The default recording profile uses 640 x 240 resolution for recording (so the ratio is 8:3, or 16:6). This was done to conserve CPU usage and reduce disk activity, in order to reduce dropped frames. If your have enough computer power, you can select a different profile. You can create custom recording profiles.
You can play the recorded 8:3 video in normal ratio by forcing aspect ratio back to 4:3 in player setting.