Benefits of webm? And can't play video on phones

I've been reading on webm on the net. It's a bit confusing on benefits of using it other than being more clear quality and open source. 

When I turn on 'Enable mobile playing' in flash apps, it starts converting to  .webm formats.  I suppose I should leave that option on just in case some mobile devices cannot play mp4 files but able to play webm files. Something to fall back to, correct? Perhaps I should leave that option on. 

My problem, currently is that webm files does not seem to be able to load on some mobile devices and browsers. I have html5 video player module installed. Only m4v files load. In my case, Safari browser on ipad mini is able to play the videos as it is playing mp4 video.

However, chrome browser installed on ipad is unable to play which I assume trying to play webm video file.

Chrome and android browser on my samsung galaxy phone unable to play assuming trying to play webm video file.

I know my phone browsers work because I am able to play video at newton's webpage http://www.recoverstormtreasures.com/m/videos/view/big-buck-bunny-504x284-2013-12-27

I have m4v and webm files on server. Anybody had these issues? Please advise or where to start looking into. 

Why didn't you post at original topic? Anyway...

WebM (VP9) not playable in Android browser, IE, Safari (both OS and iOS).

Thanks for pointing that out!

webm is used by desktop browsers instead of flash for the html5 player.

For mobile mp4 is used. And you must have the use H264 codec enabled in the flash app settings for it to work on mobile.

Halfway down this page is a chart showing the formats supported by what browsers and devices. http://mediaelementjs.com/

It's a different problem from the original topic. Thanks, Deano for the clarification that mobile devices don't use webm format. 

h264 is enabled on video player module as well as video comments....

M4V files may be encrypted with copyright for protection. Turn to TuneFab M4V Converter for help, it can convert M4V to MP4 so that you can play M4V files freely.