Ecamm Live features special support for using a Canon DSLR for video, using just a USB cable. You can skip the extra hardware. Ecamm Live’s Canon DSLR feature supports just about every Canon DSLR camera.
Connect your Canon to your Mac via USB. You will now see your Canon show up as a video source in Ecamm Live’s Camera menu.
Connecting a Canon DSLR over USB will not give Ecamm Live access to your Canon's microphone. You'll need to use a different microphone.
See this Guide for detailed instructions and tips.