Luki wrote:
That file is very screwed up. Every 5ms the sine wave hiccups. Thus,
instead of a mellow single note, it blows raspberries at you. The reason
for this is left as an exercise for the reader.
It's like: it should be obvious to the casual observer that... :).
But seriously, the wave does look chopped off every 5 ms but for some
reason the third tone is almost OK (after a ~40 ms). The rest is
garbage.
I took a tcpdump and had a look in wireshark and noticed something
strange. Normal alaw (voice) traffic uses around 80kbps and I see the
same number of packets in either direction (172 bytes every 20ms).
However, when I execute TxFax I see two g711 alaw packets going out for
every one coming back, so my outbound throughput is around 160kbps now.
The second packet's payload looks similar to the first, almost like a
duplicate.
Does spandsp/openpbx do some kind of 'payload redundancy' (i.e. transmit
each RTP packet twice?) and if so can this be disabled? I wonder if our
Cisco gateway is confused about the 2 alaw RTP packets arriving within
5ms of each other?
Here is a cut and paste of the tcpdump output I see during TxFax sending
out fax tones:
18:29:01.940036 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:29:01.940120 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:01.953296 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:01.960347 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:29:01.960434 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:01.969289 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:01.980498 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:29:01.980583 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:01.989295 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:02.000955 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:29:02.001046 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:29:02.009297 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
... whilst here is normal Voice traffic from OPBX using alaw:
18:28:51.510384 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:28:51.519825 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:28:51.530379 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:28:51.539978 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:28:51.550378 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:28:51.560278 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:28:51.570375 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
18:28:51.580610 IP gateway.sipprov.com.38134 > opbx.mydomain.com.38748:
UDP, length 172
18:28:51.590372 IP opbx.mydomain.com.38748 > gateway.sipprov.com.38134:
UDP, length 172
Any advice would be greatly appreciated.
Cheers,
Ray
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