a property

num a

@override
num get a => numChannels > 3 ? Float16.float16ToDouble(data[_index + 3]) : 0;

void a=(num a)

@override
set a(num a) {
  if (numChannels > 3) {
    final d = g.toDouble();
    data[_index + 3] = Float16.doubleToFloat16(d);
  }
}