[pjsip] 256 samples per frame

nir elkayam nir.elkayam at gmail.com
Mon Dec 14 10:34:54 EST 2009


hi,

my mistake, it can handle 160 as 160 = 2*2*2*2*2*5 and there is the fft-5
there.

from what i have seen, it actually uses fft of length double then the frame
length so u might want to reduce it to 128, but that might be to low.

On Mon, Dec 14, 2009 at 5:16 PM, nir elkayam <nir.elkayam at gmail.com> wrote:

> hi,
>
> try to look into the code and see whether the speex AEC uses FFT 0f 160 or
> 256.
> I am not sure it will use 160 because it is less effective then 256.
> if u could point to the correct place in the code that would be great.
>
> nir
>
>
> On Mon, Dec 14, 2009 at 5:07 PM, Benny Prijono <bennylp at teluu.com> wrote:
>
>> On Fri, Dec 11, 2009 at 5:52 PM, fabio cherchi <fabio.cherchi at yahoo.it>
>> wrote:
>> > Hello,
>> >
>> > my question is very simple.
>> > I realized a hardware version of the kiss fft for the AEC Speex in the
>> > pjsip.
>> > It can handle 256 samples per frame while the whole application (and
>> audio
>> > driver) actually is working with 160 samples per frame.
>> >
>> > I'm evaluating 2 options:
>> >
>> > 1) to keep the 160 samples per frame and use the zero-padding technique
>> to
>> > fill the remaining empty frame.
>> > Question: does anybody know what's the effect of the zero-padding in the
>> > inverse fft?
>> >
>>
>> I'm no FFT master, but I don't think the effect is good!
>>
>> > 2) to scale up all the system to handle 256 samples per frame.
>> > Question: is the pjmedia suitable for 256 samples per frame instead of
>> 160?
>> >
>>
>> That should be okay, just open both the sound device and the
>> conference bridge to use 256 samples per frame, and let anything else
>> unchanged. The conference bridge would automatically do the buffering
>> for any ports connected to it, if they use different samples per frame
>> setting.
>>
>> Though the drawback is of course there will be more memmove()
>> operations involved.
>>
>> Cheers
>>  benny
>>
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>>
>
>
>
> --
> ניר אלקיים
> טל: 050-3930056
> nir.elkayam at gmail.com
>
>


-- 
ניר אלקיים
טל: 050-3930056
nir.elkayam at gmail.com
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