DVD vs TV same decoder

[phantomfsoc]

I know this has talked about for ages, and I've read alot on the subject but.......

I was just watching a DVD using MCE. I was paying attenion to the pic quality because I had just finished playing around with my Nvidia decoder settings.

My question is, why is it that watching TV through Sage always has problems with pic quality like motion blur, colors, studdering and more, but using the same decoder to watch a DVD never has the same issues.

I know that its something to do with interlacing but I just can't seem to sink it in.

WHY WHY WHY

Anyone wanna explain it simply for the 7423rd time???

[kny3twalker]

simple fact that DVD are nicely flagged for deinterlacing
and TV is not
also the fact that our encoders in the pvr cards are cheap

the networks do a much better job of encoding the shows, than our pvr cards can

[stanger89]

And because DVDs are encoded by multi-thousand (million?) dollar offline encoders, and their free to go back and re-encode sections that come out poorly.

Oh, and those encoders have access to more than about a half second of video at a time.

[Cayars]

yea, they have access to the whole movie at a time.

[kny3twalker]

the networks do a much better job of encoding the shows, than our pvr cards can

sorry was thinking about DTV/digital cable/satellite
which are encoded on the fly, correct?

[nielm]

Originally Posted by phantomfsoc

I know that its something to do with interlacing but I just can't seem to sink it in.

These 2 links should cover most of the problems
http://www.hometheaterhifi.com/volum...e-10-2000.html
http://www.100fps.com

Broadcast TV is interlaced -- you get 60 half-frames per second each showing slightly different pictures... This has to be de-interlaced and scaled to display onto the windows desktop (and then re-interlaced and scaled again if you use TV-out!)

DVDs are cleaner because (in general) DVD movies are not interlaced, so each DVD frame is a 480/576 line progressive frame, so you get no deinterlacing/scaling artifacts...

In NTSC land, there is a third problem with movies broadcast over the air -- they have to convert a 24fps movie to a 60fps TV signal, which means sending duplicate frames (known as 3-2 pulldown or telecine), which means that 4 movie frames are spread over 10 TV fields, which are then interlaced...

These factors mean that it is easy to decode a DVD, scale it and display it with no artifacts, but difficult to do the same for TV signals

(other issues have already been mentioned: quality of the MPEG2 encoder, quality of the TV signal, and that DVDs often are manually encoded -- with humans telling the encoder where the scene changes are to make sure that it can optimise the encoding to take this into account.)