[x265] [PATCH] slicetype: Modify Scenecut algorithm to detect scene transition points
Deepthi Nandakumar
deepthi at multicorewareinc.com
Wed Jul 22 18:40:40 CEST 2015
The intention was to separate slicetype decision from scene change
detection, where scene change detection would also account for transitions
(like fade-ins, fade-outs etc), in addition to the abrupt scene change.
It is not clear to me how this is being done without modifying
scenecutInternal.
On Wed, Jul 22, 2015 at 9:59 PM, Steve Borho <steve at borho.org> wrote:
> On 07/22, aarthi at multicorewareinc.com wrote:
> > # HG changeset patch
> > # User Aarthi Thirumalai
> > # Date 1437505166 -19800
> > # Wed Jul 22 00:29:26 2015 +0530
> > # Node ID f134920ac855af45f052ccd6d3c239d39940a100
> > # Parent 46152345eb6ff261fd90272f7a0712300d6324c0
> > slicetype: Modify Scenecut algorithm to detect scene transition points
> > to improve Rate Control.
> >
> > identify scene trasitions, fade-ins, fadeouts, sceneCuts and signal the
> flag bSceneChange
> > in Lowres structure. This flag will be used by RateControl to adjust the
> wps during scene cuts.
> > No changes in sliceType decisions or I frame placement.
>
> I could nitpick a few coding style issues, but my main question is
> whether you tried disabling the keyframe distance bias during flash
> detection and arrived at this approach, or whether this is an orthogonal
> change?
>
> > diff -r 46152345eb6f -r f134920ac855 source/common/lowres.cpp
> > --- a/source/common/lowres.cpp Mon Jul 20 17:18:54 2015 -0700
> > +++ b/source/common/lowres.cpp Wed Jul 22 00:29:26 2015 +0530
> > @@ -127,6 +127,7 @@
> > {
> > bLastMiniGopBFrame = false;
> > bScenecut = true; // could be a scene-cut, until ruled out by
> flash detection
> > + bSceneChange = true;
> > bKeyframe = false; // Not a keyframe unless identified by lookahead
> > frameNum = poc;
> > leadingBframes = 0;
> > diff -r 46152345eb6f -r f134920ac855 source/common/lowres.h
> > --- a/source/common/lowres.h Mon Jul 20 17:18:54 2015 -0700
> > +++ b/source/common/lowres.h Wed Jul 22 00:29:26 2015 +0530
> > @@ -115,6 +115,7 @@
> > int leadingBframes; // number of leading B frames for P or I
> >
> > bool bScenecut; // Set to false if the frame cannot
> possibly be part of a real scenecut.
> > + bool bSceneChange;
> > bool bKeyframe;
> > bool bLastMiniGopBFrame;
> >
> > diff -r 46152345eb6f -r f134920ac855 source/encoder/slicetype.cpp
> > --- a/source/encoder/slicetype.cpp Mon Jul 20 17:18:54 2015 -0700
> > +++ b/source/encoder/slicetype.cpp Wed Jul 22 00:29:26 2015 +0530
> > @@ -462,6 +462,7 @@
> > m_pool = pool;
> >
> > m_lastNonB = NULL;
> > + m_isSceneTransition = false;
> > m_scratch = NULL;
> > m_tld = NULL;
> > m_filled = false;
> > @@ -1375,6 +1376,8 @@
> > bool Lookahead::scenecut(Lowres **frames, int p0, int p1, bool
> bRealScenecut, int numFrames, int maxSearch)
> > {
> > /* Only do analysis during a normal scenecut check. */
> > + int64_t avgSatdCost = 0;
> > + int cnt = 0;
> > if (bRealScenecut && m_param->bframes)
> > {
> > int origmaxp1 = p0 + 1;
> > @@ -1392,11 +1395,45 @@
> > for (int cp1 = p1; cp1 <= maxp1; cp1++)
> > {
> > if (!scenecutInternal(frames, p0, cp1, false))
> > + {
> > /* Any frame in between p0 and cur_p1 cannot be a real
> scenecut. */
> > for (int i = cp1; i > p0; i--)
> > + {
> > frames[i]->bScenecut = false;
> > + frames[i]->bSceneChange = false;
> > + }
> > + }
> > + else if (!scenecutInternal(frames,cp1 - 1, cp1, false))
> > + {
> > + /* Prevent false flashes. */
> > + frames[cp1]->bSceneChange = false;
> > + }
> > + else
> > + {
> > + /* compute average satdcost of flashes of scenecuts to
> confirm
> > + * bwhether a scene transition is possible within the
> segment. */
> > + avgSatdCost += frames[cp1]->costEst[1][0];
> > + cnt++;
> > + }
> > }
> > -
> > + /* Identify possible scene fluctuations by comparing the satd
> cost of the flashes.
> > + * This could denote the beginning or ending of scene
> transitions.
> > + * During a scene transition(fade in/fade outs), if fluctuate
> remains false,
> > + * then the scene had completed its transition or stabilized.
> > + */
> > + bool fluctuate = false;
> > + if (avgSatdCost > 0)
> > + {
> > + avgSatdCost /= cnt;
> > + for (int i= p0 ; i <= maxp1; i++)
> > + {
> > + if (abs(frames[i]->costEst[1][0] - avgSatdCost) > 0.1
> * avgSatdCost)
> > + {
> > + fluctuate = true;
> > + break;
> > + }
> > + }
> > + }
> > /* Where A-F are scenes: AAAAABBCCDDEEFFFFFF
> > * If each of BB ... EE are shorter than (maxp1-p0), they are
> > * detected as flashes and not considered scenecuts.
> > @@ -1405,8 +1442,23 @@
> > for (int cp0 = p0; cp0 <= maxp1; cp0++)
> > {
> > if (origmaxp1 > maxSearch || (cp0 < maxp1 &&
> scenecutInternal(frames, cp0, maxp1, false)))
> > + {
> > /* If cur_p0 is the p0 of a scenecut, it cannot be the
> p1 of a scenecut. */
> > frames[cp0]->bScenecut = false;
> > + /* Check for start of flash sequence for a new scene
> transition segment. */
> > + if (frames[cp0]->bSceneChange && !m_isSceneTransition
> && scenecutInternal(frames, cp0, cp0 + 1, false) && fluctuate)
> > + {
> > + m_isSceneTransition = true;
> > + }
> > + else
> > + frames[cp0]->bSceneChange = false;
> > + }
> > + }
> > +
> > + if (avgSatdCost == 0 || !fluctuate)
> > + {
> > + /* Signal end of scene transitioning */
> > + m_isSceneTransition = false;
> > }
> > }
> >
> > diff -r 46152345eb6f -r f134920ac855 source/encoder/slicetype.h
> > --- a/source/encoder/slicetype.h Mon Jul 20 17:18:54 2015 -0700
> > +++ b/source/encoder/slicetype.h Wed Jul 22 00:29:26 2015 +0530
> > @@ -127,7 +127,7 @@
> > int m_numCoopSlices;
> > int m_numRowsPerSlice;
> > bool m_filled;
> > -
> > + bool m_isSceneTransition;
> > Lookahead(x265_param *param, ThreadPool *pool);
> >
> > #if DETAILED_CU_STATS
> > _______________________________________________
> > x265-devel mailing list
> > x265-devel at videolan.org
> > https://mailman.videolan.org/listinfo/x265-devel
>
> --
> Steve Borho
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20150722/0058d4ea/attachment-0001.html>
More information about the x265-devel
mailing list