Those sequences were all encoded from the same source using the M$ WMV9 VCM Codec (with a VfW interface) to the AVI file format (no audio). Using that encoder, first frame seems to be always corrupt. Under some circonstances, I managed to have 2 consecutive keyframes, therefore allowing to trim those frames. The binary codec is available here: http://www.microsoft.com/windows/windowsmedia/9series/codecs/vcm.aspx => http://go.microsoft.com/fwlink/?LinkId=33853 The sequences have those properties: - presumable no B frames - Encoding at those quality levels (therefore constant quantizer expected): 60% (q60), 80% (q80 and 94% (q94) - Using the Simple (spl), Main (main) and Advanced (adv) profiles; the later is referred to as "Complex" in the VCM codec Therefore the files are named sb--q.avi