SGram

[Kennon Conrad]

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):



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":



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":



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