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USB camera module (USB) data storage format how to work?

author:admin time:2020-11-09 hits:451
USB data storage format


B. 1 file naming specification


The file name format of writing to USB device is "dxxxxxx"_ XXXX_ VDR "is divided into five sections, with the specific meanings as follows:


a) In the first section D, a one digit letter D is used to represent the data file;


b) The second section, XXXXXX, uses 6 digits to indicate the date and year of the recorder when collecting data, using 8421BCD code;


c) In the third section, 4 digits are used to indicate the time of recorder when collecting data, and 8421BCD code is used;


d) In the fourth section, XXXXXXXX, 1 Chinese character and 6 letters or numbers are used to indicate the license plate number set in the recorder


The character set of shall comply with GA 36 standard. If the license plate number is invalid, it will be filled with "unknown license plate";


e) In the fifth section, the suffix of data file is indicated by three character VDR.


B. 2 data storage Convention


When the recorder data is written into USB device, the following storage conventions shall be met:


a) The data in this appendix adopts hexadecimal code, 8421BCD code, ASC II character code and GB2312 character set (represented by euc-cn);


b) The scope of verification is all the bytes before the check byte, and its value is the XOR result of these bytes;


c) The storage space of USB device required in this appendix shall not be less than 1m bytes;


d) The file written to the USB device should at least contain the data content of the data block specified in table B.3.


B. 3 storage format


The file storage format of recorder writing to USB device is shown in table B.1, in which the number of data blocks refers to the number of different types of data blocks in the file, represented by 2 bytes, with the high bit in front and the low bit at the back.


The format definition of the data block in table B.1 is shown in table B.2, in which the data code refers to the representation code of the data block, expressed in one byte. The length of data record refers to the length of the data record contained in the data block, which is represented by 4 bytes, with the high bit first and the low bit last.


The definitions of data code, data name and data record in table B.2 are shown in table B.3, where data name refers to the name of data block.
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