Is there a technical explanation for the I-frame setting? I do notice when I change the FPS, the I-frame changes with it, but why is it even an option to change?
I frames are the "key" frames with the most data.
The typical Group Of Pictures (GOP) structure is IBBPBBP... The I-frame is used to predict the first P-frame and these two frames are also used to predict the first and the second B-frame. The second P-frame is predicted using the first P-frame and they join to predict the third and fourth B-frames. The scheme is shown in the next picture:
View attachment 118
This structure suggests a problem because the fourth frame (a P-frame) is needed in order to predict the second and the third (B-frames). So we need to transmit the P-frame before the B-frames and it will delay the transmission (it will be necessary to keep the P-frame).
Example of a GOP structure
This structure has strong points:
##It minimizes the problem of possible uncovered areas.
##P-frames and B-frames need less data than I-frames, so less data is transmitted.
But it has weak points:
##It increases the complexity of the decoder, which can mean more memory is needed to rearrange the frames.
##The interpolated frames (namely B-frames) require more motion vectors which means an increased bit rate.
Clear as mud!!! The more I frames the more bandwidth is used. But when you have fast motion it is better.