[x265] [PATCH 1 of 2] slicetype: Modify Scenecut algorithm to detect scene transition points
aarthi at multicorewareinc.com
aarthi at multicorewareinc.com
Mon Aug 17 07:41:41 CEST 2015
# 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.
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;
+ }
+ break;
+ }
+ }
+ if (frames[i]->bScenecut)
+ {
+ frames[i]->bScenecut = false;
+ }
+ }
+ }
+ 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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