Hello,
For V.21 speeds, spandsp works fine. I wrote a couple of Asterisk bindings for spandsp modems, to do 50baud 5bit tty, 300baud Bell, 1200/75 V.23 Minitel/BTX. That was no issue at all. I should have these lines open to CNET, if someone wants to try.
Christoph
Am 29. Februar 2024 03:19:55 GMT-07:00 schrieb Mychaela Falconia falcon@freecalypso.org:
Hi Sarah,
there's no really good option for this right now (especially at higher speeds), but supersat wrote this yate module to run an old "Winmodem" driver binary (sl-modem) from a PBX. [...] https://github.com/Shadytel/shadysoftmodem
I looked at the source tree at that link, and - please correct me if I got it wrong - it seems to me that it uses some binary-only *.o code pieces, i.e., blobs. If this solution is indeed blobware, then it is very UNattractive...
However, prior to your reply, Christoph Lauter pointed me to spandsp - seeing that name in Chris' response jogged my memory, I now recall someone else (perhaps it was you?) mentioning spandsp to me earlier, in some OsmoDevCall or RetroNetCall chat.
I cloned spandsp from github and started looking at it. At first glance the code looks very complete, and appears to have all of the pieces I am looking for. However, the giant red flag I see there is almost complete absence of documentation. Sure, there are some sprinkled doxygen comments, but no REAL documentation. I wonder if perhaps Steve U (the author of spandsp) follows a business model where the code is released under GPL, but instead of proper documentation that would allow anyone to self-support, he offers paid support to those who need it badly enough...
When I have more time (always the big uncertainty), I will try digging through that spandsp code a bit harder, with a goal of figuring out how to exercise V.21 modem functions for a start, and try building a SIP+RTP 300 baud modem on top of the lib - and I may also try emailing Steve U and asking him about his support offerings...
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