Video sound in walkman mode

i've had the phone a year now but its only startin to annoy me now. When i use the walkman app and choose play all>random for example. I might get a video playing, not an actual video but the sound of my videos. So if i had a video of lets say a car revving and its in my videos folder, that sound from the video goes into my walkman and its used as a song.......does anyone know how i can stop this???
Can anyone help me???
SWard117