Techie problem for Billyboy to solve?

organism_seven wrote on 5/27/2003, 6:36 PM
Hi,

I posted this problem/question previously, without receiving any responses.
This is really unusual for this forum.
Either I am asking about something very simple that I should really know the answer to, or its a problem that others have never experienced.
I'm curious to know which one it is.
Reading this forum regulary, I know that BillyBoy usually has ideas or solutions to a lot of the problems that arise. So, can I ask for your help/ideas?

The Problem:


Could anybody provide me with an answer to the following?

Do all camcorders (such as the Canon XM1 and other models with a similar spec) capture footage lower field first?

If not, why not? Surely this would keep things simpler.
Or is it just a difference that applies only to NTSC /PAL camcorders.

I ask because I am having some real problems converting some AVI files I have edited in Vegas, and I am now trying to convert them to MPEG2.
I have tried using the inbuilt Mainconcept codec and also TMPGEnc Plus.
Neither will work.

When I encode them to MPEG2 I keep getting the "jittery" look on my TV screen, as if I have encoded them with the wrong field order setting.

But it doesn't matter what setting I choose, lower, upper, or progressive the footage still plays back "with the jitters" (on the TV screen).

The original avi files play back fine, and I have played them and recorded them to VHS and the picture quality is perfectly OK (for VHS!). no jitters!

Now, this problem has now started me thinking.
If I right click on the avi files on the timeline in Vegas the properties tab tells me the footage is upper field. But I am sure that all footage captured with my Canon XM1 is lower field. I have checked previous footage and its all lower field.

In this latest file I have produced, I used three cameras.
My Canon XM1, a Sony Digital8, and a Sony Hi-8. (Don't ask!!).
If any of the other cameras capture footage upper field first, how the hell would I be able to encode a project using footage from both and convert to MPEG2?

If anyone can see what I am getting at here, I would appreciate a plain english explanation. Particulary, if you can find a solution to encoding this footage to MPEG2 without me getting the jitters!

Thanks.

Comments

kameronj wrote on 5/27/2003, 7:28 PM
You mention that the jitter comes on you television.

Do you get the jitter in vegas preview - or when playing the mpeg in a media player?

If no, then how are you playing on your television? Are you burning on a DVD or a VCD? You may want to look at that as the issue since this seems to be the only constant in the problem.
BillyBoy wrote on 5/27/2003, 7:29 PM
I remember asking Dennis or one of the other SoFo guys some time back if the settings under Properties override any difference with regard to field order in the source files. In others words should I mess with them, changing them to what my project is going to be? As I recall, the answer was no, don't change, the properties settings does override. So it shouldn't matter even if you do mix source files with some upper, lower, or progressive. Just set the properties to whatever you need. I believe lower field first is the default for DV. I've always used it regardless if making a DV or VCD SVCD as MPEG-1 or MPEG-2.

Just curious, when do you see the shakes?

On your external monitor AFTER you render to MPEG-2?

On your regular TV, if so played back from camera, VHS, burned DVD, what?

The only time I've somthing similar is after rendering a file with the MC encoder for some odd reason every 10 seconds or so there would be several vertical shaking for a second or so, then OK... repeating through the all rendered video. I assume you see something else. Any chance you can put up a few seconds of it so others can see?

SonyEPM wrote on 5/28/2003, 8:27 AM
First off, esp. in the case of MPEG-2, do not make any assumptions about field order when viewing your footage on a computer screen. Software playback is no substitute for burning to DVD and watching on a TV. That said...

If the source material used in Vegas has the correct field order settings (set in Media Properties), there should be no problem- you'll be able to mix footage from different cameras/sources.

In the case of DV, it'll always be lower first or progressive, depending on how you shot it. We sniff this info from the DV file and if you use our capture tool the field order should be correct unless there's some funkiness with the tape. The XM1 footage should not ever be auto-interpreted as upper first if you are capturing over 1394 with our capture app- if it is, that sounds like the problem, so switch to lower.

In the case of other video formats (Hi8 taped off of TV captured through an MJPEG card for example), you may need to change the field order source material to match the original. Vegas will make a reasonable assumption about the field order...but we can't always be right since we don't know anything about the original footage. Some trial and error may be required for non-DV originals.

Once all the footage has the correct field order inside Vegas, we do the right thing when rendering to the destination format and you shouldn't have to worry about it further.

Render settings override project properties of the same type, so if your project is set to say, progressive, and you render to lower first...the rendered file will be lower first.

mikkie wrote on 5/28/2003, 9:27 AM
Perhaps another way of saying the same thing FWIW...

An individual clip on the timeline has it's field properties, which may or may not need to be set - as it's only a rite click thing, *if you're unsure* doesn't take a moment to check & correct if nec..

The proj has it's properties. If the clip is different then the proj, the clip will be converted to the proj settings while editing, in the preview etc.

Render settings have the final word, so you could have a lower first clip, converted in an upper first proj, rendered to a lower first, giving you the same basic results as if your proj was set to lower first.

But whatever the case, wouldn't hurt to make sure your prob. is field order and not residing elsewhere.
organism_seven wrote on 5/28/2003, 7:33 PM
Hi,

Thanks for all the info, but I'm still not sure I can "cure" my problem.

Some more details as requested:

The footage is 4:3 DV PAL captured from my Canon XM1.
Rendered out from Vegas to AVI using the PAL DV template (which uses lower field first).
This AVI file plays perfectly outputted to my PAL TV using Windows Media Player 9.0. via my 1394 OHCI compliant firewire card.
The strange thing is, this footage is playing back on my computer screen as its outputting to the TV, and it looks as though it is rendered using the wrong field order!
So, this AVI file looks good on the TV screen, but bad on the computer screen.
I've seen this happen the other way round, but this is a new one on me.
This AVI has at least enabled me to make VHS tapes, but I'm screwed when trying to produce a DVD.

Now, when I convert this file to MPEG2 in Vegas using the standard MC DVD PAL template, the problem occurs the other way round!
I get the "jitters" on the TV, but it plays fine on the computer screen.
I have tried to play back both the AVI and the MPEG2 files in Windows Media Player
and PowerDVD. Both display the same symptoms.
As suggested, I thought I may be being fooled by using software players, so I burnt the MPEG2 to DVD using DVDA.
Tested it in my standalone DVD player and I got the jitters effect!

BTW, the footage is actually of a soccer match.
The problem becomes really bad when any fast motion occurs.

I would be happy to upload some small sample files to try and solve this mystery.
Where would I post these to?

I have imported new footage since this problem occured and everything is working fine.
I'm confused!!

Hope this extra info can shed some light!
Thanks.