're playing something in Winamp, can appear as a plain jane digital signal on the output of your sound card. That's fine. However if you want to get sound from a DVD played on your PC to your amplifier, that plain jane mode wont suffice unless you just want to downmix to two channel and hear the DVD in stereo (a common approach by all accounts).
    So in a smart world, your sound card would switch from uncompressed to whatever right? Except that it doesn't. You need to go in and switch the mode in the sound driver for your hardware. Windows has no ability whatsoever to switch the sound card between uncompressed audio and AC3. It's not entirely window's fault (although it'd be nice if Microsoft took a goddamn stab at it). SPDIF isn't really designed for you just to switch modes on the fly like that. It's really supposed to be thought of as a cable to do a particular job, to connect two different devices.
    So these drawbacks make it easier to do the whole log on the PC and just grab the analog outputs. Then you'll get stereo out your stereo stuff and surround out your surround stuff and your amp is none the wiser. It also means you can fiddle with the individual levels of each channel on the PC, which is convienient, and - get this - you could fire up a game on your box and have it come out in proper multi-channel surround sound. You gotta see Half-Life 2 on my projector with the surround shit going on, it's just mental.
    Back to Spiny's stuff. Another reason for favoring analogue is because new stuff might come along which your amp doesn't support, specifically stuff in blu-ray. Again, the audio decoder in your playback software will absolutely ensure that it supports a multi-channel sound card by decoding it directly. Where as this stuff may not, probably wont be, supported at all on a garden variety AV amp. And indeed, it could well be that Blu-ray software refuses to give you the raw digital output also, given the DRM nightmares of the platform. Couldn't swear to that, but it's distinctly likely.
    I would recommend, if you've got uber gear and audiophile tendencies, to go with the dual approach I mention. Use an SPDIF cable just for stereo stuff so you can listen to your CDs direct to your flash amp. So you can press a button on your amp to go 'direct' as it were, or you stay in analogue mode for surround sound.
    Oh yes, the difference in quality between doing that on your amp and doing it on the sound card wont really be constrained by the difference in quality of the DACs but rather the inherent noise you can get out of PC hardware. It's an electronic noise nightmare inside a PC and hence a bad place to put a bit of high-fidelity kit normally. However decent sound cards boast some pretty phat SNR and do a pretty good job of eliminating noise, but it's still going to be there in some tiny amount that you'll hear if you wind the volume control right the way up. I've found that onboard audio is significantly noisier by comparison so that's worth baring in mind. SB card might pay off but it's loaded so much with crapware these days in so many ways (Creative seriously pander to consumers in a shocking way and have very few audiophile morals whatsoever) that actually the best bet might be some nice add-in sound card with a phat CMedia chip on it or some such. Low noise, great surround sound support and no crapware.

  13. Nonsense. Use the SPDIF and choose that as the default output in Windows. mp3's will play 2 channel (unless you upmix to DPLII through something like ffdshow audio or AC3Filter) as PCM and pass windows sounds to the amp as you'd expect.
    For AC3/DTS you again use AC3Filter or ffdshow audio and set them to SPDIF passthrough mode. This sends the source signal over the same SPDIF to the amp direct - Windows won't touch it.
    The amp will autoswitch accordingly when it sees the different signal types over the cable.
    No need to do any of this analog stuff - then you're reliant on the PC to do the decoding (extra cpu) and the issues Lurks mentioned in the last para.

  14. The spanner in the works is if you have SPDIF as the output in windows, you can't tell AC3Filter or ffdshow to output SPDIF passthrough, well you can but it doesn't work. Because the SPDIF output is in use already. You have to disable it first. That's the case on at least a couple od different audio solutions, onboard, add-in CMedia cards etc. I've not tried it on Creative SB, maybe it has a more elegant solution?
    I've also seen no less than 3 amps that were deeply unhappy in switching uncompressed audio and AC3 on the fly. May be the SPDIF source, but the point remains - it's a bit touch and go. As for analog, CPU decoding time for audio is absolutely trivial. That's like the least relevant factor in any of it tbh.

  15. Both Soundstorm in my HTPC and my laptop's Realtek both work flawlessly when set to SPDIF and passthrough works fine. I know some versions of AC3Filter have had SPDIF passthrough issues on certain kit, but ffdshow audio has always worked flawlessly for me.
    If an amp can't switch on the fly, that's a bad amp ;)
    You're right that analog avoids this problem, but you are of course at the mercy of noise and signal loss from the cabling - probably not a big deal, but and SPDIF connection is always going to be preferable.

  16. Noise and signal loss somewhat of course but to me the big win is the use of the Denon's DAC rather than the absolute piece of shit that will do the DAC conversion on your pc soundcard.

  17. Well, the cinema rig's up & running and everything with the audio just works out of the box. Hooked up via optical SPDIF the receiver gets a Dolby signal when playing DVDs and stuff with an AC3 soundtrack & plays normal stereo sources as Pro Logic (or whatever I override the processing to with the amp controls).
    Full HTPC blog in a while when I've worked out some kinks. Summary (Vista - "not so loveley")