Invert the bit packing order on SP data. Normally bits are little endian ordered. The first sample is in bit=0, second in bit=1 ... bit=7. With the BIGEND flag, the first sample is bit=7, second sample is bit=6, ... bit=0. When running under X-Midas, the default bit-packing is BIGEND. Under NeXtMidas and non-Midas, the default is little endian.