I have a LaTeX Beamer presentation that I output into a PDF slide show. I want to turn into a video file (with the ability to add sound later) so that I can generate animations from Beamer . How can one do this? I've tried importing the PDF to iMovie, but the quality of the frames drops dramatically.
Convert the presentation to a series of image files. The classic image format for that is a TARGA sequence. But you can use any format that your LaTeX tool chain can output and a video generator can import. For generating the image sequence, there are several vector and raster formats that LaTeX can export. You can then use ffmpeg to turn the image sequence into video.
As a reminder, be sure to set the aspect ratio of your presentation appropriately.
You could convert the PDF file to PNGs (use density 144 for double the size):
convert -density 72 in.pdf out-%04d.jpg
Then import the images in any decent video editor, add a sound track, fine tune the result and export/render the video.