<div><font size="2">Hi</font></div>
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<div><font size="2">I have tested echo cancellation using some different examples.</font></div>
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<div><font size="2">TEST 1. First, I record my voice, named TestVoice1. Then I perform testecho using TestVoice1 as the data of both mic and speaker. Final, I get a ideal result after modified the parameters for several times. It means the output is almost silent. I think this shows the echo cancellation can work.
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<div><font size="2">TEST 2. Then I edit the TestVoice1 using Audacity, add some other voice on it and generate TestVoice2. This time I use TestVoice2 as the data of mic, TestVoice1 as the data of speaker. The result is also very good.
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<div><font size="2">TEST 3. First, play TestVoice1, record it as TestVoice3. Then, I adjust the timeline of TestVoice3. So the position of sound from these two files are almost the same. This time I use TestVoice3 as the data of mic, TestVoice1 as the data of speaker. But the result is not good. After I compared the wave of TestVoice3 and the output found that them are almost the same, at least very similar.
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<div><font size="2">I wander if the non-linear distortion from the mic and speaker makes that result. Then I check spectrum of TestVoice1 and Testvoice3, and there isn't high distortion, I think.<font size="3"> </font>Can anyone give some advice? Thanks a lot!
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<div><font size="2">BTW, I use portaudio as audio driver.</font></div>