I found that the parameter passed to ma_data_source_read_pcm_frames in ma_decoder_read_pcm_frames is pDecoder->pBackend. But the ma_data_source_set_next and ma_data ...
This suggests the gateway requires a specific WS payload schema (field name, ordering, end-of-stream, or binary vs JSON) that is not documented on our side. A minimal working example of the first WS ...