You must use the YouTube API v2.0 - Using Batch Processing .
You can place the XML as follows:
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:media="http://search.yahoo.com/mrss/" xmlns:batch="http://schemas.google.com/gdata/batch" xmlns:yt="http://gdata.youtube.com/schemas/2007"> <batch:operation type="query" /> <entry> <id>http://gdata.youtube.com/feeds/api/videos/weRefE-qw9</id> </entry> <entry> <id>http://gdata.youtube.com/feeds/api/videos/kkT-t894YSa</id> </entry> ... </feed>
To this url:
http://gdata.youtube.com/feeds/api/videos/batch
This is a quote from the documentation:
The YouTube Data API supports batch processing, allowing you to perform up to 50 operations with a single API request, rather than submitting a separate request for each individual operation. A batch request processing can combine multiple requests (GET), insert (POST), update (PUT), and delete (DELETE). Each operation contained in the <entry> in the request. This section explains how to format batch processing requests and process API responses to these requests.
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