A standard deviation of 0.3 milliseconds is consistent with a position counter that has a granularity of 1 millisecond, which is too coarse. Your position counter should have a granularity of 1 sample. From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Gaurav Khuntale Sent: Tuesday, April 29, 2014 8:59 AM To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Need help in Passing a test case from KS-Position test Hello, I am working on a virtual audio driver which is based on wave cyclic port driver. The driver similar to the MSVAD sample driver from the DDK. I am facing an issue with understanding a test from KS position test. Following are the extracts from the test log: Collected 6857 good data points which covers 80828.491 ms Detected 0 glitches in 81 seconds Specified sample rate = 176400.000 bytes/sec, 44100.000 samples/sec Calculated sample rate = 176400.004 bytes/sec, 44100.001 samples/sec Sample rate drifting ratio = 0.000002 % Average position noise magnitude = 0.279960 ms STD of position noise = 0.332027 ms 0.247922% of position noise is larger than 0.8 ms Largest short term (2 seconds) position noise average is 0.000547ms FAIL: STD of position noise is 0.332027ms which is larger than 0.3ms End Case: ID 16.26:1.8 : FAIL : Standard Streaming\Rendering Performance Tests\Position Drift and Jitter for AEC : [Mon Apr 28 15:50:02 2014] The GetPosition() implementation is similar to the one in MSVAD. I am not getting what the test wants to say and what it is expecting. So can anyone please explain it to me? Thanks.