Question

I wish to know how to calculate the difference among two video timecodes tha are in frames (in this case, a second equals 30 frames).

Let say the point A is 600 (00:00:02) and the point B is 120 (00:00:04).

How can I calculate the difference among pont A and B and echo the result in the 00:00:00.00 format (h:m:s) using bash?

---

UPDATE:

This is perfection: http://www.1728.com/angle.htm

Answer 1

First off, the export statements are redundant since the current shell is expanding $A and $B.

To get those numbers from the timestamps, GNU date will help:

jinx:752 Z$ date -d 00:01:18.44 +%T.%N # to show that it works
00:01:18.440000000
jinx:753 Z$ date -d 00:01:18.44 +%s.%N
1299214878.440000000

Now you can do your calculations, then translate back at the end for display (as Edwin Buck said, don’t try to store intermediate results in this format):

jinx:754 Z$ date -d @1299214878.44 +%T.%N
00:01:18.440000000