Re: file-transfer-over-soundcard

[Brian Inglis <Brian dot Inglis at SystematicSw dot ab dot ca>]

Spet <spora <at> email.it> writes:
> -------- Original Message --------
> > On May 21, 2015, at 1:03 AM, Spet <spora <at> email.it> wrote:
> >>
> >> When i execute from dos console:
> >
> > Why arenât you using Cygwin Terminal instead?
> This is my first time.
> However I have to use it in windows console.
> >
> > The Cygwin Terminal has a huge number of features missing from the
Windows console, some of which allow it
> to work better with Cygwin programs.  (UTF-8 support, for example.)
> >
> > Meanwhile, the DOS console offers zero advantage over the Cygwin
Terminal when it comes to running Cygwin executables.
> Ok
> >
> >> ./generate.exe -b 25 -r 48000 -o out.data /etc/fstab

> > Anyway, it works here.  I get a 25 MiB sound output file for a 531 byte
/etc/fstab.
> Now here, I understood better how it works.
> >
> >> generate.exe -b 25 -r 48000 -o "k:\TEMP\a.txt" c:\cygwin\etc\fstab
> >
> > Are you sure you built it with the Cygwin C compiler, and not something
else, like the MinGW or Visual Studio
> compilers?  Thatâs the only explanation I can think of for why the POSIX
path (/etc/fstab) would fail,
> but a DOS path would succeed.
> I've only done "makefile" in terminal.
> >
> > I have to ask: Why do you even want this software?
> Just a curiosity to transmit files via audio and compile a C source 
> Linux in Windows.
> 
> Finally, the compilation work.  The sound file is recorded and the audio 
> capture works.
> But the transmission of the file fails because I get a bit sequence 
> completely different from the original.
> 
> Ty :)

The original article
https://github.com/vlofgren/file-transfer-over-soundcard author tried to
reinvent the wheel - badly! 
He tried to build a bit to audio converter - a modem in software, softmodem
aka soundmodem, which does in software what a modem does in hardware,
ignoring almost a century of development since the news wires started using
teleprinters. 
His hardware interface was a microphone taped to headphones rather than a
simple cable connection - no wonder he had noise problems limiting him to 25
bps, the same rate achieved by IBM with cards in 1942 - see
https://en.wikipedia.org/wiki/Modem#History - when lines used one wire, and
switching was relays, electro-mechanical, or plugboards. 

Look instead for something reasonable - search for softmodem or soundmodem
e.g. http://www.araneus.fi/audsl which gets 9.6kB/s duplex over kms of wire
pair. You can also find code to do regular V.92bis dialup modem emulation. 
Regular soundcards should be capable of 4x dialup bandwidth, allowing up to
72kB/s. 
-- 
Take care. Thanks, Brian Inglis