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Field-based video to the web
Field-based video to the web
by kfredericks on Sep 19, 2005 at 7:24:17 pm

I have a three-minute AE video comprised of photo animations and MiniDV field-based video (720x480x29.97fps). I will output this to DVD with fields, which will keep the animation at 60fps and render the video in its original interlaced form. BUT, when I output this for the web, I'm a little confused as the proper way to render the best quality.

I hope to output a 640x480x29.97 version. So I have a few questions:

1) Should I use the render que stretch feature to get the 640x480 aspect ratio, or should I create a square pixel 640x480 composition and then drop my current composition into that?

2) If I shut off field rendering, AE will throw away half my video fields, right? Is this a fact of life, or is there some easy way of blending the fields that doesn't require interpretting footage or setting field blending for each clip. Keep in mind that i don't want to screw up anything with my DVD composition

3) For my DVD, rendering fields provides a high field rate for my animations, making everything smooth. On the web, my animations will be rendered at half the rate. Is there any way to render a 59.fps version without compromising the interlaced video content. I suspect that making a new comp set at 59.94fps would break my video content into fields, thus halving the resolution. If I did this, would it be optimal to render at 320x240x59.94fps so that my interlaced and non-interlaced content matches in native resolution? I know that is confusing, but I'm sure someone here with get what I'm saying.

I've read the tutorials on this subject, yet I am still confused. Surely there must be some basic rule of thumb for dealing with my scenerio above. All the various deinterlacing features in Premiere and AE confuse me.

Thanks in advance.


Re: Field-based video to the web
by Barend Onneweer on Sep 19, 2005 at 8:40:24 pm

I would just output one with fields, and another with fields set to 'none' in the output settings.

It generally looks good enough, especially since you're going to be compressing for web anyway.

If you're very paranoid about losing vertical resolution, take your rendered interlaced clip and use Magic Bullet or Twixtor to de-interlace it.

Bar3nd

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Re: Field-based video to the web
by Roland R. Kahlenberg on Sep 20, 2005 at 2:18:11 am

Barend's got a great article here at the COW that covers interlacing with AE.

As for your Qs:
1)Either way is fine since you're not rendering to fields. Stretching in the Output Module may create field mush IF you render out with fields.

2)Your footage, when interpreted correctly would have its fields merged to create a frame in AE. So effectively, you are rendering out from AE, not the original interlaced footage. And AE will be looking at the frames. You don't lose any pixel resolution but you will lose some motion smoothness going from 29.97 interlaced to 29.97 progressive.

3)Asking any computer to playback 59.94fps in realtime may be a bit too much to ask for. The fact that it is destined for the Web only compounds the issue. There's always a compromise between quality and efficiency when delivering movies for the Web.

In fact, you may want to look at a lower frame rate than 29.97 for your Web movie. Try 18fps. That will lower the bandwidth requirements; making your movie more accesible to viewers.

HTH
Roland Kahlenberg
broadcastGEMs
customizable animated backdrops with Adoeb After Effects project files


Re: Field-based video to the web
by kfredericks on Sep 20, 2005 at 1:53:50 pm

First let me say 'thank you' - thank you. Now for my follow-up to your responses:

"Either way is fine since you're not rendering to fields"
So effectively there is no difference between using the stretch feature or dropping my composition into another composition with a different frame size. Good to know. I'll use the stretch feature since it is easier.

"Your footage, when interpreted correctly would have its fields merged to create a frame in AE"
So AE doesn't simply throw away fields? It interpolates full frames from both fields automatically as part of the rendering process? The reason I was questioning this was because at one point I accidentally rendered out footage for a DVD WITHOUT fields. All video looked really low resolution. After redoing it, with fields, it looked a lot better. That is why I assumed AE throws away fields completely. It is however possible that while encoding to MPEG2 (in encore), it reinterlaced the deinterlaced footage, resulting in a two-step degrading of video, giving the effect I experienced.


"Asking any computer to playback 59.94fps in realtime may be a bit too much to ask for"
Yeah, I agree. I was just asking for education purposes as much as for practice. Ultimately though, I will be posting this video in high-quality form, as I think it deserves to be seen that way. I think it is prudent though to also include a lower-bandwidth version in addition to the high one. I'll shoot for 320x240x30fps with liberal compression. As you know, finding a balance between quality and file size is an artform in itself.

Thanks again. And any more insights in this arena are appreciated.




Re: Field-based video to the web
by Roland R. Kahlenberg on Sep 20, 2005 at 2:31:21 pm

[kfredericks] "So AE doesn't simply throw away fields? It interpolates full frames from both fields automatically as part of the rendering process? The reason I was questioning this was because at one point I accidentally rendered out footage for a DVD WITHOUT fields. All video looked really low resolution."

AE doesn't throw away resolution unless you ask it to. ;-) If footage interpretation, work within comps, and render settings are set correctly, you shouldn't lose resolution going from an interlaced footage to one that is progressive.

Then again, what is resolution? What were the artefacts you experienced?

[kfredericks] "I'll shoot for 320x240x30fps with liberal compression"

Viewer experience is what you should be aiming for - and that involves not only frame rate but also visual quality. Going for 30fps at the expense of visual quality, "liberal compression" is a walk along a tight-rope exercise that you may want to forego.

I'd suggest going for a lower framerate. Perhaps 18fps and upping the quality slider. If you have the time to experiment, I suggest that you experiment with both, or more settings.

At the end of the day, it depends on the CODEC that you choose. I suggest that you visit the COW's Compression Forum for advice on a CODEC to suit your needs.

Cheers
Roland Kahlenberg
broadcastGEMs
customizable animated baackdrops with Adobe After Effects project files










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