huh ? what kinda DATA stream ???


dunno about Linux , but to do it in MS ...... ( and probably
any other OS )

1. to make that work , you have to know the type of datastream
and then choose appropriate stuff / procedures for that
type of stream.

2. for example ...... to decode the datastream of a trunking
control channel , you need a single level slicer or a
simple schmidt trigger to convert the analog level slicer stream into
a digital level stream. the output is ( often ) plain serial ,
digital, after that. an ordinary " packet " sniffer or serial port
dumper / monitor program could give you the raw data. specific
streams require stream specific programs to decode to useable output.
many programs had " raw " output mode. programs like " pager software
" pager serial streams, trunking software for trunking control
channels, and cellular software for cellular tower data streams.

3. flex / 4 level encoded data streams require a quad level slicer
to separate the digital data streams properly. then you need an
appropriate program with " raw " output ( many of them have it )
for that stream..... like in decoding " flex " paging systems.
raw dumps of 4 level slicers would likely only produce
confusing ( to humans ) meaningless looking output.

4. if your signal is a digital " codec " wireless mike , for example ,
then you must use a schmidt trigger or single level slicer into
an external compatible " codec " chip intermediate translator
device to properly decode the datastream. optionally you can
, if you know how, use the MS selection of audio codecs contained
within every current MS OS and choose one of them to decode the stream
and output it through your sound card. a " raw " output of this type
stream is of NO human value , except for design and testing purposes.
there are many more types and variations of digital data stream
handling. you must know the type of stream and develop a strategy to
manage THAT particular type of digital demodulation. your program /
hardware selection " must " address the specific type of stream you
anticipate encountering.

many people utilize an " intermediate " decoding device to accomplish
digital signal decoding. apco 25 digital , for example , has NO MS OS
specific codec . it takes a specialized apco 25 decoding chip to
deliver the digital voice codec from a apco 25 encoded signal. people
might buy a used 1st gen apco 25 HT on ebay and then feed the output
from a single level slicer into the decoder chip portion of the HT to
obtain a voice output from the disc signal output. this has been used
successfully , all the way back into the early cellular telephone days
when old brick phones were used simply for their decoder chips to
feed the output from a scanner into . a study of those old cellular
digital decoding processes are a good resource for this type of
endeavor.



it's WAY more complicated than most people expect.



k............





On 26 Aug 2005 10:51:00 -0700, wrote:

Hi All!
can anybody post a small example in c/c++ for linux which would print
raw data stream from discriminator?

thanks.