Lossless Compression Using Efficient Encoding of Bitmasks

Lossless compression is widely used to improve both memory requirement and communication bandwidth in embedded systems. Dictionary based compression techniques are very popular because of their good compression efficiency and fast decompression mechanism. Bitmask based compression improves the effectiveness of the dictionary based approaches by recording minor differences using bitmasks. This paper proposes an efficient encoding of bitmasks used in bitmask-based compression. We prove that a n-bit bitmask (records n differences) can be encoded using only n-1 bits. This encoding improves compression efficiency while reduces decompression hardware overhead. We have applied our approach in a wide a variety of domains including code compression, FPGA bitstream compression as well as control word compression. Our experimental results using a wide variety of benchmarks demonstrate that our approach improves the compression efficiency by 3 to 10% without adding any additional decompression overhead.