[MEncoder-users] CABAC and NoCABAC

[Stjepan Brbot]

On Tue, 2011-04-05 at 12:57 +0200, Grozdan wrote:
> On Tue, Apr 5, 2011 at 3:48 AM, Stjepan Brbot <stjepan.brbot at gmail.com> wrote:
> > I encoded the same movie twice; first time I had CABAC entropy coding
> > turned on and second time turned off. Although that resulted in
> > different file sizes, since entropy coding is lossless coding, I
> > expected the same PSNR for both encoded movies but psnr parameter
> > reported different figures!!! How's that possible?
> 
> Wait, so you're complaining of having different PSNR but are comparing
> two different coding schemes yet expect the exact same results? Are
> you serious?

No, you're wrong I'm talking about the same coding scheme. When video
compression coding is done then quantization coefficients, motion
vectors and reference indicies are coded in entropy coding using some of
lossless algorithms. This process of entropy coding is lossless and
taking different algorithms should affect only performance and
compression efficiency but all algorithms must keep the same entropy and
that should result in exactly the same input data for decoder.