[FFmpeg-user] Blocky flash video - how to fix

[Joe Blo]

Hi 
I have a flash1 video (Sorenson Spark) 15 frames / second. Its a video of a professor writing with chalk formulas onto a blackboard (green). Unfortunaly since the video exhibits blockiness it is impossiblle to read the formulas written to the blackboard (greenboard). Is there any chance to fix this imperfection with conversion, interpolation, sharpening, postprocessing in ffmepg/ffplay. I have used VLC to play the media. 
Interestingly comparable material (same flash1 but with 5 fps recorded)  displays very fine (readable formulas on blackboard(green)..  
Please help if you have any ideas what I could try to fix this problem
Thanks