+1 sent from my mobile, Giovanni Maruzzelli cell: +39 347 266 56 18 On Apr 9, 2015 9:01 PM, "William King" <william.king@quentustech.com> wrote:
I'm surprised nobody has suggested doing point to point(FS to FS) within the same data center testing to remove the provider from the mix, then doing a packet capture on the receiving box. Wireshark will be able to determine the network jitter. Once you can determine and compensate for the level of RTP network jitter, then you can start looking for potential audio issues.
I've seen situations like you are describing, and they've all come down to the host machine was overloaded either at the CPU level, or the network stack.
William King Senior Engineer Quentus Technologies, INC 1037 NE 65th St Suite 273 Seattle, WA 98115 Main: (877) 211-9337 Office: (206) 388-4772 Cell: (253) 686-5518 william.king@quentustech.com
On 04/03/2015 05:16 PM, Stanislav Sinyagin wrote:
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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