Essential dimension of semisimple groups of type $B$

We determine the essential dimension of an arbitrary semisimple group of type $B$ of the form $$G=(\mathrm{}(2n_1+1)\times \cdots \times \mathrm{}(2n_m+1))\mathrm{/}\mathit{\mu }$$ over a field of characteristic $0$, for all $n_1,\dots ,n_m\ge 7$, and a central subgroup $\mathit{\mu }$ of $\operatorname{$\mathbf{S}\mathbf{p}\mathbf{i}\mathbf{n}$}(2n_{1}+1)\times\cdots \times \operatorname{$\mathbf{S}\mathbf{p}\mathbf{i}\mathbf{n}$}(2n_{m}+1)$notcontainingthecenterof$\operatorname{$\mathbf{S}\mathbf{p}\mathbf{i}\mathbf{n}$}(2n_i+1)$ as a direct factor. We also find the essential dimension of $G$ for each of the following cases, where either $n_i=1$ for all $i$ or $m=2$, $n_1=1$, $2\le n_2\le 3$, $\mathit{\mu }$ is the diagonal central subgroup for both cases.