[x265] [PATCH] cutree: when cutree enabled P_SLICE CU QP always calculated from qpoffset,

[Gopu Govindaswamy]

Ok, Identified the root cause, the issue here is the reference state of the
reference frame getting changed during the encode,
this cause the CU QP is non-deterministic for this frame, and this is the
reason for inconsistent output when we use frame-threads > 1,

I have fixed this issue, and will send the patch

Thanks
Gopu G



On Thu, Apr 3, 2014 at 12:22 AM, Steve Borho <steve at borho.org> wrote:

> On Wed, Apr 2, 2014 at 12:52 AM,  <gopu at multicorewareinc.com> wrote:
> > # HG changeset patch
> > # User Gopu Govindaswamy
> > # Date 1396417894 -19800
> > #      Wed Apr 02 11:21:34 2014 +0530
> > # Node ID 931b4cd4da91dc667efd16d26b4e9ea834007623
> > # Parent  03bad90e94adce6fb89c6d5edb86919a1e783402
> > cutree: when cutree enabled P_SLICE CU QP always calculated from
> qpoffset,
> >
> > diff -r 03bad90e94ad -r 931b4cd4da91 source/encoder/frameencoder.cpp
> > --- a/source/encoder/frameencoder.cpp   Wed Apr 02 06:51:35 2014 +0530
> > +++ b/source/encoder/frameencoder.cpp   Wed Apr 02 11:21:34 2014 +0530
> > @@ -1228,7 +1228,17 @@
> >      int block_y = (cuAddr / m_pic->getPicSym()->getFrameWidthInCU()) *
> noOfBlocks;
> >      int block_x = (cuAddr * noOfBlocks) - block_y *
> m_pic->getPicSym()->getFrameWidthInCU();
> >
> > -    double *qpoffs = (m_pic->getSlice()->isReferenced() &&
> m_cfg->param->rc.cuTree) ? m_pic->m_lowres.qpOffset :
> m_pic->m_lowres.qpAqOffset;
> > +    double *qpoffs;
> > +    if (m_cfg->param->rc.cuTree)
> > +    {
> > +       if(m_pic->getSlice()->isReferenced() ||
> m_pic->getSlice()->getSliceType() == P_SLICE)
> > +           qpoffs = m_pic->m_lowres.qpOffset;
> > +       else
> > +           qpoffs = m_pic->m_lowres.qpAqOffset;
> > +    }
> > +    else
> > +       qpoffs = m_pic->m_lowres.qpAqOffset;
>
> Ok, I've realized qpOffset is the buffer holding the cuTree adjusted
> offsets while qpAqOffset has just the AQ adjustments (these variable
> names suck, but that is out-of-scope for this patch discussion)
>
> So the net effect of this patch is to treat all P slices as referenced
> and force them to use cuTree modified AQ offsets because apparently
> the reference flag is not deterministic.
>
> Your commit message was unclear, it should have looked more like this:
>
> """
> cutree: force P slices to use cuTree offsets, even if unreferenced
>
> We find that the referenced state of P frames is non-deterministic,
> leading to non-deterministic encodes.  This patch makes the encodes
> deterministic.
> """
>
> Then we could make a better evaluation on the merits of the patch, and
> the first thing that pops into my head is:  "Why is the reference
> state of P frames non-deterministic?" That is the root cause of the
> problem and it needs to be tackled next.  Once that is fixed this
> workaround can be backed out, since I see an equivalent patch was
> already applied.
>
> --
> Steve Borho
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>



-- 
Thanks & Regards
Gopu G
Multicoreware Inc
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