Bad Interlacing
by Benny B
on
Oct 7, 2007 at 7:39:35 pm
Hi,
I have just rendered a DVD project, DV source files from two different cams.
Some footage, say from cam_1 is widescreen PAL 720x576(pixel AR 1.422), cam_2 however is reencoded DV footage from DVD (vob's), actually it has been streamed from that DVD through VirtualDub Mod and saved as avis (Panasonic DV codec) aspect ratio for cam_2 footage is (720x526 with pixel AR 1.067) it is also PAL. Originally cam_2 footage was also DV (couldnt get DV format)
Both files are interlaced
Now, Sony Vegas Project is 1.4568 (PAL DV Widescreen) interlaced,
cam_2 footage was cropped to mach project AR (top and bottom parts were cropped out)
The rendered mpg has now very bad interlaced artifacts, I mean VERY, when played back on TV or PC. Only takes with cam_2 footage are affected. Takes from cam_1 are OK.
I checked whether this is caused by cropping of original footage and indeed that seems to be the reason for that unwanted 'effect'
The big Q is if there is any way to reduce interlacing
Need to add that i tried almost every possible switch in Sony Vegas but this has not worked for me.
Any ideas?
Am I missing something?
Help much appreciated
Re: Bad Interlacing by Mike Kujbida on Oct 7, 2007 at 8:54:40 pm
Sounds to me like your cropping on cam 2's footage changed it from lower field to upper field.
Try cropping it again but this time shift the crop position one line lower or higher.
BTW, why would you bother with VirtualDub Mod when Vegas can import DVD footage?
You could then do your cropping right in Vegas.
Re: Bad Interlacing by Rick Mac on Oct 7, 2007 at 10:57:20 pm
[Mike Kujbida]"Sounds to me like your cropping on cam 2's footage changed it from lower field to upper field.
Try cropping it again but this time shift the crop position one line lower or higher."
I agree with Mike. Seen this happen before and as Mike suggested moving the the crop position up or down one line can fix it.
Regards, Rick
Rick Mac
Director of Audio Production
TCT Network - Directv 377
Re: Bad Interlacing by Benny B on Oct 8, 2007 at 5:58:07 pm
Mike, Rick
Nope, no luck here, moving cropped image dosent seem to work out
The only thing which might have been missed out is fact that DVD footage GSpot reports VOBs as 'top filed first', wheras VirtualDub apparently changed the field order during capturing to bottom field first but that is consistent with my project settings
Re: Bad Interlacing by Mike Kujbida on Oct 9, 2007 at 12:22:32 pm
The reason for me not using Vegas for DVD capturing was HDD space, I needed only couple of takes from that DVD, probably my mistake, who knew?
Benny, as long as this is not a copyrighted disc, try using DVD Shrink (Google for it) to extract the relevant section.
I seem to recall someone saying that it can do this.
Re: Bad Interlacing by Benny B on Oct 9, 2007 at 7:44:06 pm
Hello again,
First many thanks for your input and valuable tips,
I think I have learnt a lesson recently,
-first: NEVER resize interlaced video footage, unless you know what you are doing
-second: first think then do
The only excuse which I have is that I am newbie in video editing and still learning, that lesson will remember forever
What I should have done in order to avoid all this:
1.go for 4:3 project settings -not much an option, +90% of the footage was anamorphic widescreen
2.do not crop at all- well, two vertical bars on both side of screen is not much eye appealing, is it?
3.use other capturing method -however the way I acquired DVD files is also good as long as you are dealing with progressive scan material or the footage is not reencoded the way I did (DVDs vobs to avis using DV codec)
I have noticed that the way Vegas process different video formats vary quite a lot. Mpeg video files (interlaced) are first de-interlaced than cropped/edited etc and then re-interlaced
DV avi files are on the other hand never de-interlaced prior to editing/cropping, thus any vertical crop results with "double interlacing" making output quality-wise intolerable creating sort of 'interlacing interference effect'
Another unwanted 'feature' seems to be that Vegas first crops the frame and then stretches out to fill the frame, In my opinion that should be all the way around ie first upscale the whole frame so it matches crop aspect ratio then interpolate missing lines and finally crop
How to fix when it already too late ie your movie is already on the timeline? thats my formula:
-the bad interlacing effect can be mitigated by changing the media properties to progressive scan (right click>media properties>change field order) that improved final output a lot, need to say the interlacing artifacts are still visible but now are tolerable
