I have PE 12 and only use it for editing my own Go Pro footage. I put together a short vid and was disappointed with the quality after rendering. From the searches I did on here is that I needed to start the project with the correct video quality identified. The GoPro shot it in 720P 30fps. I tried doing this on a short clip by starting a new project and set the video quality from the start and it worked, my quality after rendering is much better. So now I have this vid I created prior to knowing this and am hoping there is some way to change this setting to an existing project? Or do I need to start over and make sure those settings are right? That would suck, because I have several hours into it already and would hate to start over!
If you find that you did not use the best and/or correct project preset for your project after you established the project preset, the Adobe party line is that you start a new project.
But, I have found it is possible to change project settings in this situation under certain circumstances. The technique involves editing the Notepad document of the saved closed project. After weighing all factors, you may find it easier for you to start a new project. Please review the details of the technique, and then decide what is in your best interests.
But, I would ask "What is the project preset that you have, and to what do you want to change it?"
Be advised that the project preset set by you (manually) or the project (automatically) should match the properties of the source media. What you do with the export settings in another matter for further discussion.
Please review, consider, and then we can decide what next.