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1 /* | 1 /* |
2 * Copyright (C) 2011 Google Inc. All rights reserved. | 2 * Copyright (C) 2011 Google Inc. All rights reserved. |
3 * | 3 * |
4 * Redistribution and use in source and binary forms, with or without | 4 * Redistribution and use in source and binary forms, with or without |
5 * modification, are permitted provided that the following conditions | 5 * modification, are permitted provided that the following conditions |
6 * are met: | 6 * are met: |
7 * | 7 * |
8 * 1. Redistributions of source code must retain the above copyright | 8 * 1. Redistributions of source code must retain the above copyright |
9 * notice, this list of conditions and the following disclaimer. | 9 * notice, this list of conditions and the following disclaimer. |
10 * 2. Redistributions in binary form must reproduce the above copyright | 10 * 2. Redistributions in binary form must reproduce the above copyright |
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398 double eventFrame = event.time() * sampleRate; | 398 double eventFrame = event.time() * sampleRate; |
399 | 399 |
400 // Condition is currentFrame - 1 < eventFrame <= currentFrame, but c urrentFrame is | 400 // Condition is currentFrame - 1 < eventFrame <= currentFrame, but c urrentFrame is |
401 // unsigned and could be 0, so use currentFrame < eventFrame + 1 ins tead. | 401 // unsigned and could be 0, so use currentFrame < eventFrame + 1 ins tead. |
402 if (!((event.type() == ParamEvent::SetValue | 402 if (!((event.type() == ParamEvent::SetValue |
403 && (eventFrame <= currentFrame) | 403 && (eventFrame <= currentFrame) |
404 && (currentFrame < eventFrame + 1)))) | 404 && (currentFrame < eventFrame + 1)))) |
405 continue; | 405 continue; |
406 } | 406 } |
407 | 407 |
408 ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Typ e>(nextEvent->type()) : ParamEvent::LastType /* unknown */; | |
hongchan
2016/04/27 21:40:09
Are we okay with the comment style here? I've neve
Raymond Toy
2016/04/27 21:43:15
Don't know. I just basically moved this line up f
Raymond Toy
2016/04/27 22:57:03
It means a nextEventType equal to LastType indicat
| |
409 | |
410 // If the current event is SetTarget and the next event is a LinearRampT oValue or | |
411 // ExponentialRampToValue, special handling is needed. In this case, th e linear and | |
412 // exponential ramp should start at wherever the SetTarget processing ha s reached. | |
413 if (event.type() == ParamEvent::SetTarget | |
414 && (nextEventType == ParamEvent::LinearRampToValue | |
415 || nextEventType == ParamEvent::ExponentialRampToValue)) { | |
416 // Replace the SetTarget with a SetValue to set the starting time an d value for the ramp | |
417 // using the current frame and value. | |
418 m_events[i] = ParamEvent::createSetValueEvent(value, currentFrame / sampleRate); | |
419 } | |
420 | |
408 float value1 = event.value(); | 421 float value1 = event.value(); |
409 double time1 = event.time(); | 422 double time1 = event.time(); |
410 | 423 |
411 float value2 = nextEvent ? nextEvent->value() : value1; | 424 float value2 = nextEvent ? nextEvent->value() : value1; |
412 double time2 = nextEvent ? nextEvent->time() : endFrame / sampleRate + 1 ; | 425 double time2 = nextEvent ? nextEvent->time() : endFrame / sampleRate + 1 ; |
413 | 426 |
414 double deltaTime = time2 - time1; | 427 double deltaTime = time2 - time1; |
415 float k = deltaTime > 0 ? 1 / deltaTime : 0; | 428 float k = deltaTime > 0 ? 1 / deltaTime : 0; |
416 | 429 |
417 // |fillToEndFrame| is the exclusive upper bound of the last frame to be computed for this | 430 // |fillToEndFrame| is the exclusive upper bound of the last frame to be computed for this |
418 // event. It's either the last desired frame (|endFrame|) or derived fr om the end time of | 431 // event. It's either the last desired frame (|endFrame|) or derived fr om the end time of |
419 // the next event (time2). We compute ceil(time2*sampleRate) because fil lToEndFrame is the | 432 // the next event (time2). We compute ceil(time2*sampleRate) because fil lToEndFrame is the |
420 // exclusive upper bound. Consider the case where |startFrame| = 128 an d time2 = 128.1 | 433 // exclusive upper bound. Consider the case where |startFrame| = 128 an d time2 = 128.1 |
421 // (assuming sampleRate = 1). Since time2 is greater than 128, we want to output a value | 434 // (assuming sampleRate = 1). Since time2 is greater than 128, we want to output a value |
422 // for frame 128. This requires that fillToEndFrame be at least 129. T his is achieved by | 435 // for frame 128. This requires that fillToEndFrame be at least 129. T his is achieved by |
423 // ceil(time2). | 436 // ceil(time2). |
424 // | 437 // |
425 // However, time2 can be very large, so compute this carefully in the ca se where time2 | 438 // However, time2 can be very large, so compute this carefully in the ca se where time2 |
426 // exceeds the size of a size_t. | 439 // exceeds the size of a size_t. |
427 | 440 |
428 size_t fillToEndFrame = endFrame; | 441 size_t fillToEndFrame = endFrame; |
429 if (endFrame > time2 * sampleRate) | 442 if (endFrame > time2 * sampleRate) |
430 fillToEndFrame = static_cast<size_t>(ceil(time2 * sampleRate)); | 443 fillToEndFrame = static_cast<size_t>(ceil(time2 * sampleRate)); |
431 | 444 |
432 ASSERT(fillToEndFrame >= startFrame); | 445 ASSERT(fillToEndFrame >= startFrame); |
433 size_t fillToFrame = fillToEndFrame - startFrame; | 446 size_t fillToFrame = fillToEndFrame - startFrame; |
434 fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues)) ; | 447 fillToFrame = std::min(fillToFrame, static_cast<size_t>(numberOfValues)) ; |
435 | 448 |
436 ParamEvent::Type nextEventType = nextEvent ? static_cast<ParamEvent::Typ e>(nextEvent->type()) : ParamEvent::LastType /* unknown */; | |
437 | 449 |
438 // First handle linear and exponential ramps which require looking ahead to the next event. | 450 // First handle linear and exponential ramps which require looking ahead to the next event. |
439 if (nextEventType == ParamEvent::LinearRampToValue) { | 451 if (nextEventType == ParamEvent::LinearRampToValue) { |
440 const float valueDelta = value2 - value1; | 452 const float valueDelta = value2 - value1; |
441 #if CPU(X86) || CPU(X86_64) | 453 #if CPU(X86) || CPU(X86_64) |
442 // Minimize in-loop operations. Calculate starting value and increme nt. Next step: value += inc. | 454 // Minimize in-loop operations. Calculate starting value and increme nt. Next step: value += inc. |
443 // value = value1 + (currentFrame/sampleRate - time1) * k * (value2 - value1); | 455 // value = value1 + (currentFrame/sampleRate - time1) * k * (value2 - value1); |
444 // inc = 4 / sampleRate * k * (value2 - value1); | 456 // inc = 4 / sampleRate * k * (value2 - value1); |
445 // Resolve recursion by expanding constants to achieve a 4-step loop unrolling. | 457 // Resolve recursion by expanding constants to achieve a 4-step loop unrolling. |
446 // value = value1 + ((currentFrame/sampleRate - time1) + i * sample FrameTimeIncr) * k * (value2 -value1), i in 0..3 | 458 // value = value1 + ((currentFrame/sampleRate - time1) + i * sample FrameTimeIncr) * k * (value2 -value1), i in 0..3 |
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510 float multiplier = powf(value2 / value1, 1 / numSampleFrames); | 522 float multiplier = powf(value2 / value1, 1 / numSampleFrames); |
511 // Set the starting value of the exponential ramp. | 523 // Set the starting value of the exponential ramp. |
512 value = value1 * powf(value2 / value1, | 524 value = value1 * powf(value2 / value1, |
513 (currentFrame / sampleRate - time1) / deltaTime); | 525 (currentFrame / sampleRate - time1) / deltaTime); |
514 | 526 |
515 for (; writeIndex < fillToFrame; ++writeIndex) { | 527 for (; writeIndex < fillToFrame; ++writeIndex) { |
516 values[writeIndex] = value; | 528 values[writeIndex] = value; |
517 value *= multiplier; | 529 value *= multiplier; |
518 ++currentFrame; | 530 ++currentFrame; |
519 } | 531 } |
532 // Due to roundoff it's possible that value exceeds value2. Cli p value to value2 if | |
533 // we are within 1/2 frame of time2. | |
534 if (currentFrame > time2 * sampleRate - 0.5) | |
535 value = value2; | |
520 } | 536 } |
521 } else { | 537 } else { |
522 // Handle event types not requiring looking ahead to the next event. | 538 // Handle event types not requiring looking ahead to the next event. |
523 switch (event.type()) { | 539 switch (event.type()) { |
524 case ParamEvent::SetValue: | 540 case ParamEvent::SetValue: |
525 case ParamEvent::LinearRampToValue: | 541 case ParamEvent::LinearRampToValue: |
526 { | 542 { |
527 currentFrame = fillToEndFrame; | 543 currentFrame = fillToEndFrame; |
528 | 544 |
529 // Simply stay at a constant value. | 545 // Simply stay at a constant value. |
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771 // to the end of the values buffer. | 787 // to the end of the values buffer. |
772 for (; writeIndex < numberOfValues; ++writeIndex) | 788 for (; writeIndex < numberOfValues; ++writeIndex) |
773 values[writeIndex] = value; | 789 values[writeIndex] = value; |
774 | 790 |
775 // This value is used to set the .value attribute of the AudioParam. | 791 // This value is used to set the .value attribute of the AudioParam. |
776 return value; | 792 return value; |
777 } | 793 } |
778 | 794 |
779 } // namespace blink | 795 } // namespace blink |
780 | 796 |
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