It is possible to view the video feed from many D-Link cameras in the free, open-source media player "VLC". http://www.videolan.org/vlc/index.html
The website claims support for Windows, Mac, Linux, iOS, Android, and others.
VLC is also great for playing most types of media such as movies, music, DVDs, etc.
To view the video stream (only, no audio):
In VLC, go to Media - Open Network Steam
For the Network URL, enter http://IPaddress:portnumber/video/mjpg.cgi (Where IPaddress and portnumber are the IP Address and port number for your camera.)
You will be prompted for your username and password, then the feed will start.
If you want to have an always-on-top video frame, you can set VLC to "Always On Top" in the Video menu, and "Minimal Interface" in the View menu.
You can also add your username and password to the URL to skip the login prompt like so: http://username:password@IPaddress:portnumber/video/mjpg.cgi
The audio stream is available separately at http://IPaddress:portnumber/audio.cgi
In my version of VLC, the video would play continuously, but the audio would play 30 seconds at a time.
There is also an option for playing two sources of media concurrently, but setting the Audio stream as a secondary media source would present two login prompts, but only the primary stream (video) would play.