Improved visual quality with 3x times speed-up.
Change list:
1. Remove second chance filter in temporal denoising filter to mitigate trailing artifact.
2. Add swap buffer to save one whole-frame memcpy.
3. Do noise estimation on every N blocks.
4. Adopt a faster moving object detection algorithm (change the structure).
5. Refactor the for loops and PositionCheck().
6. Refactor the function ReduceFalseDetection (RFD).
7. Fix a bug in TrailingBlock() which causes a mismatch.
8. Change unit test to support swap buffer test.
9. Remove CopyMem8x8, use memcpy to copy U/V plane which can be optimized future.
10. Remove DenoiseMetrics.
Review URL: https://codereview.webrtc.org/1871853003
Cr-Commit-Position: refs/heads/master@{#12340}
Improved the existing external denoiser in WebRTC: the filter strength
is adaptive based on the noise level of the whole frame and the moving
object detection result. The adaptive filter effectively removes the
artifacts in previous version, such as trailing and blockiness on moving
objects.
The external denoiser is off by default for now.
BUG=
Review URL: https://codereview.webrtc.org/1822333003
Cr-Commit-Position: refs/heads/master@{#12198}
