There are many reasons why your video looks soft. It may be the video output settings, or it may be the publish settings in Flash. Is your original artwork all done in Flash as vectors, or have you imported bitmap art from Photoshop?
What settings are you using to encode the video?
Also unless I'm wrong if the video is not playing the nested animation it might be because the symbols are movie clips. switch it to a graphics clip and they'll play on export.
the export settings in flash are as they are - there is not much choice. The stage is 800x480.
The artwork is all as vectors.
In Adobe Encoder is used the settings H264 HD 720 23.976.
The eye blinks are done with shape tweens.
When importing the SWT into After Effects I lose also the movieClips that are added to the stage during playback, with code.
They are in SWF. But when importing into AE, they are gone.
And also some movieClips that are moving along the stage with code, are standing still in AE.
If you change the size of the image or the aspect ratio or the frame rate from the Flash version to the video version, then you are going to be altering the image.
Well there's at least some of your trouble. You can NOT export a movie clip with code to a video. it won't work, which is probably WHY your movie is blank in the first place. Especially if you're asking that code to place movie clips onto the stage. Forgive me if I missed you explaining this in the beginning.
The way movie export works in Flash is almost like taking a screen capture sequence (although not exactly). But basically, what plays live in real time on the stage is what will export. SO, if you want to export your file as a video you'll have to place those movie clips on the stage yourself, set frame ranges for how long they need to play and then make sure the clips animate on the stage in real time. Personally we use Graphic symbols and NOT movie clips and I don't believe they export well to a video.
I changed the size of the stage to the expected size of the video and the outcome is acceptable.
Asymetrical - it is possible to export a video having it perform with code, not only with timeline. I did it. Using movie clips.
Maybe with graphic symbols the video would be even more crisp, but with this project it is to much work to do that change.
Just to add to the discussion, I author a lot of Flash animation for video format and I always start off with my Flash stage size set to 1920x1080 and export to this same dimension.