"I have some DNxHD files with a .mxf extension on them which I would like to bring into After Effects. I've never done this before. I also notice that the audio left and right are separate channels. But I don't even care about the audio, I just want to bring in the video. How would you do this?"
After Effects does support mxf import/export, but only for a several codecs (which are pretty much acquisition/camera codecs). I've confirmed that. MXF import is basically limited to P2 and XDCAM. The easiest way to get at this media is to export the MXF from your Avid as a Quicktime, using the "Same as Source" option. In AE, you can render directly to DNxHD in a Quicktime container for fast-import back into Avid. However, it will be long-time duration for encoding the DNxHD MXF to Quicktime.
Luckily, there's an easier and quicker way to import Avid DNxHD .mxf files into After Effects. To do that, what you need is just a common video converter like EaseFab Video Converter for Mac, which can help you transcode DNxHD .mxf files to After Effects editing-friendly MPEG-2 codec with fast speed and zero quality loss. Besides, the program can also do batch conversion from MXF, AVI, AVCHD, MTS, MKV, MOV and more to seamlessly fit Final Cut Pro, iMovie, Adobe Premiere, Avid, etc. If you're a Windows PC user, you can turn to the Windows version here. Now download the right version and follow the steps below to start converting Avid DNxHD .mxf to MPEG-2 for After Effects.
Simple steps to import Avid DNxHD .mxf files into After Effects
Step 1. Load source video files
This program offers you two doable ways to upload your Avid DNxHD .mxf files, You can either click the "Add Video" button to browse your hard disk or local directories and load the target files or simply drag your local videos onto the interface. (Note: batch conversion is supported, so you can load more than one file to save time.)
Step 2. Select output format
Click "Profile" pull down list to select "Vegas/Premiere (MPEG-2)". The output video could keep the original quality of DNxHD .mxf files and seamlessly fit After Effects CC, CS6, CS5.5, CS5, CS4, etc.
Step 3. Start the conversion
Finally, simply hig the big Convert button to start converting DNxHD MXF to Adobe After Effects CC/CS 6 friendly video formats.
Within several minutes, you can find the converted file on your computer by clicking the "Open" button. And then you can import the converted files to Adobe After Effects easily.