Pixels in 360p video

[Nanley]

Hello, i'm using 2.2.1 portable version. The video i downloaded from youtube is in 360p resolution. Codec information shows h.264 MPEG4-AVC. When i play it in my editing program, it looks fine, but when i open it in VLC huge pixels appear. Occasionally they disappear, but it's just for a second and always at the same moments. Something with shadows or lightning? I have tried to disable hardware acceleration, played with codec options, but nothing helped.