[Freeswitch-users] KVM vs. XEN virtualization

[Stanislav Sinyagin]

I made additional tests by sending calls to sipgate.co.uk, and they confirm
my results: when sending a call from my Xen server in Switzerland, the
received audio is always perfect. But when sending from a Digitalocean host
in Amsterdam, I get the slipping frames.

I will re-test again during a business day, when the servers are likely to
be more busy.



On Sun, Apr 5, 2015 at 12:47 PM, Stanislav Sinyagin <ssinyagin at gmail.com>
wrote:

> Yrs, jitter buffer was enabled. Here I'm pretty sure that we deal with the
> clock skew.
> On Apr 5, 2015 12:07 PM, "Brian West" <brian at freeswitch.org> wrote:
>
>> 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>:
>>>
>>>> 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>
>>>> wrote:
>>>> > On Sat, Apr 4, 2015 at 1:03 PM, Regis M <
>>>> 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>:
>>>> >>>
>>>> >>> 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
>>>> >
>>>> >>> 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
>>>> >:
>>>> >>>>>
>>>> >>>>> 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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>>>
>>>
>>
>> --
>>
>> *Brian West*
>> brian at freeswitch.org
>>
>>
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