You may expect the 4K support in Avid, since it seems like everything is shooting 4K these days. Although Media Composer has already had 4K support via Avid Media Access (AMA), there's actually no way to edit a 4K project natively with Avid even the latest Media Composer 8. In most cases, editing 4K in Avid Media Composer is very taxing on your computer. To import 4K MXF/MOV/MP4 into Avid Media Composer flawlessly, an ultimate solution we found would be to transcode/compress 4K to DNxHD for Avid Media Composer.
As mentioned above, Avid Media Composer lacks native support for 4K video. What’s more, there are so many 4K source in different video formats- MOV, MP4, MXF like from Panasonic GH4, GoPro Hero4, Sony FDR-AX1, Sony PXW-X70 and more. However, format compatibility issue is quite common in the video world, which is also true to the stunning 4K. If you're planning to edit 4K in Avid Media Composer, just read on to find something you need.
To prepare 4K footage for Avid, the easy option is to convert 4K MP4/MOV/MXF to Avid Media Composer supported DNxHD in 1080p settings. Brorsoft Video Converter for Mac is a professional tool that can deal with 4K videos regardless in .MP4, .MXF, .MOV format to DNxHD for Avid Media Composer editing without quality loss. It also enables you to customize the output resolutions to any size like 1080p, 2K, 4K as you need. Besides Avid, this 4K video converter can also encode/re-encode 4K files for smoothly importing and editing in Adobe Premiere Pro, Final Cut Pro, iMovie, Final Cut Express and more non-linear editing systems (NLE). For Windows users, you can turn to Video Converter.
Now just download the program and follow the below guide to convert 4K MXF/MOV/MP4 for playing and editing in Avid Media Composer perfectly.
Step 1: Load 4K videos
Run the best 4K Video Converter Mac and load 4K MP4, MOV, MXF clips to it by clicking “Add” button. You can also drag and drop the 4K files to the software directly from your Hard drive.

Step 2: Choose Avid compatible format
To encode 4K files to Avid Media Composer, choose Avid Media Composer -> Avid DNxHD (*.mov) as the target format.

Tip: You can click "Settings" to fix the frame rate, bitrate, video size, etc to your needs, that you can play and edit 4K movies in Avid easily. Generally, 1080p video size is good for Avid MC editing.
Step 3: Convert 4K to Avid Media Composer
Click the convert button under the preview window, this 4K to Avid converter will start encoding 4K video for Avid Media Composer.
After the conversion, click the “Open” button to locate converted files, and then you can load the converted 4K MXF/MP4/MOV files into Avid Media Composer 5/6/7/8 for editing smoothly with the best quality.
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Source: Transcode 4K MXF/MOV/MP4 to DNxHD for Avid MC