what's the best format to convert Mp4 to, for use in vegas8)
 

It's quite rare, but sometimes I need to use Mp4 (for example shot with my iPhone 4 in 720) (I use vegas 8.c) so they wouldn't work.

obviously when using the ex1 I can use the clip browser to transcode to mxf, but when I have other mp4s from other sources, what should I convert them to?
which tool should I use?

I have a GoPro camera that shoots MP4 files - they load just fine into Vegas Pro 9.

Edward is correct in that Pro 9 had fixes for the ongoing QuickTime issues that regularly plague any non-Mac users, Vegas included.
Some users found that rolling back to QuickTime 7.6.4 (or even earlier) resolved their issues but that doesn't seem to be the case with newer devices such as iPhones :(

yes I tried that route, problem is if you "downgrade" quicktime the latest Itunes doesn't work so : )

but my question was if I can trancode to another format my mp4 for use in Vegas 8, and if so which one you would use

the problem has been solved in Vegas 9 but I want to stick with 8c

If you need to transcode, you should use a near lossless file format such as Cineform. Cineform is an intermediate codec that is designed to not hurt the video quality. Delivery formats are inappropriate for intermediate transcoding for editing purposes. They create too many compression artifacts.

I have to do this all the time, I'm currently working on a clip where I have to use low quality portions of Youtube footage that is in low res MP4 and even FLV, the quality is hideous, I cant afford to make it any worse.
I have Cineform which I would normally use, but until I got that I would render to Lagarith and edit with that, you lose nothing, what you put out is as good as you got.
Lagarith is a bit harder on the timeline preview, you just have Ram preview alot if you have an older machine.

Cineform is the only one that's worked for me. All the others, like Avid or Matrox either give error messages or are stuttery in preview.

I think iTunes is so bad, it should be considered malware. I've used MP4's in all versions of Vegas with no problems. (well, the three I've used are Vegas 7, 8, 9). I have the K-lite codec pack installed, along with the "quicktime alternative" driver. That way I don't have to taint my computer with Apple software.

But, if you insist on converting the file, just pick one. AVI, MPG, it shouldn't really matter.

Most people also recommend against installing codec packs as well.

I guess I'm not "most people" hehe.

Generally speaking, it's best to only install the few specific codecs you need. By installing a codec pack, some people have literally been unable to load many formats they previously WERE able to load. They can definitely be problematic in some cases.

All I'm saying is - think twice before installing a codec pack and have a means of rolling back your system if it causes problems. And also be aware that some codec packs have included spyware in the past. This may not be the case today but also causes one to be leery.

Ever tryed TMPENG?
Works very very well

"All I'm saying is - think twice before installing a codec pack"

Right! And ffmpg killed the ability of my Camtasia to create flash files. Worse yet, it wouldn't uninstall - I had to rename some files that ffmpg had installed in order to kill it.