low power

Linux as a Home Theatre PC (HTPC) – Installation

Tuesday, February 23rd, 2010 | hardware, linux | 4 Comments

See Linux as a Home Theatre PC (HTPC) – Introduction for an introduction to using Linux as a HTPC. In this post, I detail the steps I used to actually install and configure the HTPC and some minor gotcha’s that cropped up in relation to audio over HDMI.

  1. Downloaded Mythbuntu 9.10 64-bit edition from the Mythbuntu site.
  2. Installed Mythbuntu using the standard configuration settings (I may reinstall with a different partitioning scheme in the future but for now, at least, I just need a partition in which to dump various bits of media).
  3. Connected the MythTV box to my HDTV using a standard HDMI cable.
  4. Ensure you are using the NVidia Restricted Driver version 180 (and not 173) in order for HDMI audio to work (there is also a newer version 190 driver but I haven’t verified that this works yet).
  5. During initial MythTV configuration, configured to use ALSA:hdmi for audo playback rather than the default. This is sufficient to have MythTV play video files loaded in /var/lib/mythtv/video correctly.
  6. While MythTV presents a nice interface, I would also like to be able to use the standard Ubuntu desktop from time to time (Mythbuntu installs an XFCE4 environment by default – you can install GNOME or KDE also if you wish but for occasional use, the standard environment works very well). To get HDMI audio working outside of MythTV (for example, when browsing), added the following to /etc/asound.conf
    pcm.hdmi_hw {
     type hw
     card 0     #  <-----  Put your card number here
     device 3   #  <-----  Put your device number here
    pcm.hdmi_formatted {
     type plug
     slave {
     pcm hdmi_hw
     rate 48000
     channels 2
    pcm.hdmi_complete {
     type softvol
     slave.pcm hdmi_formatted
     control.name hdmi_volume
     control.card 0
    pcm.!default hdmi_complete

    and then went to Applications/Multimedia/Mixer and clicked on Select Controls and enabled IEC958 2 and hdmi_volume. Back in the main mixer window, select the Switches tab and enable IEC958 2. Sound over HDMI should now be working (thanks to http://ubuntu.ubuntuforums.org/showthread.php?p=8522729 for tips on this, configuring HDMI sound output can be a little tricky for now at least).

  7. ALSA includes a useful utility called speaker-test which you can use to test your sound output.
    speaker-test -Dplug:hdmi -c2 -twav

Of course this is an experimental system – so not everything works perfectly. In particular, the TV card is not currently picking up output from my UPC cable set-top box (the set-top box includes a standard TV aerial socket on the back which I’ve connected to the Hauppage PVR-150). When I tested the system with Mythbuntu 9.04, I detected a signal from this and could view some television channels (the quality was mediocre but I didn’t attempt any tuning or tweaking) and could use the system as a PVR / DVR – one of MythTV’s key features. Since installing Mythbuntu 9.10, I haven’t detected a signal despite some efforts to configure it. I suspect a kernel driver issue but I have yet to work my way through the IVTV troubleshooting procedure mainly because I’m not very interested in this functionality for the momet at least. It’s something I’ll investigate at some stage, although in the future – I’ll probably be more interested in adding a DVB-T card to the system to avail of Ireland’s Digital Terrestrial Television.

In conclusion – things that are working well include,

  • Video playback – both in the MythTVin frontend and from the XFCE desktop (using VLC or Totem).
  • Music playback,
  • HD playback including using VDPAU. During playback of some HD samples, processor load on the system remained negligible, suggesting that the bulk of the decoding activity is happening on the 9400 rather than on the cpu.

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Linux as a Home Theatre PC (HTPC) – Introduction

Tuesday, February 16th, 2010 | hardware, linux | 3 Comments

Hi – apologies for the recent hiatus, hibernation is coming to an end, should be posting more frequently again now (also currently experimenting with both twitter and buzz).

I recently started looking into using a Linux box as a media centre or HTPC. In the past I’ve experimented with so called “multimedia drives” as a solution for managing my collection of media recordings and archived media. The drive I was using was a Lacie Silverscreen and while it worked, it did have various limitations. In particular, it didn’t play HD media and it sometimes had audio sync issues playing back media that played without problems on the PC. I assume the sync issues were the product of either a lack of processing power in the Silverscreen or possibly a lack of codecs. Newer products from Lacie (or similar products from other companies like Iomega’s ScreenPlay) have probably addressed some of these issues and there is no doubt, if you’re a non-technical user, these multimedia drives are a good solution.

In the interests of learning more about how well Linux works as a media solution, I decided to go about building one with a view to installing MythTV on it and evaluating the suitability of a Linux box as a full-featured HTPC. The first step in this experiment was to identify suitable hardware for a HTPC – key requirements for me were,

  • Noise – as a machine sitting in your living room beside your TV, the HTPC needs to be quiet. This also suggests it should run cool, it means if you have any fans in the system they won’t need to run at a high speed and/or for long. Key considerations for sound are minimising the number of fans (preferring passive cooling options such as heatsinks if they work), sound reduction features in the box (such as sound insulation and things like rubber/silicone grommets for mounting hard drives, fans and so on).
  • Performance – I want the system to be capable of playing back all possible types of media including HD video. I’d also like to have the option of encoding new media on the fly while simultaneously watching  something else. All of this means that a reasonably powerful processor and a reasonably high performing graphics card are neccesary.
  • Size – as a further consideration, I’d prefer if the unit I build is reasonably small – ideally it shouldn’t be particularly visible in the living room beside or near the TV. For this one, I don’t plan to go to any heroic efforts so I’ll prefer a conventional case over anything amazingly small. As you reduce a PC in size, you start running into heat issues and you start having to use components that have been specifically designed for smaller units – which leads to increasing cost.
  • Cost – while not the main driver, I didn’t plan on spending excessively for any particular component of the system. Certainly, a good spec HTPC shouldn’t cost any more than a reasonble spec desktop PC.

After lots of research and review reading, I finally settled on the following spec (note that in February, 2010, at least some of this hardware is well behind the curve – if you’re building a new box now you can probably find improved components for at least parts of this),

I chose the motherboard, primarily for the integrated NVIDIA 9400 graphics chipset which provides a HDMI output on the motherboard and also includes support for HD decoding in the chipset (rather than requiring the main system processor – while there is some support for such decoding on chipsets from other vendors, the support for doing this in Linux seems to particularly good with the 9400 using VDPAU). Other components were mainly chosen either because they have a good noise profile or because they give good “bang for buck”. The processor is probably overkill but was relatively cheap and given this system is a testbed for various media experiments, I’d like to have enough processing power just in case. For a typical user, a lower spec processor would be more than sufficient. A similar comment applies to the memory, it is way more than I expect to use but for the price, it didn’t make sense to purchase less. Note that the memory is standard, boring, “value” memory – I’ve experimented with high performance memory in the past and it required various tweaks such as bumping the memory voltage in the BIOS and manually setting memory timings before it performed optimally (or at all) – life is too short for this and the performance gains for a typical user aren’t really noticable (but such memory usually features impressive go faster stripes if thats your thing!

As an aside, since I build this system – NVIDIA have released their ION graphics platform and Intel have released their Atom lower power processor range. These seem to provide the basis for a good HTPC type system (as far as I know, the NVIDIA ION platform is built around a version of the 9400 chipset so it should have similar functionality to my motherboard’s chipset) but I have some concerns about how suitable the Atom processor would be for heavier duty tasks such as transcoding. As always, there is a trade-off between performance and overall size – smaller systems have less room to dissipate heat so they need to run cooler (usually with a lower performance).

For my initial foray into the area, I decided to use Mythbuntu, an Ubuntu based Linux distribution which includes MythTV and is preconfigured to work well connected directly to a TV. Mythdora is a similar idea but based around the Fedora distribution. There is no reason not to install your favourite Linux distribution and install MythTV on top of it if you wish.
My initial experiments were carried out with Mythbuntu 9.04 earlier this year but I thought I’d reinstall with Mythbuntu 9.10 on it’s recent release and document my experiences here, including detailing what works and what doesn’t. See my next posting for details of how things went.

Update: Puzlar sent me a tweet asking what kind of remote control I used with the system. The Antec Fusion case comes with it’s own infrared receiver and remote control. The Hauppage PVR-150 also included it’s own IR receiver and remote control. Since the IR receiver in the Antec Fusion case doesn’t need any additional items to be plugged into the box, I opted to go with that. The MythTV wiki contains details of how to configure the IR receiver to work properly – when I installed Mythbuntu 9.04 it required some manual tweaking but when I installed Mythbuntu 9.10 it worked out of the box without any tweaking as far as I can remember – so the standard keys like the arrows and the play/pause/rewind/forward buttons on the control do what they should do in the Mythtv Frontend and you can move the mouse around the desktop using the control also (which is a bit slow but ok if you just need to point and click on something occasionally).  I also have a wireless mouse and keyboard (a Logitech S510 but it seems to have been discontinued in the meantime) for occasional surfing and tuning of the system. I recently tried out XBMC as an alternative interface for the HTPC and that supported all the remote control functionality too (perhaps more than MythTV out of the box) – XBMC looks like a nice alternative to MythTV if PVR isn’t a requirement – I’ll be playing around with it some more.

One other note on the case – the Antec Fusion is a nice case – maybe a little bigger than I expected but it does look more like a piece of HiFi kit than a PC so it blends in well beside the TV. While I thought an LCD panel on the HTPC would be useful, in retrospect I have no need or use for this and if I was going again, I’d probably order a case without an LCD – perhaps something like the Antec NSK2480.

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No power? No problem!

Friday, March 13th, 2009 | business, hardware, linux | No Comments

Came across this nice story of someone living off of the grid in Scotland while still running a pretty well serviced network. I’d love to see what an equivalent Windows Server based environment would cost in terms of power.

The author makes a good point that what some people chose to view as a disadvantage of open source based systems – that you can choose many different components for an open source system and that you can configure them in a myriad of ways – is, for at least some environments, very much an advantage. I tend to agree. While I like to create homogenous, documented environments for my customers – I do tailor each of those environments to my customers’ requirements – rather than trying to change their processes and workflows to suit the software (an all too common problem which occurs when deploying entirely proprietary systems).

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