I can't think of any way to do what you want here. You may have to renest the new original into the new multicam, and recut the piece.
Alright, you feeling lucky, punk? Make a backup of your project file before you try this... and I make no guarantees that this will work, though in my brief testing, it did.
Open up your project file in a text editor; I like Notepad++. Premiere Pro project files are nothing more than XML documents, so we can decipher some of it and tweak it to make it do what we want. What I list below is, first, the line you're searching for, and second, the line you want to replace it with.
Here we go...
<PixelAspectRatio>1920,1440</PixelAspectRatio> <PixelAspectRatio>1,1</PixelAspectRatio> <FrameRect>0,0,960,720</FrameRect> <FrameRect>0,0,1280,720</FrameRect> <MZ.Sequence.PreviewFrameSizeWidth>960</MZ.Sequence.PreviewFrameSizeWidth> <MZ.Sequence.PreviewFrameSizeWidth>1280</MZ.Sequence.PreviewFrameSizeWidth> <MZ.Sequence.PreviewRenderingClassID>1345473880</MZ.Sequence.PreviewRenderingClassID> <MZ.Sequence.PreviewRenderingClassID>1297106761</MZ.Sequence.PreviewRenderingClassID> <MZ.Sequence.PreviewRenderingPresetCodec>1685483063</MZ.Sequence.PreviewRenderingPresetCodec> <MZ.Sequence.PreviewRenderingPresetCodec>1297107278</MZ.Sequence.PreviewRenderingPresetCodec> <MZ.Sequence.PreviewRenderingPresetPath>EncoderPresets\SequencePreview\079a6181-acbf-4a6f-b1f2-fb44555a69e0\P2 720p 60Hz DVCPROHD.epr</MZ.Sequence.PreviewRenderingPresetPath> <MZ.Sequence.PreviewRenderingPresetPath>EncoderPresets\SequencePreview\cf2f7860-0e56-444f-a64f-74eafec54e44\I-Frame Only MPEG.epr</MZ.Sequence.PreviewRenderingPresetPath> <MZ.Sequence.EditingModeGUID>079a6181-acbf-4a6f-b1f2-fb44555a69e0</MZ.Sequence.EditingModeGUID> <MZ.Sequence.EditingModeGUID>cf2f7860-0e56-444f-a64f-74eafec54e44</MZ.Sequence.EditingModeGUID>
That should do it. Again, just search for the first string in each group, and replace it with the second; you can do this en masse if you really haven't done anything else other than edit the multicam. What this should be doing is changing the frame size of the sequence (the first two items), since DVCPRO HD is anamorphic and AVC-Intra is full-raster, and then the last items are reconfiguring the editing mode and preview codec. This is a fairly simple change, since you're sticking with the same frame rate--that would be way more complicated and probably break the project file. I believe this will work, however.
If it does work... I like dark beers
Wow, Colin, yet again you come through with the answer to my problem! Worked like a charm. I'm encoding as we speak with the correct sequence settings all around. Thanks again for the fast, detailed response! If we lived in the same town, I would hand deliver a case of dark beer to your doorstep at 8am!
Sweet! Glad that worked! I had done just a little test converting nothing but a sequence (nothing in it) and it seemed to work fine, so I was hopeful but apprehensive. I've hacked into the XML a few times before, but never for something like this--nice to know it's an option.
If nothing else, this points to the desperate need we have to be able to change sequences after they're created in Premiere Pro. A feature request would help keep the fire burning: Adobe Feature Request/Bug Report Form
Good luck with the project!
As I was walking to work, I was thinking the same thing about making a feature request. If the change can be made by editing the XML file, then why can't it also be made via the sequence settings menu within Premiere? As you mentioned, a framerate change might cause bigger issues, but why does Adobe have to protect us from screwing up our project by graying out certian sequence settings that they don't want us to change? There are plenty of other ways Adobe allows me to screw up my project, why not just add one more method!
Colin, DM me your mailing address and t-shirt size. Since you're so helpful to all of us on these forums, and bailed me out of a few problem situations, I want to send you a Harvard shirt (my employer).