I posted a related topic some weeks ago. I have been using mocha and mocha import+ in order to track squares from a video so I can put pictures inside. Well, the pictures follow the movement correctly, both when there is need for corner pin and when there isn't. My problem comes when I track with perspective.
Once I import the txt Mocha creates (using the Mocha Import+ script), the picture gets deformed. I don't understand where I am making the mistake, if when I am tracking on Mocha or when I am importing to After Effects.
I have seen lots of tutorials, which have been useful to get to understand the program, but I am yet to find one that explains this.
The most common mistake here is that your insert later is not the same size as your comp. Make sure the insert is same size and if not, precomp it. The true test is to simply apply tracking data to a solid that is the comps size. If this does not lineup, than your issue is with the actual track.
also, mocha Import+ is not "necessary" for doing screen inserts. The track data can simply be applied to a layer. What mochaImport is useful for is to stabilize a comp, insert elements or do a fix and then remove the stabilization.
In general I would start by learning the workflow for applying a corner pin to a solid to make sure you understand the general workflow.
There are very many excellent tutorials on mochaImport found on Mamoworld's site.
Well, it has taken me a long while, but I have finally understood the problem.
When I read that the picture to be implemented had to be on a pre comp with the same settings as the original, I was adding a 1920x1080 pre comp into the 1920x1080 original comp, resizing the pre comp as I saw fit. My mistake was the following:
The squares where I wanted to put my pre comp had a different size: 238x351 originally, but I have worked with 1190x1755 (238*5x351*5).
So, while my original composition was 1920x1080, the squares inside the frame I recorded were 238x351, and this is where I wanted to corner pin the photos. Now it its working perfectly, and it is understandable that a 1920x1080 pre comp was deformed when being put into a frame sized at 1190x1755.
Oh, the headaches I could have spared if I had understood this from the beginning… :o(