Open Radar

 
Summary:
* HTML5 audio and video will not automatically play (even from the "ended" event of another media file) if the tab is not in the foreground
* For example, on the new HTML5-based Pandora radio website, if you are playing a station in Safari 5.1 and switch to another tab, the music will not automatically advance to the next song in the playlist until you switch back to the tab

Steps to Reproduce:
1) Load the following example page which uses code taken verbatim from Apple's documentation, which demonstrates linked media playing (starting media from the "ended" event of another):
http://novakowski.net/apple.html
2) Click on the "play" control for the video and before it finishes, switch to another tab in Safari

Expected Results:
* Second video should automatically play after the first has ended

Actual Results:
* Second video does not automatically play until you switch back to the tab

Regression:
* We don't have older versions of Safari to test with, but we're pretty sure this was an issue with Safari 5.0 as well

Notes:
* This bug has a major impact on sites such as ours which rely on the ability to chain individual media files together into a single audio stream