This is the captured demo for comparing progressive download and scalable streaming. The left windows illustrate progressive download, the user choose the "wrong" version of video. The quality is highest (layer index = 4), but the available bandwidth is insufficient to support the video. While the right side window shows the playback of scalable streaming, which adapts the video quality based on the client side buffer occupancy and  estimated available bandwidth. video link

The images below are the screenshot when the video is playing, the rate adaptation algorithm is adapting the video bitrate to the varying bandwidth. Therefore, we can expect that the video playback quality is changing as well. Please enlarge the image by clicking the images to see the different playback quality (layer index from 1 to 4.)
 320x180 layer index = 1
320x180 layer index = 2  
640x360 layer index = 3  
640x360 layer index = 4