How to find the average of compression ratios of video manually?

Question

If the video coding standard is MPEG 1 and given frame sequence is 'IBBPBBPBBPBBI' and compression ratios for I,P,B are 0.1, 0.05 and 0.02 and video sequence is longer than 12 frames. What will be the average compression?
I am new in image processing and having difficulties to relate all the terms.How to find it?

Answer 1

This looks like homework, and so I'm tempted to not give you a straight answer.

That GOP structure you've shown has an I at both the front and the end. That indicates that this is then repeated. So your GOP will repeat the structure IBBPBBPBBPBB indefinitely.

The average compression would be how much each GOP is compressed compared to the original size of the 12 images. The size of the images as they come in are all the same - they are uncompressed video frames. The I frame is compressed to 0.1 of its original size. The P frames to 0.05 of its original size. The B frames to 0.02. For a GOP, you have 1 I picture, 3 P pictures and 8 B pictures. So the average ratio over a GOP is...?

Answer 2

So the answer will be (0.1*1+0.05*3+8*0.02)/12 = 0.0341 That means 0. 1 part of 1, 0.05 part of 3 and 0.02 part of 8 by total no of frames.