How do I only encode a portion of a video or clip out a portion of a video I submit?

To get only certain portions of your video encoded you should use either or parameters within the , or both of them.

The <start> tag may have a value in seconds from 0 up to the source media duration.
The <duration> tag should be not greater than the source duration less the start value.

For example, if the source video is 20 seconds and you need only last 10 seconds, use: <start>10</start> <duration>10</duration>