I am creating a 5min animation in AE that needs to be imported to Flash so some clickable web links can be added. My AE comp is 720 X 480. When I render it as a FLV to prepare it for Flash it gets squashed width-wise so that I must stretch it in Flash by W 110% to return it's shape. This unfortunately creates verticle wiggles when the SWF is published.
These FLV's have black bands on the right and left with the image squashed horizontally. I honestly don't know what could be doing this. I feel like I have done every combination of settings but maybe I am missing something. Compression isn't my strong suit.
Check your pixel aspect ratio on both your comp and export settings. Seeing 720 X 480 makes me think you're using NTSC with a pixel aspect ratio of .91 (slightly rectangular). You need to be setting this to square (may be listed as 1.0 or 1:1).