A Software Implementation Of Constrained Random Bitstream Generator For MPEG-4 Video

With the rapid development of computer network technology and mobile communication technology, digital video has become indispensable in people’s daily life. At the same time, people’s expectation on the video quality is getting higher and higher, and can’t tolerate the decoding errors(Bugs). Although the bit-streams can be generated from encoding the natural image sequences by a traditional video encoder, their functional coverage is not high enough because strong spatial and temporal correlations existed in the pixels and video parameters. And a functional coverage report can’t be generated in this way. So use these bit-streams to test the video decoder, the test time is too long and can’t guarantee the conformance test. Therefore, a big challenge for video decoder’s designer is how to guarantee the decoder’s correctness and conformance test in a shorter amount of time.A novel mechanism which based on SystemVerilog’s constrained random and functional coverage for video bit-stream generation is proposed. This video bit-stream generator could generate video bit-streams for decoder’s conformance test, stress test and robust test in some error cases.Firstly, a SystemVerilog constrained random video bit-stream generator is implemented. The generator employs the constrained-random techniques to produce highly randomized video parameters in its bit-stream and ignore the image’s strong spatial and temporal correlations. And this generator will sample the functional coverage when generate the bit-streams and generate the functional coverage reports which could be used in the decoder test.Secondly, a checker which extends from macro-soft’s MPEG-4 video decoder is implemented to double conform the generated bit-streams were followed the MPEG-4 video standard or not, or the error injections were consistent with the expected or not.Finally, a bit-stream selector is implemented to select the higher coverage bit-streams to construct a set which coverage is 100% to reduce the test time in decoder’s conformance test.