Hello,
on Windows, try "HxD Hex Editor" or "Hexedit" (I use the latter one, but
that doesn't mean it is better, I just came across it first years ago
when I was looking for such a tool). For Linux, use xxd to hexdump a
file, edit it using any text editor, and use xxd -r to convert it back
to binary.
But all of these are dangerous weapons, so use them with a lot of care.
To adjust the RTP headers properly, you need to open the pcap file
first, make yourself familiar with the various fields of the RTP
headers, understand the relationship between them, and also understand
the .pcap format structure. The ability of Wireshark to highlight a
field in the hex dump pane when you click it in the dissection pane
should help you find what to change using the hex editor. But capturing
DTMF generated by a phone and using Wireshark to filter out the
necessary packets may still be a faster way to your goal.
In dtmf_2833_1.pcap, there are 10 packets; in all of them, you have to
change the "sequence number" field to grow monotonously by 1 and start
from a higher value than the last one in the file dtmf_2833_2.pcap; the
"timestamp" value must be the same in all of them (for telephone-event
packets in particular - this is not the case for normal audio or video
codecs), but it has to be higher than the timestamp value in
dtmf_2833_2.pcap.
So rather than editing the pcap file manually, it may be worthier to
write a script that will generate .pcap files as needed for the
particular test scenarios.
P.
Dne 20.05.2022 v 12:20 Vinayak Makwana napsal(a):
Hi
Thanks for your response
My scenario it's as below:
first I am sending DTMF 1 then DTMF 2 and then DTMF 1 again . but 3rd
DTMF 1 is not detected in Freeswitch.
Can you please give me suggestions like how can i change sequence
number or RTP timestamp? and
Can you provide me with a binary editor link from where I can make
changes in the PCAP file?
Regards
Vinayak Makwana
On Wed, May 18, 2022 at 9:22 PM Šindelka Pavel <sinde...@ttc.cz> wrote:
I would assume that the pcap player invoked by SIPp does not
adjust the
RTP sequence numbers and/or RTP timestamps when playing the .pcap
files,
so if the receiving RTP stack checks them, it considers all the
packets
of the second instance to arrive late and ignores them. But it is
weird
if a DTMF received in one call affects its processing in another
call,
is that indeed the case?
If my assumption is correct, you'll have to create a copy of the pcap
file and edit the sequence numbers and/or timestamps using some
editor
of binary files, or capture some real DTMF, or maybe modify the
source
code of the pcap player to take care of this.
Pavel
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