  We prove that a measure on $[-d, d]$ is the spectral measure of a factor of
i.i.d. process on a vertex-transitive infinite graph if and only if it is
absolutely continuous with respect to the spectral measure of the graph.
Moreover, we show that the set of spectral measures of factor of i.i.d.
processes and that of $\bar d_2$-limits of factor of i.i.d. processes are the
same.
