tv_scale(g->num_chunks, chunk_tv, &tmp); /* group duration */
tv_divide(fc->fcp->slices_per_group + fc->num_extra_slices,
&tmp, &g->slice_duration);
tv_scale(g->num_chunks, chunk_tv, &tmp); /* group duration */
tv_divide(fc->fcp->slices_per_group + fc->num_extra_slices,
&tmp, &g->slice_duration);