field content template

hi I don't know exactly what to ask so I'll explain. I'm making a site where people can add videos from sources like youtube or google video directly into a post, I'm using the wordpres video plugin and the way it works is that the viedo is embed with a shortcode like [youtube videoID width height] and for google video is [google videoID] The fist thing I tried was for the user to put the video id into a text field and put it on the content via content template, and use the field of the video source so the content template ended something like this: [{Source::5} {ID video:19} 500 400] but the problem is that google video doesnt work with width and height so the video wont show. The next thing I tried was to make sa separate field for each kind of source, to show with conditional logic and put all of the sources on the content template but the problem was than i ended with extra strings like this [ 500 400], so i thougt that with a custom fiel i could create a content template for that field and use it on the post content template, but it didn't work, the field doesnt apear at all on the content, so i see two solutions one is to use the value of a drop down field on the content template, so i could populate it with something like 500 400] and use it on the post content template, that or is there a way to save a field depending on the value that is entered, for example if i enter "www.youtube.com/watch?v=l8DQCBewszY" the field gets saved like [youtube l8DQCBewszY 500 400] and if I enter "http://video.google.com/videoplay?docid=8883910961351786332" the field gets saved like [google 8883910961351786332] or maybe there is an easier way to make embed videos through a gravity forms field? thanks!

this is my form http://consiente.org/new