tests/streamgroups/mix_presentation-stereo

   1 type=iamf_mix_presentation:id=2:stg=0:annotations=en-us=Mix_Presentation,
   2 submix=parameter_id=100:parameter_rate=48000:default_mix_gain=1.0|element=stg=0:parameter_id=100:headphones_rendering_mode=stereo:annotations=en-us=Scalable_Submix|layout=sound_system=stereo:integrated_loudness=1.0,
   3 submix=parameter_id=100|element=stg=0:parameter_id=100:headphones_rendering_mode=binaural:default_mix_gain=1.0:annotations=en-us=Binaural_submix|layout=layout_type=binaural,