[x265] [PATCH RFC] 1. Bug fix - improved quality drop for low resolution videos in ABR by 5%
Sumalatha Polureddy
sumalatha at multicorewareinc.com
Fri Sep 13 13:21:05 CEST 2013
modified according to comments in this thread
# HG changeset patch
# User sumalatha polureddy
# Date 1379070966 -19800
# Node ID 540be38baa71ba76e8502dbae8b8f4a4024cdb8d
# Parent 64cde4a0b1759e2033d99bec709db6acfbe0f07a
ratecontrol: Tweak to better handle short term compensation
Increase the coefficient cplxrSum is adjusted by so that short term
compensation does not suffer as much.
Also, clip the QP for the first frame.
Overall improvement is about 5%.
diff -r 64cde4a0b175 -r 540be38baa71 source/encoder/ratecontrol.cpp
--- a/source/encoder/ratecontrol.cpp Fri Sep 13 16:40:56 2013 +0530
+++ b/source/encoder/ratecontrol.cpp Fri Sep 13 16:46:06 2013 +0530
@@ -72,11 +72,12 @@
shortTermCplxCount = 0;
if (rateControlMode == X265_RC_ABR)
{
- //TODO : confirm this value. obtained it from x264 when crf is
disabled , abr enabled.
- //h->param.rc.i_rc_method == X264_RC_CRF ?
h->param.rc.f_rf_constant : 24 -- can be tweaked for x265.
-#define ABR_INIT_QP (24 + QP_BD_OFFSET)
+
+ //introduced to margin QP for first frame to an optimum level in
order to stabilize the quality.
+#define ABR_INIT_QP_MIN (24 + QP_BD_OFFSET)
+#define ABR_INIT_QP_MAX (38 + QP_BD_OFFSET)
accumPNorm = .01;
- accumPQp = (ABR_INIT_QP)*accumPNorm;
+ accumPQp = (ABR_INIT_QP_MIN) * accumPNorm;
/* estimated ratio that produces a reasonable QP for the first
I-frame */
cplxrSum = .01 * pow(7.0e5, qCompress) * pow(2 *ncu, 0.5);
wantedBitsWindow = bitrate * frameDuration;
@@ -86,7 +87,7 @@
pbOffset = 6.0 * (float)(X265_LOG2(param->rc.pbFactor));
for (int i = 0; i < 3; i++)
{
- lastQScaleFor[i] = qp2qScale(ABR_INIT_QP);
+ lastQScaleFor[i] = qp2qScale(ABR_INIT_QP_MIN);
lmin[i] = qp2qScale(MIN_QP);
lmax[i] = qp2qScale(MAX_QP);
}
@@ -111,15 +112,15 @@
switch (rateControlMode)
{
case X265_RC_ABR:
- {
- lastSatd = l->getEstimatedPictureCost(pic);
- double q = qScale2qp(rateEstimateQscale(rce));
- qp = Clip3(MIN_QP, MAX_QP, (int)(q + 0.5));
- rce->qpaRc = qpm = q;
- rce->newQp = qp;
- accumPQpUpdate();
- break;
- }
+ {
+ lastSatd = l->getEstimatedPictureCost(pic);
+ double q = qScale2qp(rateEstimateQscale(rce));
+ qp = Clip3(MIN_QP, MAX_QP, (int)(q + 0.5));
+ rce->qpaRc = qpm = q;
+ rce->newQp = qp;
+ accumPQpUpdate();
+ break;
+ }
case X265_RC_CQP:
qp = qpConstant[frameType];
@@ -160,16 +161,19 @@
{
/* B-frames don't have independent rate control, but rather get the
* average QP of the two adjacent P-frames + an offset */
+ TComSlice* prevRefSlice = curFrame->getRefPic(REF_PIC_LIST_0,
0)->getSlice();
+ TComSlice* nextRefSlice = curFrame->getRefPic(REF_PIC_LIST_1,
0)->getSlice();
+ bool i0 = prevRefSlice->getSliceType() == I_SLICE;
+ bool i1 = nextRefSlice->getSliceType() == I_SLICE;
+ int dt0 = abs(curFrame->getPOC() - prevRefSlice->getPOC());
+ int dt1 = abs(curFrame->getPOC() - nextRefSlice->getPOC());
+ double q0 = prevRefSlice->getSliceQp();
+ double q1 = nextRefSlice->getSliceQp();
- int i0 = curFrame->getRefPic(REF_PIC_LIST_0,
0)->getSlice()->getSliceType() == I_SLICE;
- int i1 = curFrame->getRefPic(REF_PIC_LIST_1,
0)->getSlice()->getSliceType() == I_SLICE;
- int dt0 = abs(curFrame->getPOC() -
curFrame->getRefPic(REF_PIC_LIST_0, 0)->getPOC());
- int dt1 = abs(curFrame->getPOC() -
curFrame->getRefPic(REF_PIC_LIST_1, 0)->getPOC());
-
- //TODO:need to figure out this
- double q0 = curFrame->getRefPic(REF_PIC_LIST_0,
0)->getSlice()->getSliceQp();
- double q1 = curFrame->getRefPic(REF_PIC_LIST_1,
0)->getSlice()->getSliceQp();
-
+ if (prevRefSlice->getSliceType() == B_SLICE &&
prevRefSlice->isReferenced())
+ q0 -= pbOffset / 2;
+ if (nextRefSlice->getSliceType() == B_SLICE &&
nextRefSlice->isReferenced())
+ q1 -= pbOffset / 2;
if (i0 && i1)
q = (q0 + q1) / 2 + ipOffset;
else if (i0)
@@ -183,12 +187,8 @@
q += pbOffset / 2;
else
q += pbOffset;
-
- double qScale = qp2qScale(q);
- lastQScaleFor[P_SLICE] = lastQScale = qScale/pbFactor;
-
- return qScale;
+ return qp2qScale(q);
}
else
{
@@ -242,21 +242,32 @@
q = qp2qScale(accumPQp / accumPNorm);
q /= fabs(ipFactor);
}
- else if (curFrame->getPOC() > 0)
+ if (rateControlMode != X265_RC_CRF)
{
- if (rateControlMode != X265_RC_CRF)
+ double lqmin = 0, lqmax = 0;
+
+ /* Clip the qp of 1st frame to ensure it doesnt detoriate the
quality */
+ if (curFrame->getPOC() == 0)
{
- /* Asymmetric clipping, because symmetric would prevent
- * overflow control in areas of rapidly oscillating
complexity */
- double lqmin = lastQScaleFor[pictType] / lstep;
- double lqmax = lastQScaleFor[pictType] * lstep;
- if (overflow > 1.1 && curFrame->getPOC() > 3)
- lqmax *= lstep;
- else if (overflow < 0.9)
- lqmin /= lstep;
+ lqmin = qp2qScale(ABR_INIT_QP_MIN) / lstep;
+ lqmax = qp2qScale(ABR_INIT_QP_MAX) * lstep;
+ double l1 = qScale2qp(lqmin);
+ double l2 = qScale2qp(lqmax);
+ l1=l2;
+ }
+ /* Asymmetric clipping, because symmetric would prevent
+ * overflow control in areas of rapidly oscillating complexity
*/
+ else if (curFrame->getPOC() > 0)
+ {
+ lqmin = lastQScaleFor[pictType] / lstep;
+ lqmax = lastQScaleFor[pictType] * lstep;
+ }
+ if (overflow > 1.1 && curFrame->getPOC() > 3)
+ lqmax *= lstep;
+ else if (overflow < 0.9)
+ lqmin /= lstep;
- q = Clip3(lqmin, lqmax, q);
- }
+ q = Clip3(lqmin, lqmax, q);
}
//FIXME use get_diff_limited_q() ?
@@ -300,16 +311,18 @@
if (rateControlMode == X265_RC_ABR)
{
if (frameType != B_SLICE)
- cplxrSum += 1.1 *bits * qp2qScale(rce->qpaRc) / rce->lastRceq;
+ /* The factor 1.5 is to tune up the actual bits, otherwise the
cplxrSum is scaled too low
+ * to improve short term compensation for next frame. */
+ cplxrSum += 1.5 *bits * qp2qScale(rce->qpaRc) / rce->lastRceq;
else
{
/* Depends on the fact that B-frame's QP is an offset from the
following P-frame's.
* Not perfectly accurate with B-refs, but good enough. */
- cplxrSum += bits * qp2qScale(rce->qpaRc) / (rce->lastRceq *
fabs(0.5 * pbFactor));
+ cplxrSum += bits * qp2qScale(rce->qpaRc) / (rce->lastRceq *
fabs(pbFactor));
}
cplxrSum *= cbrDecay;
wantedBitsWindow += frameDuration * bitrate;
- wantedBitsWindow *= cbrDecay;
+ wantedBitsWindow *= cbrDecay;
rce = NULL;
}
totalBits += bits;
On Fri, Sep 13, 2013 at 4:23 PM, Derek Buitenhuis <
derek.buitenhuis at gmail.com> wrote:
> On 9/13/2013 11:50 AM, Aarthi Priya Thirumalai wrote:
> > The qscale values are clipped(for P frames) depending on the
> lastQScaleFor[] at the end to ensure qps dont increase too high/low. they
> are updated in rateEstimateQScale for non B frames. The above change was
> introduced so that qp for P frames can adapt based on the qp of preceding
> B frames too - to see if its improves RateControl. Since it didnt give
> any big improvements, removing the change.
>
> Ah, OK then.
>
> - Derek
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
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