Videos without sounds

Why there is sometimes if we send videos from PC to ipod classic, we just can watch videos without sounds? It may lokks weird but it does happen to some ipod classic users.

Does the video have sound in the first place? Maybe its because the format of the file has been updated and its too new for the classic.

I've never even heard of iPod videos without sound. Could you name a few?

What do you mean j.chang. I cannot get your question

I think the video format is not ipod supported. I have no problem with that so far

I think some configurations should be made, but i never had same problem with yours