Proper use of Media Source Options ?

williege · Post by **williege** » Sat Sep 10, 2005 5:49 am

OK..... In MSP7, I've got two clips with the same bitrate and framesize. However one is interlaced upper field first and the other is lower field first. The project is set for lower field first. Under the Media Source Options for the first clip (upper first), do I want to set the Frame Type to Upper Field First? What exactly do I gain? When does it make sense to use this setting? Thanks.

Gorf · Post by **Gorf** » Sat Sep 10, 2005 12:58 pm

If you specify the correct field order for the first clip, you will lose the flicker when you apply filters and transitions, and the slight flicker at jump cuts.

williege · Post by **williege** » Sat Sep 10, 2005 6:04 pm

Thanks for the response. But let me ask for a clarification. When I render the video, it will be rendered lower field first (because of the frame settings in the options dialog). This means the first clip will be re-rendered and the second clip already matches so it will not be rendered again. My question is.... does MSP7 do something different with that first clip if I tell it ahead of time (via Media Source Options) that the source is upper field first? Or can I ignore that setting since it's going to rendered again anyway?
My initial eyeball testing doesn't show a difference in the finished video clip.

Gorf · Post by **Gorf** » Sat Sep 10, 2005 8:12 pm

williege wrote:...When I render the video, it will be rendered lower field first (because of the frame settings in the options dialog)...

MSP is completely ignorant about the field order of a video - it relies on you to know the field order. This may have changed with V7 or the latest version, but I don't think so.

If you put a lower field first (LFF) video onto the timeline, but you tell MSP that it's UFF in media source options, and the project is UFF, and you render to a UFF file - then the rendered file will be unchanged. As far as MSP is concerned, nothing has changed (with regard to field order). The fact that the field order was wrong throughout is irrelevant - it was consistently wrong, so the outgoing file had an unchanged field order.

There are plenty of operations that rely on the field order being correct. Even a straight cut will exhibit two-fields worth of jitter (that might not be noticed by most people) if the field order is wrong.

williege · Post by **williege** » Sat Sep 10, 2005 10:24 pm

When I put a UFF clip on the timeline, then render to a LFF file, it re-renders the clip regardless of whether I've selected upper or lower in the Media Options for that clip. MSP7 seems to recognize it for what it is, regardless of what I tell it.
Here's my situation. I have old VHS home movies captured on an ATI card that are UFF. I have newer DV (converted to MPG) home movies that are LFF. I want to include both in a video. Whichever way I try to render (upper or lower), the other clip suffers some quality loss, due to the frame change.
Is it possible to have a video clip that is partially upper, partially lower field first? If not, are there any suggestions on the best way to combine the two sources? Thanks.

Bill

Gorf · Post by **Gorf** » Sun Sep 11, 2005 9:49 am

williege wrote:When I put a UFF clip on the timeline, then render to a LFF file, it re-renders the clip regardless of whether I've selected upper or lower in the Media Options for that clip. MSP7 seems to recognize it for what it is, regardless of what I tell it.
Here's my situation. I have old VHS home movies captured on an ATI card that are UFF. I have newer DV (converted to MPG) home movies that are LFF. I want to include both in a video. Whichever way I try to render (upper or lower), the other clip suffers some quality loss, due to the frame change.
Is it possible to have a video clip that is partially upper, partially lower field first? If not, are there any suggestions on the best way to combine the two sources? Thanks.

Bill

If you put a UFF file on the timeline, and go to Media Source Options for the clip and chenge it to the (incorrect) LFF setting, then render a LFF file, it will not render.

What you have done in your example is tell MSP that the field order needs changing.

What I was suggesting was not what you should do - I was merely trying to explain the circumstances under which field order specifications result in no render. If I read correctly, in your situation, you have no choice but to change the field order at some point.

Changing the field order will not, in itself, produce any quality loss. That comes from the re-render. If you produce a finished file that is uncompressed, that file will maintain the video quality. I'm 99% certain you will need to compress it at some point, though, so it's best to do it from the timeline or use an external transcoder on your uncompressed edit.

williege · Post by **williege** » Sun Sep 11, 2005 9:05 pm

Thanks for your time and patience. Unfortunately I left out the fact that I was dealing with MPG2 clips, which is what caused my confusion. AVI's respond just as you say. You've been very helpful. I store the old home movies as Mpegs. I'll likely just allow them to be rendered as necessary to work with the newer movies.

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