Testing av_opt_child_class_iterate()
AVIAMFAudioElement
  AVIAMFLayer
AVIAMFMixPresentation
  AVIAMFSubmix
    AVIAMFSubmixElement
      AVIAMFParamDefinition
        AVIAMFMixGain
        AVIAMFDemixingInfo
        AVIAMFReconGain
    AVIAMFSubmixLayout
    AVIAMFParamDefinition
      AVIAMFMixGain
      AVIAMFDemixingInfo
      AVIAMFReconGain
AVIAMFParamDefinition
  AVIAMFMixGain
  AVIAMFDemixingInfo
  AVIAMFReconGain

Testing av_opt_find2() with AV_OPT_SEARCH_CHILDREN | AV_OPT_SEARCH_FAKE_OBJ
AVIAMFAudioElement: default_w found
AVIAMFAudioElement: ch_layout found
AVIAMFMixPresentation: annotations found
AVIAMFMixPresentation: default_mix_gain found
AVIAMFMixPresentation: headphones_rendering_mode found
AVIAMFMixPresentation: sound_system found
AVIAMFMixPresentation: parameter_rate found
AVIAMFParamDefinition: parameter_rate found
AVIAMFParamDefinition: subblock_duration found
