Output H.264 Video From After Effects
If like me, you have come across error messages when trying to render out H.264 video from your Render Queue in After Effects, there is a solution…
Add your composition to the Render Queue as usual, and go to the Output Module: Lossless setting.

Output Module
The Format defaults to QuickTime Movie, but click on the Format Options… button.

Format Options Button
When the next panel opens, select H.264 as the compression type.

Compression Type
Ignore the warnings and render your video.
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THANK YOU!!!!!! YOU SAVED MY LIFE TONIGHT!!!!!! *BLESS U DUDE*
You are welcome Natalie.
Mine still craps out on me all the time. rendering from iphone video.
Try using QuickTime and see if that is better for you.