January 29, 2004

A digital VCR

Since I left Sydney to work in Holland, I have been attempting to setup a scheme to watch the TV being broadcast back home. This keeps me in touch with events in Sydney, helping to ease a bit of homesickness, and giving me a wider choice of stuff to watch on telly.

The basic idea I've been doing is to use a widely available tv encoder card for PCs, and use that to generate video files of the TV programs I want to watch. As I have a server sitting in Sydney, I can use this to generate and host the files. My original attempts at this were rather unsuccessful. I made use of a bt848 tuner card, with a rabbit ears antenna to pick up the signal. Most TV in Australia is broadcast on the air, so cable is not an option for me, without paying.
Linux has supported the bt848 cards for a long time, and I had various things encoding the video, most notably RealEncoder and mencoder. These have both done quite a nice job at encoding the signal for me, and I can't really fault them. But what I have really been lacking is decent picture quality.

Poor picture quality has been caused by two things. Firstly, I never had decent TV reception. My machine has been housed in numerous locations over the years, and reception's been pretty poor in most of them. The location I was for in the longest was essentially a metal cage, and as any electronics geek knows, Faraday cages are great for absorbing radio and tv signals. Secondly, most TV cards get a lot of interference from the PC that they're plugged into, creating herringbone patterns and other annoyances in the picture.
I finally settled on a really convenient location for my server - my parents house. Using an ADSL line, I have a nice fast connection to the net which takes care of connectivity. I also have excellent TV and radio reception there - my dad is a radio ham (as am I), and has a farm of antennae on his roof. This gives me perfect reception for virtually every TV and radio station in Sydney. It also gives my parents a nice fast net connection to replace their dialup.

Whilst I was in Sydney over Christmas, I found out something very nice - all TV stations in Oz are now broadcasting DVB-T signals! Meaning that they're all sending an MPEG2 digital stream side by side with their analog stream. And this stream can be received by the Hauppauge Nova-T capture card. Things clicked instantly and I decided I just had to use the digital signal.

A short while later, I had my box installed with ADSL line and the digital TV card. With the Linux drivers for the DVB card, and the latest CVS version of mplayer, I could finally dump the mpeg2 stream to disk. Perfect TV reception at last! I'd waited years for this, and was very happy to finally have the signal I needed.

The digital signal is at 5+ megabits per second - much faster than I can send over my lowly ADSL line in reasonable time. To get it back to Holland, I convert the stream to a 500kbps DivX stream with mplayer. This takes a little while on the slow CPU, but gives fantastic picture quality, even when viewed on my 34" TV. The stereo audio is also a huge improvement over the mono signal from the old analogue card, and it has absolutely no interference which was a big problem with the analog card.

To get regular programming, I've setup a little shell script and cronjobs to record the TV shows that I want to access regularly. In my case, it's the nightly news, and The Bill. Other programs are also added as I spot them in the TV guide.

Together with my radio recording setup, I'm now able to get the full comliment of broadcasting available in Sydney, any time I want. At least one other expat Aussie gets the recorded shows, and I'm kind enough to offer any shows to other homesick Aussies - bandwidth and show size/program clash dependent!

Posted by Ben at January 29, 2004 12:16 AM


This is brillient. I don't pretend to understand the technicalities but the thought process and implementation really impress me. Keep up the good work.


PS I will pass this on to my brother in NZ if you don't mind

Posted by: Doug VK2IMI at January 30, 2004 07:14 AM
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