How can I edit my code so that my custom field is the ID code of a YouTube video (e.g. s6jaYJx7yeI) and it is automatically output as an embedded video.
That is, the custom field is automatically inserted into here:
<iframe width="420" height="315" src="http://www.youtube.com/embed/CUSTOMFIELDVALUEHERE" frameborder="0" allowfullscreen></iframe>
All of the different things I've tried with custom field either kill the iframe callout or block off the code at /embed. I can't seem to get it neatly inserted into the source callout. Help!