<div dir="ltr"><div>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. <br><br></div>It is not clear to me how this is being done without modifying scenecutInternal.<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 22, 2015 at 9:59 PM, Steve Borho <span dir="ltr"><<a href="mailto:steve@borho.org" target="_blank">steve@borho.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On 07/22, <a href="mailto:aarthi@multicorewareinc.com">aarthi@multicorewareinc.com</a> wrote:<br>
> # HG changeset patch<br>
> # User Aarthi Thirumalai<br>
> # Date 1437505166 -19800<br>
> # Wed Jul 22 00:29:26 2015 +0530<br>
> # Node ID f134920ac855af45f052ccd6d3c239d39940a100<br>
> # Parent 46152345eb6ff261fd90272f7a0712300d6324c0<br>
> slicetype: Modify Scenecut algorithm to detect scene transition points<br>
> to improve Rate Control.<br>
><br>
> identify scene trasitions, fade-ins, fadeouts, sceneCuts and signal the flag bSceneChange<br>
> in Lowres structure. This flag will be used by RateControl to adjust the wps during scene cuts.<br>
> No changes in sliceType decisions or I frame placement.<br>
<br>
</span>I could nitpick a few coding style issues, but my main question is<br>
whether you tried disabling the keyframe distance bias during flash<br>
detection and arrived at this approach, or whether this is an orthogonal<br>
change?<br>
<div class="HOEnZb"><div class="h5"><br>
> diff -r 46152345eb6f -r f134920ac855 source/common/lowres.cpp<br>
> --- a/source/common/lowres.cpp Mon Jul 20 17:18:54 2015 -0700<br>
> +++ b/source/common/lowres.cpp Wed Jul 22 00:29:26 2015 +0530<br>
> @@ -127,6 +127,7 @@<br>
> {<br>
> bLastMiniGopBFrame = false;<br>
> bScenecut = true; // could be a scene-cut, until ruled out by flash detection<br>
> + bSceneChange = true;<br>
> bKeyframe = false; // Not a keyframe unless identified by lookahead<br>
> frameNum = poc;<br>
> leadingBframes = 0;<br>
> diff -r 46152345eb6f -r f134920ac855 source/common/lowres.h<br>
> --- a/source/common/lowres.h Mon Jul 20 17:18:54 2015 -0700<br>
> +++ b/source/common/lowres.h Wed Jul 22 00:29:26 2015 +0530<br>
> @@ -115,6 +115,7 @@<br>
> int leadingBframes; // number of leading B frames for P or I<br>
><br>
> bool bScenecut; // Set to false if the frame cannot possibly be part of a real scenecut.<br>
> + bool bSceneChange;<br>
> bool bKeyframe;<br>
> bool bLastMiniGopBFrame;<br>
><br>
> diff -r 46152345eb6f -r f134920ac855 source/encoder/slicetype.cpp<br>
> --- a/source/encoder/slicetype.cpp Mon Jul 20 17:18:54 2015 -0700<br>
> +++ b/source/encoder/slicetype.cpp Wed Jul 22 00:29:26 2015 +0530<br>
> @@ -462,6 +462,7 @@<br>
> m_pool = pool;<br>
><br>
> m_lastNonB = NULL;<br>
> + m_isSceneTransition = false;<br>
> m_scratch = NULL;<br>
> m_tld = NULL;<br>
> m_filled = false;<br>
> @@ -1375,6 +1376,8 @@<br>
> bool Lookahead::scenecut(Lowres **frames, int p0, int p1, bool bRealScenecut, int numFrames, int maxSearch)<br>
> {<br>
> /* Only do analysis during a normal scenecut check. */<br>
> + int64_t avgSatdCost = 0;<br>
> + int cnt = 0;<br>
> if (bRealScenecut && m_param->bframes)<br>
> {<br>
> int origmaxp1 = p0 + 1;<br>
> @@ -1392,11 +1395,45 @@<br>
> for (int cp1 = p1; cp1 <= maxp1; cp1++)<br>
> {<br>
> if (!scenecutInternal(frames, p0, cp1, false))<br>
> + {<br>
> /* Any frame in between p0 and cur_p1 cannot be a real scenecut. */<br>
> for (int i = cp1; i > p0; i--)<br>
> + {<br>
> frames[i]->bScenecut = false;<br>
> + frames[i]->bSceneChange = false;<br>
> + }<br>
> + }<br>
> + else if (!scenecutInternal(frames,cp1 - 1, cp1, false))<br>
> + {<br>
> + /* Prevent false flashes. */<br>
> + frames[cp1]->bSceneChange = false;<br>
> + }<br>
> + else<br>
> + {<br>
> + /* compute average satdcost of flashes of scenecuts to confirm<br>
> + * bwhether a scene transition is possible within the segment. */<br>
> + avgSatdCost += frames[cp1]->costEst[1][0];<br>
> + cnt++;<br>
> + }<br>
> }<br>
> -<br>
> + /* Identify possible scene fluctuations by comparing the satd cost of the flashes.<br>
> + * This could denote the beginning or ending of scene transitions.<br>
> + * During a scene transition(fade in/fade outs), if fluctuate remains false,<br>
> + * then the scene had completed its transition or stabilized.<br>
> + */<br>
> + bool fluctuate = false;<br>
> + if (avgSatdCost > 0)<br>
> + {<br>
> + avgSatdCost /= cnt;<br>
> + for (int i= p0 ; i <= maxp1; i++)<br>
> + {<br>
> + if (abs(frames[i]->costEst[1][0] - avgSatdCost) > 0.1 * avgSatdCost)<br>
> + {<br>
> + fluctuate = true;<br>
> + break;<br>
> + }<br>
> + }<br>
> + }<br>
> /* Where A-F are scenes: AAAAABBCCDDEEFFFFFF<br>
> * If each of BB ... EE are shorter than (maxp1-p0), they are<br>
> * detected as flashes and not considered scenecuts.<br>
> @@ -1405,8 +1442,23 @@<br>
> for (int cp0 = p0; cp0 <= maxp1; cp0++)<br>
> {<br>
> if (origmaxp1 > maxSearch || (cp0 < maxp1 && scenecutInternal(frames, cp0, maxp1, false)))<br>
> + {<br>
> /* If cur_p0 is the p0 of a scenecut, it cannot be the p1 of a scenecut. */<br>
> frames[cp0]->bScenecut = false;<br>
> + /* Check for start of flash sequence for a new scene transition segment. */<br>
> + if (frames[cp0]->bSceneChange && !m_isSceneTransition && scenecutInternal(frames, cp0, cp0 + 1, false) && fluctuate)<br>
> + {<br>
> + m_isSceneTransition = true;<br>
> + }<br>
> + else<br>
> + frames[cp0]->bSceneChange = false;<br>
> + }<br>
> + }<br>
> +<br>
> + if (avgSatdCost == 0 || !fluctuate)<br>
> + {<br>
> + /* Signal end of scene transitioning */<br>
> + m_isSceneTransition = false;<br>
> }<br>
> }<br>
><br>
> diff -r 46152345eb6f -r f134920ac855 source/encoder/slicetype.h<br>
> --- a/source/encoder/slicetype.h Mon Jul 20 17:18:54 2015 -0700<br>
> +++ b/source/encoder/slicetype.h Wed Jul 22 00:29:26 2015 +0530<br>
> @@ -127,7 +127,7 @@<br>
> int m_numCoopSlices;<br>
> int m_numRowsPerSlice;<br>
> bool m_filled;<br>
> -<br>
> + bool m_isSceneTransition;<br>
> Lookahead(x265_param *param, ThreadPool *pool);<br>
><br>
> #if DETAILED_CU_STATS<br>
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<br>
</div></div><span class="HOEnZb"><font color="#888888">--<br>
Steve Borho<br>
</font></span><div class="HOEnZb"><div class="h5">_______________________________________________<br>
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</div></div></blockquote></div><br></div>