flictering lines at bottom of screen

Uniwoo wrote on 11/9/2006, 12:20 AM
I'm sure I've seen this here before, but I can't find it. I've rendered a couple of clips in mpeg and wmv and there are several flickering lines occupying the bottome the screen. What is causing this? BTW, I've not gotten so far as to play with interlacing and field order, could this be part of my problem?
Thanks!

Comments

PeterWright wrote on 11/9/2006, 12:45 AM
If the footage originated as VHS or similar analogue format, this is usual - it is not usually visble on TV screens, but shows on PC playback.

On the other hand, if the origin was DV or other digital, I'm not sure where the problem came from.
farss wrote on 11/9/2006, 12:59 AM
And if it did originate from an analogue source I'd suggest masking it and any other ragged edges out. In theory you will not see them on a TV, a PC or LCD /Plasma display possibly will reveal them. Either way if you're encoding to mpeg-2 they are using up bandwidth.
Grazie wrote on 11/9/2006, 1:11 AM
Noise is the enemy of MPEG! Learnt that from Bob! Flickering = Noise. Get rid.

I recently did a shortie. I had a flicker as a result of using some FX. It was right along the the top edge. Created a 2 or 3 pixel border. Re-rendered, zapped it thru Windows Encoder. Flicker gone. Windows Media Player don't even know its there now - it DID B4!
PeterWright wrote on 11/9/2006, 1:17 AM
Yes Bob - masking is much safer than cropping - I've tried a few "minimal" crops and it very often introduces artifacts/flickering.

I'm hoping to hear whether this is related to the cropping swapping the field order, and if so, how we can avoid such an outcome.
Grazie wrote on 11/9/2006, 1:44 AM
OK, Peter, I understand now.
PeterWright wrote on 11/9/2006, 2:07 AM
Grazie - I think your method of using Border FX is a great way of masking - it keeps the original frame resolution and "hides" the fizzy bits near the edges.
As I said, doing a slight crop causes a lot of rescaling, and often messes things up.
farss wrote on 11/9/2006, 2:30 AM
Problem with the border FX is it's symetric and you usually need to mask more at the bottom and LH sides. I use 4 extra tracks filled with gen media black and track motion to position them, that's how I can spend so much time posting here, waiting for the damn thing to render. Ah well Vegas has it's ups and downs, if it rendered too fast I'd never have time to talk to my mates.
Grazie wrote on 11/9/2006, 2:33 AM
Worked for me Bob. In fact you just saw the labors of my work, not less than 24 hours ago!! - Mates? You got mates? Huh, I don't .. . miserable Git that I am!
farss wrote on 11/9/2006, 2:41 AM
You were shooting DV, I was refering to what happens when you capture analogue, such as Hi8 or VHS.
Grazie wrote on 11/9/2006, 2:49 AM
Correct! . . slinks away, Golom-like .. tail between legs
farss wrote on 11/9/2006, 2:58 AM
In light of your Velcro post are you certain it's a 'tail'?