If you want to quickly check if the stream is video only, audio only or if it contains both audio and video, try hexdump -C filename | head
. The fifth byte contains information about the contents of the file.
0x01 - video only 0x04 - audio only 0x05 - audio + video
You can also try to play the file using VLC media player. There is a menu option that enables informational messages from the media being played back.