VideoFrameScheduler.cpp revision c851b5de495169d7e9528644c2592746021bd968
1/* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17//#define LOG_NDEBUG 0 18#define LOG_TAG "VideoFrameScheduler" 19#include <utils/Log.h> 20#define ATRACE_TAG ATRACE_TAG_VIDEO 21#include <utils/Trace.h> 22 23#include <sys/time.h> 24 25#include <binder/IServiceManager.h> 26#include <gui/ISurfaceComposer.h> 27#include <ui/DisplayStatInfo.h> 28 29#include <media/stagefright/foundation/ADebug.h> 30 31#include "VideoFrameScheduler.h" 32 33namespace android { 34 35static const nsecs_t kNanosIn1s = 1000000000; 36 37template<class T> 38inline static const T divRound(const T &nom, const T &den) { 39 if ((nom >= 0) ^ (den >= 0)) { 40 return (nom - den / 2) / den; 41 } else { 42 return (nom + den / 2) / den; 43 } 44} 45 46template<class T> 47inline static T abs(const T &a) { 48 return a < 0 ? -a : a; 49} 50 51template<class T> 52inline static const T &min(const T &a, const T &b) { 53 return a < b ? a : b; 54} 55 56template<class T> 57inline static const T &max(const T &a, const T &b) { 58 return a > b ? a : b; 59} 60 61template<class T> 62inline static T periodicError(const T &val, const T &period) { 63 T err = abs(val) % period; 64 return (err < (period / 2)) ? err : (period - err); 65} 66 67template<class T> 68static int compare(const T *lhs, const T *rhs) { 69 if (*lhs < *rhs) { 70 return -1; 71 } else if (*lhs > *rhs) { 72 return 1; 73 } else { 74 return 0; 75 } 76} 77 78/* ======================================================================= */ 79/* PLL */ 80/* ======================================================================= */ 81 82static const size_t kMinSamplesToStartPrime = 3; 83static const size_t kMinSamplesToStopPrime = VideoFrameScheduler::kHistorySize; 84static const size_t kMinSamplesToEstimatePeriod = 3; 85static const size_t kMaxSamplesToEstimatePeriod = VideoFrameScheduler::kHistorySize; 86 87static const size_t kPrecision = 12; 88static const size_t kErrorThreshold = (1 << (kPrecision * 2)) / 10; 89static const int64_t kMultiplesThresholdDiv = 4; // 25% 90static const int64_t kReFitThresholdDiv = 100; // 1% 91static const nsecs_t kMaxAllowedFrameSkip = kNanosIn1s; // 1 sec 92static const nsecs_t kMinPeriod = kNanosIn1s / 120; // 120Hz 93static const nsecs_t kRefitRefreshPeriod = 10 * kNanosIn1s; // 10 sec 94 95VideoFrameScheduler::PLL::PLL() 96 : mPeriod(-1), 97 mPhase(0), 98 mPrimed(false), 99 mSamplesUsedForPriming(0), 100 mLastTime(-1), 101 mNumSamples(0) { 102} 103 104void VideoFrameScheduler::PLL::reset(float fps) { 105 //test(); 106 107 mSamplesUsedForPriming = 0; 108 mLastTime = -1; 109 110 // set up or reset video PLL 111 if (fps <= 0.f) { 112 mPeriod = -1; 113 mPrimed = false; 114 } else { 115 ALOGV("reset at %.1f fps", fps); 116 mPeriod = (nsecs_t)(1e9 / fps + 0.5); 117 mPrimed = true; 118 } 119 120 restart(); 121} 122 123// reset PLL but keep previous period estimate 124void VideoFrameScheduler::PLL::restart() { 125 mNumSamples = 0; 126 mPhase = -1; 127} 128 129#if 0 130 131void VideoFrameScheduler::PLL::test() { 132 nsecs_t period = kNanosIn1s / 60; 133 mTimes[0] = 0; 134 mTimes[1] = period; 135 mTimes[2] = period * 3; 136 mTimes[3] = period * 4; 137 mTimes[4] = period * 7; 138 mTimes[5] = period * 8; 139 mTimes[6] = period * 10; 140 mTimes[7] = period * 12; 141 mNumSamples = 8; 142 int64_t a, b, err; 143 fit(0, period * 12 / 7, 8, &a, &b, &err); 144 // a = 0.8(5)+ 145 // b = -0.14097(2)+ 146 // err = 0.2750578(703)+ 147 ALOGD("a=%lld (%.6f), b=%lld (%.6f), err=%lld (%.6f)", 148 (long long)a, (a / (float)(1 << kPrecision)), 149 (long long)b, (b / (float)(1 << kPrecision)), 150 (long long)err, (err / (float)(1 << (kPrecision * 2)))); 151} 152 153#endif 154 155void VideoFrameScheduler::PLL::fit( 156 nsecs_t phase, nsecs_t period, size_t numSamplesToUse, 157 int64_t *a, int64_t *b, int64_t *err) { 158 if (numSamplesToUse > mNumSamples) { 159 numSamplesToUse = mNumSamples; 160 } 161 162 int64_t sumX = 0; 163 int64_t sumXX = 0; 164 int64_t sumXY = 0; 165 int64_t sumYY = 0; 166 int64_t sumY = 0; 167 168 int64_t x = 0; // x usually is in [0..numSamplesToUse) 169 nsecs_t lastTime; 170 for (size_t i = 0; i < numSamplesToUse; i++) { 171 size_t ix = (mNumSamples - numSamplesToUse + i) % kHistorySize; 172 nsecs_t time = mTimes[ix]; 173 if (i > 0) { 174 x += divRound(time - lastTime, period); 175 } 176 // y is usually in [-numSamplesToUse..numSamplesToUse+kRefitRefreshPeriod/kMinPeriod) << kPrecision 177 // ideally in [0..numSamplesToUse), but shifted by -numSamplesToUse during 178 // priming, and possibly shifted by up to kRefitRefreshPeriod/kMinPeriod 179 // while we are not refitting. 180 int64_t y = divRound(time - phase, period >> kPrecision); 181 sumX += x; 182 sumY += y; 183 sumXX += x * x; 184 sumXY += x * y; 185 sumYY += y * y; 186 lastTime = time; 187 } 188 189 int64_t div = numSamplesToUse * sumXX - sumX * sumX; 190 int64_t a_nom = numSamplesToUse * sumXY - sumX * sumY; 191 int64_t b_nom = sumXX * sumY - sumX * sumXY; 192 *a = divRound(a_nom, div); 193 *b = divRound(b_nom, div); 194 // don't use a and b directly as the rounding error is significant 195 *err = sumYY - divRound(a_nom * sumXY + b_nom * sumY, div); 196 ALOGV("fitting[%zu] a=%lld (%.6f), b=%lld (%.6f), err=%lld (%.6f)", 197 numSamplesToUse, 198 (long long)*a, (*a / (float)(1 << kPrecision)), 199 (long long)*b, (*b / (float)(1 << kPrecision)), 200 (long long)*err, (*err / (float)(1 << (kPrecision * 2)))); 201} 202 203void VideoFrameScheduler::PLL::prime(size_t numSamplesToUse) { 204 if (numSamplesToUse > mNumSamples) { 205 numSamplesToUse = mNumSamples; 206 } 207 CHECK(numSamplesToUse >= 3); // must have at least 3 samples 208 209 // estimate video framerate from deltas between timestamps, and 210 // 2nd order deltas 211 Vector<nsecs_t> deltas; 212 nsecs_t lastTime, firstTime; 213 for (size_t i = 0; i < numSamplesToUse; ++i) { 214 size_t index = (mNumSamples - numSamplesToUse + i) % kHistorySize; 215 nsecs_t time = mTimes[index]; 216 if (i > 0) { 217 if (time - lastTime > kMinPeriod) { 218 //ALOGV("delta: %lld", (long long)(time - lastTime)); 219 deltas.push(time - lastTime); 220 } 221 } else { 222 firstTime = time; 223 } 224 lastTime = time; 225 } 226 deltas.sort(compare<nsecs_t>); 227 size_t numDeltas = deltas.size(); 228 if (numDeltas > 1) { 229 nsecs_t deltaMinLimit = min(deltas[0] / kMultiplesThresholdDiv, kMinPeriod); 230 nsecs_t deltaMaxLimit = deltas[numDeltas / 2] * kMultiplesThresholdDiv; 231 for (size_t i = numDeltas / 2 + 1; i < numDeltas; ++i) { 232 if (deltas[i] > deltaMaxLimit) { 233 deltas.resize(i); 234 numDeltas = i; 235 break; 236 } 237 } 238 for (size_t i = 1; i < numDeltas; ++i) { 239 nsecs_t delta2nd = deltas[i] - deltas[i - 1]; 240 if (delta2nd >= deltaMinLimit) { 241 //ALOGV("delta2: %lld", (long long)(delta2nd)); 242 deltas.push(delta2nd); 243 } 244 } 245 } 246 247 // use the one that yields the best match 248 int64_t bestScore; 249 for (size_t i = 0; i < deltas.size(); ++i) { 250 nsecs_t delta = deltas[i]; 251 int64_t score = 0; 252#if 1 253 // simplest score: number of deltas that are near multiples 254 size_t matches = 0; 255 for (size_t j = 0; j < deltas.size(); ++j) { 256 nsecs_t err = periodicError(deltas[j], delta); 257 if (err < delta / kMultiplesThresholdDiv) { 258 ++matches; 259 } 260 } 261 score = matches; 262#if 0 263 // could be weighed by the (1 - normalized error) 264 if (numSamplesToUse >= kMinSamplesToEstimatePeriod) { 265 int64_t a, b, err; 266 fit(firstTime, delta, numSamplesToUse, &a, &b, &err); 267 err = (1 << (2 * kPrecision)) - err; 268 score *= max(0, err); 269 } 270#endif 271#else 272 // or use the error as a negative score 273 if (numSamplesToUse >= kMinSamplesToEstimatePeriod) { 274 int64_t a, b, err; 275 fit(firstTime, delta, numSamplesToUse, &a, &b, &err); 276 score = -delta * err; 277 } 278#endif 279 if (i == 0 || score > bestScore) { 280 bestScore = score; 281 mPeriod = delta; 282 mPhase = firstTime; 283 } 284 } 285 ALOGV("priming[%zu] phase:%lld period:%lld", numSamplesToUse, mPhase, mPeriod); 286} 287 288nsecs_t VideoFrameScheduler::PLL::addSample(nsecs_t time) { 289 if (mLastTime >= 0 290 // if time goes backward, or we skipped rendering 291 && (time > mLastTime + kMaxAllowedFrameSkip || time < mLastTime)) { 292 restart(); 293 } 294 295 mLastTime = time; 296 mTimes[mNumSamples % kHistorySize] = time; 297 ++mNumSamples; 298 299 bool doFit = time > mRefitAt; 300 if ((mPeriod <= 0 || !mPrimed) && mNumSamples >= kMinSamplesToStartPrime) { 301 prime(kMinSamplesToStopPrime); 302 ++mSamplesUsedForPriming; 303 doFit = true; 304 } 305 if (mPeriod > 0 && mNumSamples >= kMinSamplesToEstimatePeriod) { 306 if (mPhase < 0) { 307 // initialize phase to the current render time 308 mPhase = time; 309 doFit = true; 310 } else if (!doFit) { 311 int64_t err = periodicError(time - mPhase, mPeriod); 312 doFit = err > mPeriod / kReFitThresholdDiv; 313 } 314 315 if (doFit) { 316 int64_t a, b, err; 317 mRefitAt = time + kRefitRefreshPeriod; 318 fit(mPhase, mPeriod, kMaxSamplesToEstimatePeriod, &a, &b, &err); 319 mPhase += (mPeriod * b) >> kPrecision; 320 mPeriod = (mPeriod * a) >> kPrecision; 321 ALOGV("new phase:%lld period:%lld", (long long)mPhase, (long long)mPeriod); 322 323 if (err < kErrorThreshold) { 324 if (!mPrimed && mSamplesUsedForPriming >= kMinSamplesToStopPrime) { 325 mPrimed = true; 326 } 327 } else { 328 mPrimed = false; 329 mSamplesUsedForPriming = 0; 330 } 331 } 332 } 333 return mPeriod; 334} 335 336/* ======================================================================= */ 337/* Frame Scheduler */ 338/* ======================================================================= */ 339 340static const nsecs_t kDefaultVsyncPeriod = kNanosIn1s / 60; // 60Hz 341static const nsecs_t kVsyncRefreshPeriod = kNanosIn1s; // 1 sec 342 343VideoFrameScheduler::VideoFrameScheduler() 344 : mVsyncTime(0), 345 mVsyncPeriod(0), 346 mVsyncRefreshAt(0), 347 mLastVsyncTime(-1), 348 mTimeCorrection(0) { 349} 350 351void VideoFrameScheduler::updateVsync() { 352 mVsyncRefreshAt = systemTime(SYSTEM_TIME_MONOTONIC) + kVsyncRefreshPeriod; 353 mVsyncPeriod = 0; 354 mVsyncTime = 0; 355 356 // TODO: schedule frames for the destination surface 357 // For now, surface flinger only schedules frames on the primary display 358 if (mComposer == NULL) { 359 String16 name("SurfaceFlinger"); 360 sp<IServiceManager> sm = defaultServiceManager(); 361 mComposer = interface_cast<ISurfaceComposer>(sm->checkService(name)); 362 } 363 if (mComposer != NULL) { 364 DisplayStatInfo stats; 365 status_t res = mComposer->getDisplayStats(NULL /* display */, &stats); 366 if (res == OK) { 367 ALOGV("vsync time:%lld period:%lld", 368 (long long)stats.vsyncTime, (long long)stats.vsyncPeriod); 369 mVsyncTime = stats.vsyncTime; 370 mVsyncPeriod = stats.vsyncPeriod; 371 } else { 372 ALOGW("getDisplayStats returned %d", res); 373 } 374 } else { 375 ALOGW("could not get surface mComposer service"); 376 } 377} 378 379void VideoFrameScheduler::init(float videoFps) { 380 updateVsync(); 381 382 mLastVsyncTime = -1; 383 mTimeCorrection = 0; 384 385 mPll.reset(videoFps); 386} 387 388void VideoFrameScheduler::restart() { 389 mLastVsyncTime = -1; 390 mTimeCorrection = 0; 391 392 mPll.restart(); 393} 394 395nsecs_t VideoFrameScheduler::getVsyncPeriod() { 396 if (mVsyncPeriod > 0) { 397 return mVsyncPeriod; 398 } 399 return kDefaultVsyncPeriod; 400} 401 402nsecs_t VideoFrameScheduler::schedule(nsecs_t renderTime) { 403 nsecs_t origRenderTime = renderTime; 404 405 nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC); 406 if (now >= mVsyncRefreshAt) { 407 updateVsync(); 408 } 409 410 // without VSYNC info, there is nothing to do 411 if (mVsyncPeriod == 0) { 412 ALOGV("no vsync: render=%lld", (long long)renderTime); 413 return renderTime; 414 } 415 416 // ensure vsync time is well before (corrected) render time 417 if (mVsyncTime > renderTime - 4 * mVsyncPeriod) { 418 mVsyncTime -= 419 ((mVsyncTime - renderTime) / mVsyncPeriod + 5) * mVsyncPeriod; 420 } 421 422 // Video presentation takes place at the VSYNC _after_ renderTime. Adjust renderTime 423 // so this effectively becomes a rounding operation (to the _closest_ VSYNC.) 424 renderTime -= mVsyncPeriod / 2; 425 426 const nsecs_t videoPeriod = mPll.addSample(origRenderTime); 427 if (videoPeriod > 0) { 428 // Smooth out rendering 429 size_t N = 12; 430 nsecs_t fiveSixthDev = 431 abs(((videoPeriod * 5 + mVsyncPeriod) % (mVsyncPeriod * 6)) - mVsyncPeriod) 432 / (mVsyncPeriod / 100); 433 // use 20 samples if we are doing 5:6 ratio +- 1% (e.g. playing 50Hz on 60Hz) 434 if (fiveSixthDev < 12) { /* 12% / 6 = 2% */ 435 N = 20; 436 } 437 438 nsecs_t offset = 0; 439 nsecs_t edgeRemainder = 0; 440 for (size_t i = 1; i <= N; i++) { 441 offset += 442 (renderTime + mTimeCorrection + videoPeriod * i - mVsyncTime) % mVsyncPeriod; 443 edgeRemainder += (videoPeriod * i) % mVsyncPeriod; 444 } 445 mTimeCorrection += mVsyncPeriod / 2 - offset / N; 446 renderTime += mTimeCorrection; 447 nsecs_t correctionLimit = mVsyncPeriod * 3 / 5; 448 edgeRemainder = abs(edgeRemainder / N - mVsyncPeriod / 2); 449 if (edgeRemainder <= mVsyncPeriod / 3) { 450 correctionLimit /= 2; 451 } 452 453 // estimate how many VSYNCs a frame will spend on the display 454 nsecs_t nextVsyncTime = 455 renderTime + mVsyncPeriod - ((renderTime - mVsyncTime) % mVsyncPeriod); 456 if (mLastVsyncTime >= 0) { 457 size_t minVsyncsPerFrame = videoPeriod / mVsyncPeriod; 458 size_t vsyncsForLastFrame = divRound(nextVsyncTime - mLastVsyncTime, mVsyncPeriod); 459 bool vsyncsPerFrameAreNearlyConstant = 460 periodicError(videoPeriod, mVsyncPeriod) / (mVsyncPeriod / 20) == 0; 461 462 if (mTimeCorrection > correctionLimit && 463 (vsyncsPerFrameAreNearlyConstant || vsyncsForLastFrame > minVsyncsPerFrame)) { 464 // remove a VSYNC 465 mTimeCorrection -= mVsyncPeriod / 2; 466 renderTime -= mVsyncPeriod / 2; 467 nextVsyncTime -= mVsyncPeriod; 468 --vsyncsForLastFrame; 469 } else if (mTimeCorrection < -correctionLimit && 470 (vsyncsPerFrameAreNearlyConstant || vsyncsForLastFrame == minVsyncsPerFrame)) { 471 // add a VSYNC 472 mTimeCorrection += mVsyncPeriod / 2; 473 renderTime += mVsyncPeriod / 2; 474 nextVsyncTime += mVsyncPeriod; 475 ++vsyncsForLastFrame; 476 } 477 ATRACE_INT("FRAME_VSYNCS", vsyncsForLastFrame); 478 } 479 mLastVsyncTime = nextVsyncTime; 480 } 481 482 // align rendertime to the center between VSYNC edges 483 renderTime -= (renderTime - mVsyncTime) % mVsyncPeriod; 484 renderTime += mVsyncPeriod / 2; 485 ALOGV("adjusting render: %lld => %lld", (long long)origRenderTime, (long long)renderTime); 486 ATRACE_INT("FRAME_FLIP_IN(ms)", (renderTime - now) / 1000000); 487 return renderTime; 488} 489 490void VideoFrameScheduler::release() { 491 mComposer.clear(); 492} 493 494VideoFrameScheduler::~VideoFrameScheduler() { 495 release(); 496} 497 498} // namespace android 499 500