[MEncoder-users] How important are B-frames?

[Janos Szamosfalvi]

--- On Thu, 5/10/12, Gabri Nurtinaz Shally <gabri.ns at gmail.com> wrote:

> From: Gabri Nurtinaz Shally <gabri.ns at gmail.com>
> Subject: Re: [MEncoder-users] How important are B-frames?
> To: "MEncoder usage discussions" <mencoder-users at mplayerhq.hu>
> Date: Thursday, May 10, 2012, 11:14 AM
> On May 11, 2012 1:02 AM, "Janos
> Szamosfalvi" <szamosj at yahoo.com>
> wrote:
> >
> >
> >
> > --- On Thu, 5/10/12, Sylvester <sylvester821994 at gmail.com>
> wrote:
> >
> > B-frames are most useful when there's little movement,
> > so you may want to repeat the test with a video that
> > doesn't have lots of movement if you want to know the
> > effect of B-frames on file size.
> >
> 
> especially cartoon or anime.
> 
> btw, from reported frame, there is difference. take a look
> at QP parameter on I-frame. when the bframes set to 3, the 
> QP value were 31, but it is reduced to 32 when bframes set 
> to 0. from this information, imo, bframes save bits so that 
> it can be used to improve quality of I-frames.

I did a bit of testing to see what happens with different bframes 
settings. There's a significant reduction in size and jump in 
quality from 0 to 1, but the effect of additional bframes is 
a bit dubious.  And mencoder crashed with bframes=4....  :( 

See attached .txt for full result.  

I also attached a small image from excel to show the important 
parameters: size and SSIM.  Note: on the x axis, 1 corresponds to bframes=0, 2 to 1, 3 to 2 and 4 to 3.

Of course results can easily be different with different settings 
and a different file, but IMHO, as long as bframes are supported, 
at the very least, bframes=1 should be used. 
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