Home Theater PC

System hardware and software

For hardware the following have caught my attention:

GIGABYTE GA-E7AUM-DS2H microATX mainboard

Has on-board Nvidia GeForce 9400 GPU, HDMI and DVI output jacks with HDCP copy protected outputs support for playing Blu-ray content. Seems an ideal combination and eliminates the need for a separate video card. 9400 should be plenty fast enough for HD video playback. 9400 reportedly runs somewhat hot, so a replacement heatsink could be useful. Mainboard uses standard and common dual channel DDR2 800 PC6400 DRAM with Intel Core 2 dual or quad processor. It supports Front Side Bus rates at 800/1066/1333 and overclocking, but for thermal survival 800 would be better.

Most importantly the 9400 has support for Pure HD, which means Blu-Ray playback is fully-supported along with HDCP copy protection (under Windows) via HDMI and DVI video outputs. The 9400 also has full hardware offload for HD playback:

Breathtaking High Definition Video Playback
Experience full-spec playback of your favorite Blu-ray titles. PureVideo HD offloads 100% of movie playback for all HD video formats (H.264, VC1, MPEG-2), delivering stunning, stutter-free video with outstanding audio fidelity.

which means that in principle a 1.8 GHz processor is enough. Without hardware HD support, a 3+ GHz CPU would reportedly be needed for HD playback. See the Hardware section of the Mythbuntu installation manual.

Antec Minuet 350 case

Compact microATX case with 350 Watt power supply, 1 external 5.25 drive bay for Blu-Ray / HD DVD drive, 1 external 3.5 inch bay for card reader, 1 internal 3.5 inch bay for hard disk. The case is notably thin at under 4 inches and comes with feet for vertical orientation like a very thin, small tower computer. It can also sit flat like a desktop case, but would seem much better thermally if vertically-oriented with the feet so that the heat can rise and generate vertical airflow like a chimney. It's also relatively small in depth and height, so it's significantly smaller than a standard mini ATX small tower case. One possible downside is that the Minuet uses a top-exit 80mm fan, where a 120mm would be quieter but very difficult to fit into the case. Additional ventilation is provided by the power supply fan, also drawing air towards the top.

Note that the Minuet case has low-profile PCI slots. Full height PCI cards probably won't fit and low-profile slot covers are probably also needed. Fortunately the pcHDTV tuner card below is low-profile, and it comes with a low profile slot cover also.

pcHDTV HD-5500 HD tuner card

A widely used video tuner card in (Linux) HTPCs. Has support for U.S. analog (NTSC) and digital (ATSC) broadcast and cable (QAM) video transmission formats. This is a low-profile PCI card that should fit into the Minuet case. Comes with a low-profile bracket and a full-height bracket too.

Cards from Hauppague would be used for other parts of the world.

Western Digital Caviar Green 1 TeraByte SATA hard disk

Reportedly quiet and energy efficient.

Microsoft Media Center Remote Control

Widely-recommended. Lots of Chinese clones are available, but they act like a mouse and keyboard to the system and don't use lirc. A popular-selling $15 model sold through Amazon that claims Media Center compatibility is an Ortek VRC-1100 which apparently works perfectly with Windows, but requires some key remapping for MythTV. Some of these remotes apparently act as both a mouse and keyboard via two separate /dev/input s and do make use of lirc. See the wiki entry for the Snapstream firefly mini in addition to the link above for more info about how to manually configure these.

Intel Wolfdale CPU

Due to the GPU handling HD decoding on playback, the CPU generally won't have much work to do. This is especially true for recording HDTV which is already encoded in digital format and essentially copied to hard disc in digital form. The "Pentium Dual-Core" E5200 sells for about half the price of a Core 2 Duo (E8xxx) of similar CPU clock rate, but performs about the same at about the same 65 Watt design power. The reason why? They're all Wolfdale 45nm chips. The main differences between the current Wolfdale model lines are 2MB versus 3MB or 6MB Level 2 cache and 800 MHz versus 1066 or 1333 MHz FSB. Here's a table comparing the E5xxx, E7xxx and E8xxx Wolfdale cache and FSB:

CPU model number	L2 cache	FSB
E5xxx	2 MB	800 MHz
E7xxx	3 MB	1066 MHz
E8xxx	6 MB	1333 MHz

Given that very few people attempt to use hot-running, expensive memory faster than the much more common 800 MHz DDR2, the 1066 or 1333 FSB capability is largely irrelevant. Using 800 MHZ memory with an 800 MHz CPU FSB is ideal since they're correctly matched at the same clock rate. Using 800 MHz memory with a 1333 or 1066 capable CPU FSB generally means running the FSB at 800 MHz anyway in order to match the memory, so there's no benefit from the theoretically faster FSB. So the main potential difference other than cost is the smaller L2 cache, which is very likely unnoticeable in this application.

Case thermal design comments

Similarly to most desktop cases, the Antec Minuet 350 has very confused thermal management. It has two fans that both pull air upwards when used in a tower configuration. The 80mm case fan vents air out the top. The power supply also pulls towards the top, but has a small vent to the front which is wrong if it provides a path for hot air to go towards the front of the case. All that would do is heat up the things in front and recirculate the hot air to get it hotter inside the case. The front outlet also sends hot air to the top case exhaust fan which decreases the case fan effectiveness. The case has minor venting around the front bezel, a large grille stamped into the side cover over the CPU/GPU area of the main board, a large open grille over the slot covers, and a somewhat ineffective row of cooling air input slots along the bottom of the side cover. All in all, the airflow seems confused and inconsistent. It's probably meant to be used with a CPU cooler that pulls air down from the grille in the side cover, which would then blow hot air over the GPU, up to the power supply and also out the top chassis fan. Neither RAM nor the hard drive or optical drive are particularly well-cooled though they have air around them and some minor airflow. OTOH the case needed to be useable either in tower or horizontal mode, so the requirements are somewhat conflicting.

Remembering that air will take the path of least resistance, if we want to convert this case to passive CPU and GPU coolers, an air shroud will be needed. Without a shroud, the air will just get pulled directly into the fans and largely bypass the heatsinks which will offer more resistance to the flow of air. Server cases often have a shroud over the front fans and RAM and CPU to force air over them before washing cooling air over the rest of the components towards the back of the case. We can copy this idea here, but in a different direction. Given the existing fans, the only useable airflow direction with GPU and CPU passive coolers would be for the shroud to direct air over them and up into the power supply. The case fan is too far forward to reach those heatsinks. The shroud will encourage the airflow to the case fan to go over the RAM and drives at the front of the case. The upward direction is good since this is a tower case where hot air naturally wants to rise to the top of the case and cool air would ideally come in from the bottom of the case.

Mini howto and notes on setting up this system

1. IMPORTANT: DO NOT HOT PLUG THE HDMI CABLE TO THE TV OR COMPUTER OR LEAVE IT DANGLING. SUPPOSEDLY THIS CAN BURN OUT THE HDMI INTERFACE SINCE IT'S A POWERED INTERFACE. POWER DOWN ALL EQUIPMENT FULLY BEFORE PLUGGING OR UNPLUGGING ANY HDMI CABLES.

2. I installed the Mythbuntu ISO from USB flash drive, putting it on the flash using Unetbootin. A CDROM would also work of course.

3. Have a working Internet connection, Ethernet or wifi. Hardwired is generally easier. MythTV needs to install with a TV schedule data source, software update access, etc.

4. Sign up for a TV schedule data service such as Schedules Direct.

5. Configure a "lineup" in the schedule data service that defines what channels you'll be using. If not, there will be no channels defined for your user account and MythTV's use of it. Delete from your lineup any channels that are not actually available in your area.

6. Have a working video signal source connected, such as TV antenna, cable, satellite.

7. Have a monitor or HDTV connected.

8. During Mythbuntu setup, choose the "proprietary" Nvidia driver and not the much older open source one included in Mythbuntu. I think it was version 180.44 . The choice of Nvidia video driver is one of the few major configuration options.

9. Adjust the TV screen setup from the setup menu, if the MythTV graphics seem cut off around the edges. The arrows mentioned don't look anything like arrows, more like grey triangles in the upper left and lower right corners with almost no contrast difference between the grey triangles and background wallpaper. Use the arrow keys to move the triangles until the white lines start to appear then back off till they disappear. I believe enter or tab toggles between the upper and lower triangles, and the "M" key selects the menu option that lets you save the settings.

10. Configure MythTV to use the tuner hardware. For the hardware above, it's called something like "DVB DTV". Look for the pcHDTV 5500 name to appear when you select that.

11. Configure MythTV to use the TV schedule data source.

12. Disable "Onboard audio" in the BIOS. This disables the S/PDIF (IEC958) output. Apparently the system can only output two audio streams at a time, from HDMI, S/PDIF, analog. This is an unusual and underdocumented requirement.

    I confirmed that HDMI audio does not work when Onboard Audio is enabled in the BIOS, so it seems that only one can be used at any given time. This is sort of ok since AV systems are moving towards audio via HDMI, though many people still have S/PDIF receivers, etc.

13. I had to update the ALSA sound system in order to make HDMI sound work with this board. I used this alsa update script, but edited references from 1.0.19 to the current 1.0.20 version. The final stage of the script essentially does nothing when you hit "1" for "auto". That's ok. Just exit at that point. "auto" is the default so nothing actually needs to be changed.

    (The ALSA update is probably needed because the sound card software that ships with the operating system and/or the mythtv fork of it lag by much of a year, so recent hardware such as this Gigabyte board may not be in the sound configs. Sound hardware is probably more specialized and changes more often than video hardware.)

14. To get HDMI digital audio output working with MythTV for this board, go to Utilities/Setup -> Setup -> General. On the third screen set the Digital audio output to ALSI:hdmi by manually typing that after hitting enter in that field.

    There is also a selection for ALSA:spdif .

15. I did not need to set up an /etc/asound.conf in order to make HDMI audio work.

16. The stock Intel CPU fan is probably the noisiest part of the system, followed by the power supply fan. I plan to replace the CPU cooler with a much larger one, ideally passive.

17. The WD green hard drive is very quiet, but makes a "clunk" in the case when doing a head seek. Generally the hard drive is much quieter than the fans and probably not noticeable.

18. I replaced the stock Antec TriCool 80mm fan with an Arctic Fan 8 PWM fan paralleled with the CPU fan and feeding the system fan RPM header on the mainboard. Arctic Cooling fans are very quiet, especially the ones with open frames, isolation mounts and PWM for slower speeds like the 8 PWM.

19. I replaced the stock Intel CPU cooler with an Arctic Cooling Alpine 11 Pro. It's designed for 95 Watts which is much more power than the 5300, so it's significantly larger than stock and runs very cool at this CPU's lower power levels. It fits in the case nicely since it's pure aluminum and has no heat pipes. It's also much quieter than the stock cooler, with noise barely perceptable when an ear is right next to it. For all practical purposes, it's silent. Any fan is going to be louder than a passive cooler, but the fan turns slowly most of the time, and having a variable speed fan is good protection against overheating on a hot day. The fan has an open frame and is suspended in rubber mounts which any isolate vibration.

20. I replaced the smallish stock 9400 passive (fanless) chipset GPU heatsink with a Thermaltake "CL-P0444 AMD Quiet CPU Cooler" that was on closeout at Frys for about half price at $6.90. This cooler was apparently designed to quietly cool a low end AMD Athlon CPU, thus the fairly low heat capacity and wide fin spacing. Its unusually wide fin spacing (maybe 5 mm fin pitch) is good for this passive cooling application. (I removed its fan.) For passive cooling wide spacing of the fins is needed due to the lower air resistance faced by slower-moving, natural air convection. For fan-based cooling, closer fin spacing is better since air is actively forced through them. I used thermal epoxy to glue it onto the chip and had to saw off about a half inch of the fins to make it clear the CPU cooler. The other end of the heatsink does block the top two mainboard slots, but it's very unlikely they will ever be used. This is a dedicated HD DVR and the only slot used is by the tuner card further down.

21. I thermal epoxied a small chip cooler onto the exposed chip on the tuner card. The cooler feels hot so it's doing some good. Probably not necessary, but may help the chip run a bit cooler.

Temperatures and power

Tuner card runs surprisingly hot, so I moved it from the lower PCI slot to the upper one, for possibly better air cooling.

Power consumption measured using uncalibrated Kill-A-Watt:

Idle	47W
MythTV menu	49W
Full HD Recording	51W
Full HD Playback	54W
Watch HD TV	67W (includes recording since MythTV records live TV)

This is without aggressive CPU throttling, spinning down idle hard disk, etc. Given how hot the tuner card runs, it would probably be useful to depower it too when it's not needed. However the much better solution is to shutdown the entire system and wake it when it's needed for recording using ACPI. See also MythTV Power saving.