[Asterisk-Users] TDM users: modified zttest.c for testing

[Roger Gulbranson]

On Tue, 2005-05-03 at 09:48 -0600, Rich Adamson wrote:
> TDM & X100P card users:
> 
> Attached is a modified zaptel/zttest.c app called "attest-mod.c". It
> has been modified to report the "delay" in receiving 8,192 bytes
> from the TDM card (instead of reporting a percentage). It works with
> the digium x100p cards as well.
> 
> Drop the attachment in your zaptel directory and compile it with:
>   gcc zttest-mod.c -o zttest-mod.o
> Then run the executable like this:
>   ./zttest-mod.o -v
> and report the results.
> 
> The output should look like:
> 8192 bytes in 1.023843 seconds
> 8192 bytes in 1.023866 seconds
> 8192 bytes in 1.023853 seconds
> 8192 bytes in 1.023876 seconds
> 8192 bytes in 1.023841 secondsr
> --- Results after 5 passes ---
> Best: 1.023876 -- Worst: 1.023841 -- Average: 1.023856
> 
> The design objective of the TDM (and x100p) cards was to transfer
> 8,192 bytes of data from the card in exactly 1.00000 seconds.
> The above sample indicates my system required 1.023856 seconds to
> accomplish this, or 23856 microseconds too late.

Isn't the design objective to read 8000 bytes in one second?  The
reported (roughly) 1.024 second time frame is correct for 8192 bytes.

I get average numbers very close to 1.024 (especially if I take some
rounding error into account).

> Since the data transfer is to late, it implies that one frame of 
> data (or 1,024 bytes) will be dropped every 5.2 seconds on average
> (or, one frame dropped for every 42 received). 
> 
> I'm about 90% sure that's why spandsp does not function correctly
> and probably impacts how well the echo canceller works in some 
> cases as well.
> 
> It would be very interesting to see everyone's results in running
> this, and even more interesting to report the results with the OS
> distro in use, mobo in use (if known), etc. If anyone actually
> get's a result that is very close to 1.000 seconds, I'd really
> like to know more about those systems. (email off list is fine
> if you want.)