The SLT-A57 supports a maximum video resolution of 1920 x 1080 pixels. That's over two times the video resolution of the most frequently found video resolution of 1280 x 720 pixels. In addition, this camera support a video resolution of 640 x 480 pixels and 1440 x 1080 pixels. A video resolution of 1920 x 1080 pixels is equivalent to Full HD video. You will require a Full HD TV or better to appreciate this level of detail.
This camera's video resolution (1920 x 1080 pixels) is actually the best supported video resolution across all SLR cameras that have been on the market for around the same time as the SLT-A57.
The worst supported video resolution amongst comparable types of camera is 320 x 240 pixels.