Bjørn H Jespersen of the excellent .processing blog assisted greatly in identifying this as a BETAB-500M62 free-fall 500kg bomb, primarily used to attack concrete and hardened structures, as seen here [source]
According to Jane's the "bombs are believed to be cleared for carriage on MiG-21 'Fishbed', MiG-27 'Flogger', MiG-29 'Fulcrum', Su-22 'Fitter', Su-24 'Fencer', Su-25 'Frogfoot', Su-27 'Flanker', Tu-95 'Bear', Tu-16 'Badger', Tu-22 'Blinder' and Tu-22M 'Backfire'", which includes the aircraft used by the Syrian Air Force.
Update September 19th The second half of this video shows the same BETAB as filmed above
Evidence Of Cluster Bombs Being Deployed In Syria
New Cluster Bomb Evidence Emerges From Syria
A Beginner's Guide To Identifying UXO In Syria
The Mystery Of The Syrian Barrel Bombs
You can contact the author on Twitter @brown_moses or by email at email@example.com