Think of Atmos as being made up of two parts: audio (data) and instructions on where to place the audio (metadata). The instructions part doesn't take up much space, so it can be the same for disc and streaming. But the audio part takes up lots of storage space and transmission bandwidth. So, the size of the soundtrack is shrunk using lossless packing (TrueHD) for disc and lossy compression (DD+) for streaming. But choice of compression codec has nothing to do with the instructions (channel assignments).Does dd+ preserve the channel assignments?