Decode binary file with a given data frame

Dear community, I am facing a lot of troubles as I am very inexperienced reading binary files. I want to decode a binary file and I know exactly the data frame.

So, in order to decode the header, I know that its size is 128 bytes. How can I proceed to retrieve each field given in the table?

Answer 1

[Pratyush Swain]

Hi César,

I understand you are facing problem in reading specific fields of binary files and you have prior knowledge regarding the dataframes existing in it such as size in bytes, offset and data type.

In this case, the 'fread' function and 'fseek' function together can help to decode the binary file.Please refer to the example implementation below:

% Writing a binary file with uint16 and int64 values

fileID = fopen('nine.bin','w');

fwrite(fileID,[1:9],'uint16');

fclose(fileID);

% Open the file in append mode

fileID = fopen('nine.bin','a');  

data = int64(10:18);

% Write int64 data to the end of the file

fwrite(fileID, data, 'int64'); 

% Close the file

fclose(fileID);

Now, lets try to read the different data type values.

fopen('nine.bin','r');
% Read uint16 values in the form of a matrix
values_uint16 = fread(fileID,[3,3],'uint16')

values_uint16 = 3×3

1 4 7 2 5 8 3 6 9

% We can also read the values in form of a column 

values_uint16 = fread(fileID,9,'uint16')

values_uint16 = 9×1

10 0 0 0 11 0 0 0 12

Please note the 'uint16' data type is of 2 bytes and we have 9 values in the beginning of file, so offset value becomes 9x2 = 18 bytes in order to access the next set of values.

% Using 'fseek' function to reach specific point in file
fseek(fileID,18,'bof'); % 'bof' signifies beginning of file
% Reading 'int64' data values
values_uint16 = fread(fileID,9,'int64')

values_uint16 = 9×1

10 11 12 13 14 15 16 17 18

We can perform similar type of operations for a file having variety of fields with different data types. For more information please refer to:

• https://www.mathworks.com/help/matlab/ref/fread.html

Hope this helps