When no video element is displayable (visibility is hidden or display is none),
audio level should be set to 0 and video should not be rendered.
-Video1 should be displayed between 0-4s, not rendered between 4-6 s and displayed between 6-10s.
-Video2 should be displayed between 0-2s, not rendered between 2-6 s and displayed between 6-10s.
-The audio of the video should be muted between 4-6s as no video is then rendered.
If the user agent does not support the 3GP media format, the test is still a pass.
