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-<profile>-q<quality>.avi