[x265] [PATCH 1 of 2] slicetype: Modify Scenecut algorithm to detect scene transition points
Steve Borho
steve at borho.org
Mon Aug 17 08:14:32 CEST 2015
On 08/17, aarthi at multicorewareinc.com wrote:
> # HG changeset patch
> # User Aarthi Thirumalai
> # Date 1437505166 -19800
> # Wed Jul 22 00:29:26 2015 +0530
> # Node ID 51320561d41f32faa75dd3d04d88ea68500ce995
> # Parent d56b2466c04459205287e1581d8a36eebf372ba6
> slicetype: Modify Scenecut algorithm to detect scene transition points
> to improve Rate Control (refs #160).
>
> identify scene trasitions, fade-ins, fadeouts, sceneCuts and signal the flag bSceneCut
> in Lowres structure. This flag will be used by RateControl to adjust the wps during scene cuts.
'wps' typo
are these two patches ok for the stable branch?
> diff -r d56b2466c044 -r 51320561d41f source/common/lowres.cpp
> --- a/source/common/lowres.cpp Wed Aug 12 18:12:20 2015 +0530
> +++ b/source/common/lowres.cpp Wed Jul 22 00:29:26 2015 +0530
> @@ -126,7 +126,7 @@
> void Lowres::init(PicYuv *origPic, int poc)
> {
> bLastMiniGopBFrame = false;
> - bScenecut = true; // could be a scene-cut, until ruled out by flash detection
> + bScenecut = false; // could be a scene-cut, until ruled out by flash detection
> bKeyframe = false; // Not a keyframe unless identified by lookahead
> frameNum = poc;
> leadingBframes = 0;
> diff -r d56b2466c044 -r 51320561d41f source/encoder/slicetype.cpp
> --- a/source/encoder/slicetype.cpp Wed Aug 12 18:12:20 2015 +0530
> +++ b/source/encoder/slicetype.cpp Wed Jul 22 00:29:26 2015 +0530
> @@ -483,6 +483,7 @@
> m_pool = pool;
>
> m_lastNonB = NULL;
> + m_isSceneTransition = false;
> m_scratch = NULL;
> m_tld = NULL;
> m_filled = false;
> @@ -1267,10 +1268,16 @@
>
> int numBFrames = 0;
> int numAnalyzed = numFrames;
> - if (m_param->scenecutThreshold && scenecut(frames, 0, 1, true, origNumFrames, maxSearch))
> +
> + if (m_param->bFrameAdaptive)
> {
> - frames[1]->sliceType = X265_TYPE_I;
> - return;
> + bool isScenecut = scenecut(frames, 0, 1, true, origNumFrames);
> + /* When scenecut threshold is set, use scenecut detection for I frame placements */
> + if (!m_param->scenecutThreshold && isScenecut)
> + {
> + frames[1]->sliceType = X265_TYPE_I;
> + return;
> + }
> }
>
> if (m_param->bframes)
> @@ -1357,14 +1364,13 @@
> /* Check scenecut on the first minigop. */
> for (int j = 1; j < numBFrames + 1; j++)
> {
> - if (m_param->scenecutThreshold && scenecut(frames, j, j + 1, false, origNumFrames, maxSearch))
> + if (m_param->scenecutThreshold && scenecut(frames, j, j + 1, false, origNumFrames))
> {
> frames[j]->sliceType = X265_TYPE_P;
> numAnalyzed = j;
> break;
> }
> }
> -
> resetStart = bKeyframe ? 1 : X265_MIN(numBFrames + 2, numAnalyzed + 1);
> }
> else
> @@ -1388,46 +1394,97 @@
> if (bIsVbvLookahead)
> vbvLookahead(frames, numFrames, bKeyframe);
>
> + int maxp1 = X265_MIN(m_param->bframes + 1, origNumFrames);
> /* Restore frame types for all frames that haven't actually been decided yet. */
> for (int j = resetStart; j <= numFrames; j++)
> + {
> frames[j]->sliceType = X265_TYPE_AUTO;
> + /* If any frame marked as scenecut is being restarted for sliceDecision,
> + * undo scene Transition flag */
> + if (j <= maxp1 && frames[j]->bScenecut && m_isSceneTransition)
> + m_isSceneTransition = false;
> + }
> }
>
> -bool Lookahead::scenecut(Lowres **frames, int p0, int p1, bool bRealScenecut, int numFrames, int maxSearch)
> +bool Lookahead::scenecut(Lowres **frames, int p0, int p1, bool bRealScenecut, int numFrames)
> {
> /* Only do analysis during a normal scenecut check. */
> if (bRealScenecut && m_param->bframes)
> {
> int origmaxp1 = p0 + 1;
> /* Look ahead to avoid coding short flashes as scenecuts. */
> - if (m_param->bFrameAdaptive == X265_B_ADAPT_TRELLIS)
> - /* Don't analyse any more frames than the trellis would have covered. */
> - origmaxp1 += m_param->bframes;
> - else
> - origmaxp1++;
> + origmaxp1 += m_param->bframes;
> int maxp1 = X265_MIN(origmaxp1, numFrames);
> -
> + bool fluctuate = false;
> + bool noScenecuts = false;
> + int64_t avgSatdCost = 0;
> + if (frames[0]->costEst[1][0] > -1)
> + avgSatdCost = frames[0]->costEst[1][0];
> + int cnt = 1;
> /* Where A and B are scenes: AAAAAABBBAAAAAA
> * If BBB is shorter than (maxp1-p0), it is detected as a flash
> * and not considered a scenecut. */
> 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;
> + noScenecuts = false;
> + }
> + }
> + else if (scenecutInternal(frames, cp1 - 1, cp1, false))
> + {
> + /* If current frame is a Scenecut from p0 frame as well as Scenecut from
> + * preceeding frame, mark it as a Scenecut */
> + frames[cp1]->bScenecut = true;
> + noScenecuts = true;
> + }
> +
> + /* compute average satdcost of all the frames in the mini-gop to confirm
> + * whether there is any great fluctuation among them to rule out false positives */
> + X265_CHECK(frames[cp1]->costEst[cp1 - p0][0]!= -1, "costEst is not done \n");
> + avgSatdCost += frames[cp1]->costEst[cp1 - p0][0];
> + cnt++;
> }
> + /* Identify possible scene fluctuations by comparing the satd cost of the frames.
> + * 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.
> + */
>
> - /* 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.
> - * Instead, the first F frame becomes a scenecut.
> - * If the video ends before F, no frame becomes a scenecut. */
> - for (int cp0 = p0; cp0 <= maxp1; cp0++)
> + if (noScenecuts)
> {
> - 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;
> + fluctuate = false;
> + avgSatdCost /= cnt;
> + for (int i= p1 ; i <= maxp1; i++)
> + {
> + if (abs(frames[i]->costEst[i - p0][0] - avgSatdCost) > 0.1 * avgSatdCost)
> + {
> + fluctuate = true;
> + if (!m_isSceneTransition && frames[i]->bScenecut)
> + {
> + m_isSceneTransition = true;
> + /* just mark the first scenechange in the scene transition as a scenecut. */
> + for (int j = i + 1; j <= maxp1; j++)
> + {
> + frames[j]->bScenecut = false;
don't need braces here or below
> + }
> + break;
> + }
> + }
> + if (frames[i]->bScenecut)
> + {
> + frames[i]->bScenecut = false;
> + }
this assignment can be done unconditionally
> + }
> + }
> + if (!fluctuate && !noScenecuts)
> + {
> + /* Signal end of scene transitioning */
> + m_isSceneTransition = false;
> }
> }
>
> @@ -1451,22 +1508,23 @@
>
> /* magic numbers pulled out of thin air */
> float threshMin = (float)(threshMax * 0.25);
> - float bias;
> -
> - if (m_param->keyframeMin == m_param->keyframeMax)
> - threshMin = threshMax;
> - if (gopSize <= m_param->keyframeMin / 4)
> - bias = threshMin / 4;
> - else if (gopSize <= m_param->keyframeMin)
> - bias = threshMin * gopSize / m_param->keyframeMin;
> - else
> + double bias = 0.05;
> + if (bRealScenecut)
> {
> - bias = threshMin
> - + (threshMax - threshMin)
> - * (gopSize - m_param->keyframeMin)
> - / (m_param->keyframeMax - m_param->keyframeMin);
> + if (m_param->keyframeMin == m_param->keyframeMax)
> + threshMin = threshMax;
> + if (gopSize <= m_param->keyframeMin / 4)
> + bias = threshMin / 4;
> + else if (gopSize <= m_param->keyframeMin)
> + bias = threshMin * gopSize / m_param->keyframeMin;
> + else
> + {
> + bias = threshMin
> + + (threshMax - threshMin)
> + * (gopSize - m_param->keyframeMin)
> + / (m_param->keyframeMax - m_param->keyframeMin);
> + }
> }
> -
> bool res = pcost >= (1.0 - bias) * icost;
> if (res && bRealScenecut)
> {
> diff -r d56b2466c044 -r 51320561d41f source/encoder/slicetype.h
> --- a/source/encoder/slicetype.h Wed Aug 12 18:12:20 2015 +0530
> +++ 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
> @@ -156,7 +156,7 @@
> void slicetypeAnalyse(Lowres **frames, bool bKeyframe);
>
> /* called by slicetypeAnalyse() to make slice decisions */
> - bool scenecut(Lowres **frames, int p0, int p1, bool bRealScenecut, int numFrames, int maxSearch);
> + bool scenecut(Lowres **frames, int p0, int p1, bool bRealScenecut, int numFrames);
> bool scenecutInternal(Lowres **frames, int p0, int p1, bool bRealScenecut);
> void slicetypePath(Lowres **frames, int length, char(*best_paths)[X265_LOOKAHEAD_MAX + 1]);
> int64_t slicetypePathCost(Lowres **frames, char *path, int64_t threshold);
> _______________________________________________
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--
Steve Borho
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