[Speex-dev] Notch Filter in AEC

[QianBin]

Hi,

    But in fact, it really affects the voice quality. One of my tester says, "Is your mouth far way from the mic?"
    Could you explain why we should cut 200hz below?

>The notch filter is specifically designed to cut below 200 Hz when 
>working in narrowband. In wideband, the cutoff is more around 50 Hz. The 
>reason is that in narrowband operation (irrespective of the codec), 
>you're not really supposed to have anything below ~200 Hz, but a lot of 
>people forget that.
>
>	Jean-Marc
>
>On 2010-03-03 02:40, brant wrote:
>> Hi,
>>
>>     The notch filter in AEC is only used to remove DC signal, and the time of convergence is not important, right?
>> If so, I think preset value of notch_radius is too small, and it causes noticeable distortion(freq<  200hz cut).
>> There is a picture in attachment to show signals under different radius in time-domain.
>>    By setting notch_radius to 0.999 for all sampling rates, I found better voice effect(distortion), while AEC still
>> working fine.
>>
>>
>> 	
>>
>> 　　　　　　　　QinBin
>> 　　　　　　　　cola_tin at 163.com
>> 　　　　　　　　　　2010-03-03
>>
>>
>>
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　　　　　　　　QianBin
　　　　　　　　cola_tin at 163.com
　　　　　　　　　　2010-03-03