Function evaluate 

pub fn evaluate<'a>(
    project: &Project,
    index: &'a ActiveIndex,
    time: MediaTime,
) -> Result<FrameDesc<'a>, EvalError>

Evaluates visual and audio clip descriptions at one timeline timestamp.

The description borrows identities and effects from index. Its vectors are sized exactly, so an evaluation allocates at most one scratch list and one list per non-empty field.

Errors

Returns an error for mismatched indexes or unrepresentable retiming.