.dbmd files are required when converting from .atmos or .rpl to .wav (ADM BWF) only if you need to change the default Dolby Digital Plus Encoding Metadata,  Atmos Downmix Metadata, and Atmos Supplemental Metadata from the default values. In the majority of cases this is not required but check your delivery specifications to be sure. If you do need to modify these values either use the .dbmd file from the Renderer v3.0 or copy the output.atmos.dbmd file to the same directory location as your .atmos, .atmosmetadata, and .atmos.audio and rename the file from "output" to the shared base filename of the other three files.


The default values are:  


ddplus:
  lorocmixlev: -3dB
  lorosurmixlev: -3dB
  ltrtcmixlev: -3dB
  ltrtsurmixlev: -3dB
  dsurexmod: not_indicated
  compr1: film_light
  dynrng1: film_light
atmos:
  downmix_type_5to2: not_indicated
  downmix_type_7to5: not_indicated
atmos_supplemental:
  object_count: 0
  trim_metadata:
    trim_config_data:
      {}
    trim_bypass_data:
      []
  headphone_metadata:
    []