Research And Realization Of Audio Signal Long-range Acquisition System Of VDR Based On Ethernet

Voyage Data Recorder (VDR for short) is a special instrument which could record the statement of the important equipments of ships. After the catastrophic accident for marine voyage, the datum recorded by VDR could be used to analyse and look for the cause of the accident. Recording the voice of ship cabin and communication voice of the VHF is one of the important items, which VDR has to record. The high quality acquisition to voice signal have an important significance to recover the status of an accident and analyse the cause.When ships are sailing, the environment is usually complex, and audio signals are all analog signals which can not be transmitted at long bowls. Another feature of audio acquisition is that the amount of data is very big. So in order to overcome these shortcomings and realize the audio acquisition of VDR equipment, this paper raised a new idea of long-range acquisition.Firstly, this paper gave a comparison of various audio encoding algorithms and then chose two fit algorithms according to specific requirements and related standards of VDR. Secondly, this paper did an in-depth study of the two encoding technologys which are PCM and SB-ADPCM, and stated detailed their every part. Combined the actual requirements of the VDR project, this paper raised the scheme that connecting the VDR host and audio acquisition card with Ethernet. By this scheme, the hard audio acquisition card as slave system was designed. So the encoding software, receiving and storage software of host computer were finished in this equipment. At last, we debugged all this system, and tested its performance according to some standards.