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> Add an extended filter mode to AEC. > > This mode extends the filter length from the current 48 ms to 128 ms. > It is runtime selectable which allows it to be enabled through > experiment. We reuse the DelayCorrection infrastructure to avoid having > to replumb everything up to libjingle. > > Increases AEC complexity by ~50% on modern x86 CPUs. > Measurements (in percent of usage on one core): > > Machine/CPU Normal Extended > MacBook Retina (Early 2013), > Core i7 Ivy Bridge (2.7 GHz, hyperthreaded) 0.6% 0.9% > > MacBook Air (Late 2010), Core 2 Duo (2.13 GHz) 1.4% 2.7% > > Chromebook Pixel, Core i5 Ivy Bridge (1.8 GHz) 0.6% 1.0% > > Samsung ARM Chromebook, > Samsung Exynos 5 Dual (1.7 GHz) 3.2% 5.6% > > The relative value is large of course but the absolute should be > acceptable in order to have a working AEC on some platforms. > > Detailed changes to the algorithm: > - The filter length is changed from 48 to 128 ms. This comes with tuning > of several parameters: i) filter adaptation stepsize and error > threshold; ii) non-linear processing smoothing and overdrive. > - Option to ignore the reported delays on platforms which we deem > sufficiently unreliable. Currently this will be enabled in Chromium for > Mac. > - Faster startup times by removing the excessive "startup phase" > processing of reported delays. > - Much more conservative adjustments to the far-end read pointer. We > smooth the delay difference more heavily, and back off from the > difference more. Adjustments force a readaptation of the filter, so they > should be avoided except when really necessary. > > Corresponds to these changes: > https://chromereviews.googleplex.com/9412014 > https://chromereviews.googleplex.com/9514013 > https://chromereviews.googleplex.com/9960013 > > BUG=454,827,1261 > R=bjornv@webrtc.org > > Review URL: https://webrtc-codereview.appspot.com/2151007 TBR=andrew@webrtc.org Review URL: https://webrtc-codereview.appspot.com/2296005 git-svn-id: http://webrtc.googlecode.com/svn/trunk@4839 4adac7df-926f-26a2-2b94-8c16560cd09d