The moving picture experts group (MPEG) video coding group started an immersive video coding standard project to accomplish acceptable bandwidth and decoding resources for multiple immersive videos with texture (color) and geometry (depth) information. The MPEG immersive video (MIV) coding standard provides functionality to remove inter-view redundancy and merge the residuals into videos defined as atlases. Although MIV reduces the number of videos to decode, an efficient decoder instance reduction method has not been investigated. This study proposes a frame packing implementation in MIV software. The proposed method conducts frame packing for geometry atlases to align with texture atlases, encodes them as subpicture bitstreams, and merges one texture / geometry atlas into a single bitstream with a bitstream merger. Furthermore, the proposed method provides control over the number of decoder instances without significantly increasing the computational complexity compared to existing frame packing methods. Therefore, the proposed method was accepted in MIV and will be implemented on the recent version of the reference software of MIV.