amr_parse_mr_conf() <- 20 a5 0d 46 52 54 
amr_parse_mr_conf() -> num_modes=4
  Mode[0] = 0/13/4
  Mode[1] = 2/25/4
  Mode[2] = 5/37/4
  Mode[3] = 7/0/0
amr_parse_mr_conf() <- 20 ff 0d 46 52 54 
amr_parse_mr_conf() <- ff ff 0d 46 52 54 
amr_parse_mr_conf() <- ff