[M4IF Technotes] Trouble with Bframe: size goes bigger

[Chen, Kenny]

I think if you've used a lot of B-frames in between I/P frames, the size of
cmp will increase in most cases.  Because the compression rate mostly
depends on the efficiency of motion estimation.  If the reference frame is
several frames away from current frame, the compression rate decreases in
most cases.
-----Original Message-----
From: Francesco Falconi [mailto:frans   inwind.it]
Sent: 2002?5?28? 20:13
To: technotes   lists.m4if.org
Subject: [M4IF Technotes] Trouble with Bframe: size goes bigger
Hello to everyone,
I hope someone can find two minutes to answer me. 
I show you this test: they are only 8 frames to compress, (frame base
cosing). My test is about advantage in size compression using more bframe
than Pframe. 
The GOP is 8 frame and i try to change the number of P-B frame (fixing numer
of Iframe).
So i change the value of  Motion.PBetweenICount  and Motion.BBetweenPCount 
These are the results:
P=    B=
GOP 
Size cmp
fps
0    6
I B B B B B B I
15944
0,4097
1    3
I B B B P B B I
14804
1,3095
3    1
I B P B P B P I
14065
2,4133
6    0
I P P P P P P I
14023
2,8229
I cant't understand why adding Bframe the size goes bigger, it could be the
opposite (accordin Mpeg Theory). I try to make other test, the same results.
Could you explain me the reason?
Thank you vaery much, this is for my university thesis.
Francesco Falconi
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