[asterisk-users] Dahdi_dummy is more accurate than core timer?

[Johan Wilfer]

2013-10-02 13:55, Gareth Blades skrev:
> On 02/10/13 12:17, Johan Wilfer wrote:
>> Hi,
>>
>> I have some servers that are dedicated to do meetme conferencing. From
>> some previous test i concluded that I need to use dahdi_dummy as it is
>> more accurate.
>>
>> If I did use the core timers in dahdi (not loading dahdi_dummy) I got
>> bad quality in the conferences and dahdi_test showed 99.6% as worst.
>>
>> I thought maybe the issue as bad hardware for the timing or something
>> else. But today I re-ran these tests on another server showing the
>> same thing.
>>
>> - Can anybody comment on why DAHDI with core timers drop down to 99.6%
>> occasionally?
>> - Is a hardware-card for timing the most efficient way to get timing
>> even if I just use the card for the timing?
>>
>>
>
> Its a little different when you are using meetme as its an application
> built into dahdi itself and not a native asterisk application. It will
> therefore always use dahdi for its timing. If dahdi doesnt have a
> hardware interface (sangoma sell a usb based timing source if you want a
> hardware source) then it will use a software timing source of some form.
> I dont know what method it uses.

Yes, this is for a legacy application that are using Meetme. Maybe I was 
unclear above but with "core timer" I meant just "modprobe dahdi".
"dahdi_dummy" = "modprobe dahdi_dummy" and the hw card used "wct4xxp".

> More information about timing sources can be found at :-
> https://wiki.asterisk.org/wiki/display/AST/Timing+Interfaces

The wiki states:

"As of DAHDI Linux 2.3.0 the dahdi_dummy module has been removed and its 
functionality moved into the main dahdi kernel module. As long as the 
dahdi module is loaded, it will provide timing to Asterisk either 
through installed telephony hardware or utilizing the kernel timing 
facilities when separate hardware is not available."

But when I test just dahdi (core timer, no dahdi_dummy) I get distortion 
and bad quality in the Meetme-conferences. This does not happen with 
dahdi_dummy.


-- 
Johan Wilfer