BINK movies are widely used in games because they provide transparency in the video from long back. Sometime you have to reverse engineer the BINK file and get the PNGs out of (not JPEG but PNG with transparency) the movie. I've used FFMpeg to get PNGs out of BINK (.bik format) file as followed.
1. Download latest ffmpeg static build from http://ffmpeg.zeranoe.com/builds/
2. Extract the .7z build to any folder.
3. Give this command to convert “my.bik” to “output” folder and %d is sequence number in output image. %d will auto increment by one, you have to just give %d in the command.
ffmpeg.exe -i D:\my.bik D:\output\my_%d.png
Note that this is a general command which applies to any type of movie format supported by ffmpeg. There are hell lot of more things you can with ffmpeg. For example, your popular VLC is built using ffmpeg library :)