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Thread: SGram

  1. #1
    Join Date
    Jan 2014
    Bothell, Washington, USA
    Thanked 186 Times in 109 Posts


    I made this program to help me quickly visualize the nature of the contents of some files. It is called SGram and it creates colorized spectrograms or what I call stridegrams of a file. It is a command line windows program. To use it, the command is SGram log2FFTsize log2overlap maximumstride infile outfile. If maximumstride is 0, the program generates a spectrogram; otherwise it generates a stridegram. Here's an example, generated with "SGram 14 2 50 horse.vipm horse.bmp" (except I had to convert to .jpg to post):

    Click image for larger version. 

Name:	horse.jpg 
Views:	165 
Size:	16.6 KB 
ID:	4664

    The first part of the file is on the left and the last part of the file is on the right. The picture shows the file has a strong stride of 17 bytes for the first ~40% of the file, and then alternating sections with a stride of 2 byte data and 4 byte data.

    Here's another example, this time "SGram 15 3 500 calgary.tar calgary.bmp":

    Click image for larger version. 

Name:	calgary.jpg 
Views:	167 
Size:	277.4 KB 
ID:	4665

    Here, PIC stands out the most, showing a stride around 200 bytes and very quiet sections at the start and end. GEO is the section a little to the left of the middle that shows a stride at 4 bytes and what appear to be harmonics of a long stride of more than 500 bytes. OBJ1 and OBJ2 are the other section showing strides of 8 and 2 bytes.

    Lastly, here is "SGram 9 0 0 kennedy.xls kennedy.bmp":

    Click image for larger version. 

Name:	kennedy.jpg 
Views:	173 
Size:	930.9 KB 
ID:	4667

    kennedy.xls consistently has a stride of 13 bytes (13 stripes).
    Attached Files Attached Files

  2. Thanks (3):

    ne0n (29th September 2016),Shelwien (29th September 2016),willvarfar (29th September 2016)

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