I have an issue where I cannot import MP4 files into Vegas in their entirety, only the audio shows up.
I took a good look at the MP4 files outputted by Action! using MediaInfo. If you look at it with this program, you'll see that under the heading "Muxing mode" in the video stream, it says that the profile is baseline and level 3.0. However, it also says earlier on that the profile is baseline and level 4.1. This is the same in both types of MP4s that Action! outputs (480p and QuickSync).
That's my guess as to why Vegas doesn't open the video stream. No other MP4 file made with the encoders I have (x264 and whatever Vegas's internal encoder is) has this attribute in their video stream entry. Wikipedia's article on H.264 says that the 3.0 level only supports standard def resolutions (it gives as an example a max res of 720×480@30.0fps).
I usually record at 60fps. If I turn the resolution down to 480p and the framerate down to 30, making it compliant to the 3.0 specs, what do ya know, the video stream appears in Vegas!
I can also get my 1080p/60fps recordings' video to show up in Vegas by demuxing the MP4 back to its elementary streams (using a program like YAMB), stripping that unnecessary piece of metadata in the process and remuxing it back into a working Vegas-perfect MP4.
You need to stop your MP4 muxer or encoder (not sure which) from writing this 3.0 level metadata to the file, apparently Vegas is quite strict about compliance to this standard!
EDIT: Apparently 1080p@60fps isn't compliant to level 4.1 either. And yet when remuxed without the 3.0 metadata it still imports to Vegas (edit the command line in YAMB by checking "View or Edit MP4Box Command Line" in the options, go to the mux tab and add "-fps 60" to the end of the command line). Strange! But still, the elementary streams in the MP4 files outputted by Action! need to be compliant to the standard specified by the level written in the header...
Here's a little before-and-after remuxing test footage so you can see for yourself what I'm talking about:
http://www.mediafire.com/?i382idr6awxrj ... d1f0p72m22