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 result borrows identities and effects from index. Vectors are sized exactly, so an evaluation allocates one scratch list plus one list per non-empty field.

Errors

Returns an error for mismatched indexes or unrepresentable retiming.