Digital TV hardware?

[daniel.mons at iinet.net.au]

 On Mon Apr 14 11:12 , "Senectus ."  sent:

>Sorry for entering this so late, but Daniel can you give me an idea of
>what sized machines you're talking about?
>To be able to record 2 channels at once and view a recording?
>

http://en.wikipedia.org/wiki/DVB-T

DVB-T is transmitted as MPEG-2 format (essentially the same as DVD), or MPEG-4/H.264 for the high-def channels.

Recording DVB-T takes next to no CPU power at all.  Your DVB-T card quite literally just takes the incoming DVB-T stream and writes it to your disk. As you are not watching or changing the stream, there is no encode/decode process.  It's about as CPU intensive as copying files around on your machine.  "top" reports less than 1% CPU load when recording a show to disk on my AthlonXP 2400+ (2.0GHz) single-core machine.

I have my MythTV box set to transcode all recorded shows to Xvid after they are recorded.  This shrinks them considerably and saves disk space.  MythTV allows this to happen on low priority (ie: "nice -n 20") so that it doesn't interfere with other more "real-time" tasks like playback of media.  Only free CPU time is given to Xvid transcoding/compression and commercial flagging, so if the machine has other things to do (like decode other video for the viewer), those tasks come first.

With one card recording a TV show, another show being commercial flagged and transcoded in the background, I can still happily watch recorded media, DVDs etc on my machine without any skipping or playback issues.  Adding another card to the machine won't affect that very much at all.  I'd quite literally need to add dozens of cards before I saw any effect kick in, and even then it would probably be my hard disk that was too slow before my CPU complained about it.

The only thing my little AthlonXP can't do is decode (ie: playback) of realtime hi-def channels.  It tends to drop frames every 5 seconds or so.  But whenever I record hi-def channels (remembering again that recording them merely throws them at the disk, and doesn't do any encoding/decoding), I then transcode them in non-realitme AFTER they are recorded (and again, at low CPU priority), which also resizes the frames to a lower resolution, which then lets me watch "hi-def" shows (I use the quotes there because they are downscaled from their original hi-def resolutions, and are no longer truly hi-def).  Now that Channel 10 and others here in Australia are showing different content on their hi-def channels to their standard-def channels, it's nice to have the freedom to watch them without needing a hi-def TV nor fast computer to decode them.

And of course the single biggest plus of a MythTV box is the commercial skipping.  I can't stand TV at the best of times (I set all of the above up primarily for my wife), and TV ads in particular are enough to send me screaming from the room.  Having them auto-skip means I can stand to be in the same room as the TV (and thus my wife) for extended periods of time without being commanded to "BUY NOW LAST DAYS CLOSING DOWN SALE!!!11". :)

-Dan