A Home-built Video Disk Recorder

When building your own vdr you will have to make choices. Some of the requirements are contradictory, some of the choices difficult. This page reflects the choices I've made. The main criterion was keeping the PC quiet. Keeping a PC quiet implies keeping it cool, as fans are a major noise source. Surprisingly enough, the main source of heat is not the CPU but the DVB tuner cards. Each tuner card dissipates up to 8W. In general, the more recent tuner designs consume less than older ones.

CPU

The cpu used is a socket 478 Celeron 2.0 GHz, C1 stepping. Chosen because the worst-case heat dissipation of 52.8W - what Intel calls Processor Thermal Design Power - vs. clock frequency compares favourably with other models.
When watching TV the CPU is 90% idle; CPU temperature reaches 37ºC at an ambient temperature of 21ºC and a fan speed of 1000 rpm. Maximum temperature is about 45ºC, fan running at 1400 rpm.
A 2 GHz Celeron CPU is too slow to watch HDTV. A 3 GHz Pentium IV with hyperthreading is quite capable of showing HDTV in real time, but generates so much heat fan noise becomes a nuisance. YMMV.

Cooler

The CPU cooler is an Arctic Cooling Super Silent 4 Ultra. Reasonably quiet; does its job.

To slow down the CPU fan a temperature-dependent speed control from noisemagic.de was added.
Fan speed control

Memory

PC2100 stick
Memory is 256 mb PC2100 ram. You need enough memory to avoid any swapping, and 256 mb is just about right.
If you wish to run all user programs from a ram disk you might want to double this to 512 mb ram. Running user programs from a ram disk allows you to spin down the hard disk when not recording or watching recordings. Spinning down the hard disk lowers noise.

Motherboard

Motherboard is an Intel D865GLC micro-ATX motherboard. This is a fairly conservative choice, as I wanted a board that followed the PCI spec exactly.
The motherboard allows for mounting the PCI cards vertically; this increases system height but makes convection cooling easier.

Video

Putting a hugely powerful video card in your vdr is probably quite unnecessary. Let's consider two setups: a classic vdr setup and a more modern one.

In a classic vdr setup you don't even use your video card: you watch TV using the TV out of the full-featured DVB card; unless you happen to be installing or upgrading linux you won't even have a PC monitor connected. As the MPEG2 decoding is done by the DVB card CPU requirements are low.
The TV out of full-featured DVB cards is quite good at what it's made for: watching standard definition MPEG1 or MPEG2 streams of up to 10 Mbit/s on a conventional analogue TV. However, if you want to watch High-Definition TV, if you want to watch DiVX or MPEG4, or if your TV has a DVI or HDMI input you may want to start looking for alternatives.
A more modern approach uses your PC's graphics card. The xine, mplayer and softdevice plug-ins are different projects to watch TV on the graphics card. This approach doesn't need that much processing power in your video card either - when watching movies, all those 3D graphical features are quite useless. However, if MPEG decoding is done in software it can require a fair amount of CPU, especially at higher resolutions.
The main question is whether your video card provides the resolution you need and the MPEG hardware support you want. Look for IDCT (Inverse Discrete Cosine Transform) and MC (Motion Compensation) in the hardware spec. In linux, this corresponds to XvMC software support.
Just in case you thought that a DVI digital connection to your TV means analogue is something of the past: in the TV I'm using - a Philips 32PF9976 - the DVI connection terminates in a Silicon Image SiI905 chip; a DVI to RGB analogue converter.

You cannot use every AGP card in every AGP slot; before buying check compatibility. My personal choice is an Aopen FX5200-DV256, a fully passively cooled nVidia card. No fan, no noise.

Hard disk

Hard Disk

Hard disk is a 250 Gb Samsung HA250JC SpinPoint. Disk size determines how many hours of movies you can store. A handy rule of thumb is that one hour of standard definition TV needs more or less one gigabyte of disk space. Hence, 250 Gb corresponds to more than ten days of uninterrupted movie-watching.
This disk spins at only 5400 rpm, but I neither need nor want a faster disk: I prefer a quiet disk to a fast one. High disk speed adds nothing to viewing pleasure.

DVD drive

A DVD drive for watching the occasional DVD or Video CD. Choose a quiet one.

Power Supply

Seasonic power supply

Power supply is a Seasonic 200SFD with temperature-controlled fan. Again, this is chosen with noise levels in mind.

Infrared receiver and wake-up board

In addition to a LIRC remote control receiver you also want to switch the PC on by remote control. I'm using a ready-made microcontroller board bought from k-data (info at nospam.k-data.org) running software from Frank Jepsen. The board contains a small real-time clock that automatically switches the pc on when a TV programme needs recording. Unfortunately, documentation is only available in German.

DVB cards

Before buying a card it's probably not a bad idea to take a look at the supported hardware list in the linuxtv project. Even so, I suggest sticking to the most commonly used hardware: not all cards are equally well supported. A classical vdr setup is one with a single full-featured DVB card, possibly extended with multiple budget DVB-cards. The setup I'm using consists of two terrestrial DVB-T and one satellite DVB-S tuner. This fills all motherboard PCI slots.

Full-featured DVB-T

Full-featured Technotrend DVB-T. On-board DSP memory was increased from 2 mb to 4 mb by Wolfsoft; and a small circuit board was made to provide a SCART output. Note that this is an already aging design; the DVB-T tuner is not very sensitive when compared to the "budget" DVB-T card. Not recommended for new systems.

Budget DVB-T

Technotrend DVB-T. The tuner of the "budget" card is a lot more sensitive than the tuner of the full-featured card.

Budget DVB-S

Technotrend DVB-S.
All DVB cards were bought from dvbshop.

The local TV stations all schedule movies more or less at the same time. Having multiple tuners allows recording multiple programmes at the same time. Recording four movies simultaneously is not unusual. Six simultaneous recordings is feasible, but then the system becomes sluggish. Commercials are removed later using noad.

Should you be interested in USB DVB tuners, please note that USB 1.0 and 1.1 designs have only limited bandwidth, adequate for a single SDTV channel only. USB 2.0 tuners are a better choice; they're fast enough to record multiple SDTV channels in parallel - if the SDTV channels all use the same frequency.

The satellite dish is a a 90 cm aluminium offset dish Triax TDA88 / Flexibloc with dual Alps LNB's for Astra 19.2º and Eutelsat Hotbird 13º satellites. Channels I actually receive are:

Satellite channels received
	TV	Radio
Free to air	764	757
Encrypted	933	140

A few transponders are missing because I'm not exactly in the center of their beams.

Software

Klaus Schmidinger's vdr running on top of a 2.6 linux kernel. lirc is used for the remote control.

Case

The case is a Lian Li PC-9300 Micro-ATX enclosure. A Lian Li C01-A aluminium CD drive door was glued into place with silicone rubber. The lid, which covers case top and sides, was removed and replaced with a stainless steel mesh bought at a local hobby store. The open mesh allows convection cooling. More pictures.

Last update page: September 1, 2005

Koen De Vleeschauwer

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