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Aliasing when I compress .flv with deinterlacing

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Eric Olson
Aliasing when I compress .flv with deinterlacing
on Nov 7, 2009 at 2:48:02 am

I am trying to compress a 16:9 video out of Avid into an .flv. I have read that you should deinterlace your video for the web, but when I do this it actually CREATES interlacing problems.

Anyone have any idea what is going on here?

Here are specs on the source video:

-exported from Avid
-853x480 sq px
-Lower Field First
-29.97 fps

I then encoded in On2Flix at the following settings:

-deinterlace
-682x384 px
-29.97 fps
-2-pass,VBR,max bit rate 800 kbps

Don't seem to have this problem unless I deinterlace. Is it absolutely necessary?

Thanks,

Eric

P.S. Would have provided a pic but my computer is doing weird things with my screenshots.



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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 7, 2009 at 7:16:43 pm

Was the source video shot progressive?

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 12:15:10 am

Yes, the original footage is progressive as it was created in After Effects. The footage looked bad in the Avid window but the QT movie export looked fine.

EO


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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 9:50:52 am

I think you just answered your own question! No point interlacing/deinterlacing progressive material.

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 4:13:13 pm

Yeah, but it doesn't really solve my problem.


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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 5:01:25 pm

OK, a few things:

1. Your Avid project should be set to progressive and you export from there as progressive.

2. The frame size you are exporting at is not correct, each side should be equally divisible and ideally by 16 or by 8, so 856x480 would be much better.

3. The same applies to your Flix encode, a frame size of 688x384 would be ideal.

There's not really much else you can do. The bottom line is that you have imported progressive material into an interlaced avid project, exported it as LFF interlaced and then you are trying to deinterlace it, of course you are going to see problems!




__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 5:13:53 pm

I see your point about bringing the footage into a progressive Avid project. In this case, that would have worked because it is a purely animation project. And I'll do that with similar projects in the future.

However, I also have projects that are a combination of DV footage and AE footage. When you import into Avid it asks the field order of your project and non-interlaced is an option. It should then apply the correct field order to the AE footage on import and from there on out it should be treated no differently than the DV footage. Yes/no?

Thanks,

Eric


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 5:22:25 pm

I understand your point about the divisible by 16 thing. Although I don't think it would matter on export as I'm using the Animation (lossless) codec but would be important for the flash encoding.

http://www.flashsupport.com/books/fvst/files/tools/video_sizes.html

Man, could they make this stuff anymore complicated!!! You have to be a broadcast engineer these days just to get your stuff on the web and looking good.

EO


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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 6:43:40 pm

Div 16 is important but not as important as using even numbers, which all codecs need in order to work properly.

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 7:23:49 pm

[Eric Olson] "However, I also have projects that are a combination of DV footage and AE footage"

In those cases, render out of AE as interlaced.



__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 10:36:17 pm

Ok, the plot thickens.

1) I create an AE project 720x480 and 24fps, D1/DV PAR

2)I animate a line drawing and export QT with same settings using Animation codec. The QT looks great at this point.

3)I import to Avid Project at 24p NTSC, import settings RGB, 601 non-square, Ignore Alpha. At this point the video looks pixelated in Avid monitor window (don't have my CRT monitor hooked up as I'm running a minimal set up right now)

4)Add clip to timeline and export as QT, 24 fps, Animation Codec, 640x480 sq px

...essentially, I brought it into Avid and exported at exactly the same setting, aside from converting from D1/DV PAR to square pixels.

The pixelated result can be seen in the image below, even though the QT looked great coming out of AE. Essentially, there is no interlacing going on in this process at all and yet I'm getting interlacing effects.

Anyone have an idea of what is going on here?











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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 10:45:17 pm

It's easy to blame the Avid but there you have it.

Try an AE project at 640x480 square pixel and see if you get the same result.

p.s. what avid system are you using?

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 11:06:16 pm

I run Avid Xpress Pro 4.6

I imported 640x480 using "maintain square" then exported with the same setting as before. Didn't seem to remedy the situation:



Thanks for your help.


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 11:44:29 pm

Problem appears to be with export compression/encoding because when I render out as QT Ref the file looks fine.

EO


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Daniel Low
Re: Aliasing when I compress .flv with deinterlacing
on Nov 8, 2009 at 11:51:16 pm

QT ref just uses the same settings as you have in the Avid sequence. Flix is far from the greatest encoder. Do you have access to anything else?

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."
Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"
Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Eric Olson
Re: Aliasing when I compress .flv with deinterlacing
on Nov 9, 2009 at 12:02:31 am

I just realized that the version of QT I'm using is not compatible with Avid Xpress Pro 4.6. Need to reinstall 6.5.1 and see if that fixes the other issue first. Then I'll try to reencode.

EO


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