[Freeswitch-users] KVM vs. XEN virtualization

Sun Apr 5 14:06:03 MSD 2015

Correct me if I'm wrong but is sounds like you've described jitter.  Did
you test with the jitter buffer enabled?

On Sunday, April 5, 2015, Regis M <regis.freeswitch.org at tornad.net> wrote:

> nice work !!!  Thanks for sharing.
>
>
>
> 2015-04-05 2:37 GMT+02:00 Stanislav Sinyagin <ssinyagin at gmail.com
> <javascript:_e(%7B%7D,'cvml','ssinyagin at gmail.com');>>:
>
>> here we go:
>>
>> https://txlab.wordpress.com/2015/04/05/testing-rtp-clock-precision-on-a-virtual-machine/
>>
>>
>>
>> On Sat, Apr 4, 2015 at 4:26 PM, Stanislav Sinyagin <ssinyagin at gmail.com
>> <javascript:_e(%7B%7D,'cvml','ssinyagin at gmail.com');>> wrote:
>> > On Sat, Apr 4, 2015 at 1:03 PM, Regis M <
>> regis.freeswitch.org at tornad.net
>> <javascript:_e(%7B%7D,'cvml','regis.freeswitch.org at tornad.net');>> wrote:
>> >> How do you check wavs together in audacity ?
>> >
>> > you just open two WAV files, align their starting position, and
>> > visually check the waves. If there's a problem, you would see that
>> > after few seconds, the waves are not aligned any more.
>> >
>> >> Can you send me 2 samples wav (send... and recorded) so I could see
>> the 20ms
>> >> diff that you exposed...
>> >>
>> >> Is there a way to automate the result checking, so it could help to
>> monitor
>> >> itsp quality
>> >
>> > Here
>> > https://github.com/openpreserve/scape-xcorrsound/issues/17
>> > this is a link to a tool which compares two sound files at the wave
>> > level. You can also see the sound samples in the ticket.
>> > The problem is, that currently this tool does not detect such slipping
>> frames.
>> >
>> > I will also write a detailed article with examples, during the weekend.
>> >
>> >
>> >
>> >
>> >
>> >>
>> >>
>> >> 2015-04-04 12:53 GMT+02:00 Stanislav Sinyagin <ssinyagin at gmail.com
>> <javascript:_e(%7B%7D,'cvml','ssinyagin at gmail.com');>>:
>> >>>
>> >>> Important is to send the media through two independent carriers -
>> then you
>> >>> can be sure that your clock is compared against a high quality one.
>> >>>
>> >>> On Apr 4, 2015 12:46 PM, "Regis M" <regis.freeswitch.org at tornad.net
>> <javascript:_e(%7B%7D,'cvml','regis.freeswitch.org at tornad.net');>>
>> >>> wrote:
>> >>>>
>> >>>> Hi,
>> >>>>
>> >>>> It's a very interresting test and conclusion.
>> >>>>
>> >>>> I will try to build a similar environnement on my freeswitch to check
>> >>>> some system :)
>> >>>>
>> >>>> thanks
>> >>>>
>> >>>>
>> >>>>
>> >>>> 2015-04-04 2:16 GMT+02:00 Stanislav Sinyagin <ssinyagin at gmail.com
>> <javascript:_e(%7B%7D,'cvml','ssinyagin at gmail.com');>>:
>> >>>>>
>> >>>>> hi,
>> >>>>>
>> >>>>> Here are some test results which might be interesting:
>> >>>>>
>> >>>>> I've set up a test FreeSWITCH server at digitalocean (they use KVM),
>> >>>>> and originated test calls to some ITSP accounts. Each call played a
>> >>>>> test sound file (voice samples from ITU:
>> >>>>>
>> http://www.itu.int/net/itu-t/sigdb/genaudio/AudioForm-g.aspx?val=1000050
>> >>>>> ), and on the receiving end another FreeSWITCH server was recording
>> >>>>> the received session. The receiving server was on a XEN VM. Both
>> >>>>> servers talked G711 to their corresponding ITSP accounts.
>> >>>>>
>> >>>>> Then I compared the source audio and received audio in Audacity
>> editor.
>> >>>>>
>> >>>>> The tests showed that the received voice wave shifts 20ms from the
>> >>>>> original sound every few seconds, randomly back and forward. This
>> >>>>> skewing was always present, regardless of ITSP and time of day.
>> >>>>>
>> >>>>> Then I moved the sending server to a XEN VM, and the waves appeared
>> >>>>> almost perfectly synchronized (there was a 5ms skew in one test,
>> and I
>> >>>>> guess it's related to transcoding buffer, as the sound was obviously
>> >>>>> transcoded).
>> >>>>>
>> >>>>> The effect was always visible with a 30-second sample, and I also
>> made
>> >>>>> additional tests with 2-minute samples.
>> >>>>>
>> >>>>> It would also be interesting to test this from a VmWare VM. If
>> someone
>> >>>>> wants to run such a test, feel free to contact me directly.
>> >>>>>
>> >>>>>
>> >>>>> cheers,
>> >>>>> stan
>> >>>>>
>> >>>>>
>> >>>>>
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>
>

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