Frame rate detection on MotionMark occasionally sees older devices as 90 fps instead of 60 #50
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shallawa
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… 90 fps instead of 60 WebKit#50 rdar://127012351 To get the target frame rate we sample 300 rAFs and we get the average of their frame rates. We calculate the average incrementally using some sort of exponential decay. The average starts very small but keeps increasing until it reaches the actual target frame rate and it is supposed to stay unchanged much. Then we compare the final average rate with predefined frame rates and get the closest one. The purpose of this incremental calculation was to show the target frame rate being calculated in the detectionProgressElement in the developer page. In addition to having the incremental average very small for more than 100 frames, the bigger problem is this incremental average calculation gives more weight to the last frame. And if it is considerably large for any reason, the final average will be wildly inaccurate. The fix is to simplify the calculations: 1. For count == 0: The firstTimeStamp will be recorded and and we won't update the detectionProgressElement. 2. For count > 0: averageFrameLength = (timestamp - firstTimeStamp) / count; averageFrameRate = 1000 / averageFrameLength;
shallawa
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Apr 25, 2024
… 90 fps instead of 60 WebKit#50 rdar://127012351 To get the target frame rate we sample 300 rAFs and we get the average of their frame rates. We calculate the average incrementally using some sort of exponential decay. The average starts very small but keeps increasing until it reaches the actual target frame rate and it is supposed to stay unchanged much. Then we compare the final average rate with predefined frame rates and get the closest one. The purpose of this incremental calculation was to show the target frame rate being calculated in the detectionProgressElement in the developer page. In addition to having the incremental average very small for more than 100 frames, the bigger problem is this incremental average calculation gives more weight to the last frame. And if it is considerably large for any reason, the final average will be wildly inaccurate. The fix is to simplify the calculations: 1. For count == 0: The firstTimeStamp will be recorded and and we won't update the detectionProgressElement. 2. For count > 0: averageFrameLength = (timestamp - firstTimeStamp) / count; averageFrameRate = 1000 / averageFrameLength;
smfr
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Apr 25, 2024
… 90 fps instead of 60 #50 rdar://127012351 To get the target frame rate we sample 300 rAFs and we get the average of their frame rates. We calculate the average incrementally using some sort of exponential decay. The average starts very small but keeps increasing until it reaches the actual target frame rate and it is supposed to stay unchanged much. Then we compare the final average rate with predefined frame rates and get the closest one. The purpose of this incremental calculation was to show the target frame rate being calculated in the detectionProgressElement in the developer page. In addition to having the incremental average very small for more than 100 frames, the bigger problem is this incremental average calculation gives more weight to the last frame. And if it is considerably large for any reason, the final average will be wildly inaccurate. The fix is to simplify the calculations: 1. For count == 0: The firstTimeStamp will be recorded and and we won't update the detectionProgressElement. 2. For count > 0: averageFrameLength = (timestamp - firstTimeStamp) / count; averageFrameRate = 1000 / averageFrameLength;
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The incremental frame rate average calculation gives much more weight to the last frame. So sometimes it can be wildly inaccurate. And this makes it pick the wrong predefined frame rate.
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