Home»Projects »A Home-built Video Disk Recorder
November 10, 2010
January 14, 2009
October 9, 2007
November 12, 2005
February 21, 2005
September 1, 2005
April 28, 2006
September 29, 2001
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.
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.
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.
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
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.
drive for watching the occasional DVD or Video CD. Choose a quiet
Power supply is a Seasonic
200SFD with temperature-controlled fan. Again, this is chosen with
noise levels in mind.
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.
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.
Technotrend DVB-T. The tuner of the "budget" card is a lot more
sensitive than the tuner of the full-featured card.
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:
|Free to air||764||757|
A few transponders are missing because I'm not exactly in the center of their beams.
Last update page: September 1, 2005