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 -------------- next part -------------- A non-text attachment was scrubbed... Name: notch.jpg Type: image/jpeg Size: 47929 bytes Desc: not available Url : http://lists.xiph.org/pipermail/speex-dev/attachments/20100303/11c19fe1/attachment-0001.jpg
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 > > > > _______________________________________________ > Speex-dev mailing list > Speex-dev at xiph.org > http://lists.xiph.org/mailman/listinfo/speex-dev
Hi Jean-Marc,
You make that sound like its just a matter of meeting some arbitrary
spec. Let's be more specific.....
If you use narrow band voice down to deep bass frequencies:
- 16 bit linear audio sounds good
- alaw or ulaw sounds muddy
- low bit rate codecs, like speex or G.729, sound awful.
I assume QinBin only listened to some uncompressed audio in his evaluation.
Steve
On 03/03/2010 07:39 PM, Jean-Marc Valin wrote:> 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.
>>
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
>>
>>
>>
>> _______________________________________________
>> Speex-dev mailing list
>> Speex-dev at xiph.org
>> http://lists.xiph.org/mailman/listinfo/speex-dev
= = = = = = = = = = = = = = = = = = =
????????QianBin
????????cola_tin at 163.com
??????????2010-03-03