First u can use (show_group) param in your {categories} loop instead off {if} condition

      {categories show_group="4"}
        ......
      {/categories}

      {categories show_group="1"}
        ......
      {/categories}

and if you want to use {if} condition then change your code to :

      {categories}
        {if {category_group_id} == 4} {!-- formats --}
        ......
        {/if}
      {/categories}

      {categories}
        {if {category_group_id} == 1} {!-- formats --}
        ......
        {/if}
      {/categories}

the trick here is to around category_group_id variable with parentheses.

Regard's.

First u can use (show_group) param in your {categories} loop instead off {if} condition

      {categories show_group="4"}
        ......
      {/categories}

      {categories show_group="1"}
        ......
      {/categories}

and if you want to use {if} condition then change your code to :

      {categories}
        {if {category_group_id} == 4} {!-- formats --}
        ......
        {/if}
      {/categories}

      {categories}
        {if {category_group_id} == 1} {!-- formats --}
        ......
        {/if}
      {/categories}

the trick here is to around category_group_id variable with parentheses.

Note: this hack is in EE2.8.0 in another version maybe the line number will be different.

Regard's.