Research On Decoding Of VDR Audio Information

Voyage Data Recorder(VDR)can keep a record of audio information for ships underway.which helps to obtain reliable and accurate information concerning the cause and details of the accident,contribute to rebuild the cause chain of the accident,avoid the occurrence of similar accident through finding the real cause of the accident,consequently,consequently,improve the safety of maritime traffic.Due to the operating system version required by the running environment of the early VDR playback software is too old,the playback software can’t directly output sound files and Radar images,which is not convenient to use;,on the other hand,the electronic forensics and maritime investigation assistance system made by the maritime safety administration has its own independently intellectual property right,which means the playback software cannot be embedded in the system.Therefore,the study on decoding the VDR audio information is particularly important.Due to the wide variety of VDR products,different types of VDR have different information(text,audio,radar image,etc.)organization structure.Therefore,it is necessary to construct the corresponding organization structure decode driver,and obtain the audio information in the VDR information.Analyze recording format of audio information,determine the compression algorithm audio information use,and carry out the audio decoding.In this paper,information organization structure of Kevin Hughes VDR and an unknown VDR are respectively analyzed;the starting point of the audio information is found;compression algorithm used by audio information of two types of VDR are respectively ADPCM algorithm and Ogg/vorbis algorithm.The working principle of the two algorithms is deeply analyzed,taking Visual Studio 2013 as the development environment,the VDR audio decoding module has been developed.The audio decoding module can realize decoding,saving the decoded audio information as*.wav format.The results show that,the decoded audio finformation can be played normally to represent the audio recorded scene.Research achievements of this paper have been applied to the electronic forensics and maritime investigation assistance system,which assist the investigation of maritime traffic accident,provide objective comprehensive and detailed basis of the maritime administrative agency,analyze the cause of accident,and ascertain the responsibility for the maritime administrative agency investigation.