On 09.02.2012 17:11, Patrick Boettcher wrote:
On Thursday 09 February 2012 16:01:12 Antti Palosaari wrote:
I have taken radio sniffs from FM capable Realtek DVB-T device. Looks
like demodulator ADC samples IF frequency and pass all the sampled
data to the application. Application is then responsible for
decoding that. Device supports DVB-T, FM and DAB. I can guess both
FM and DAB are demodulated by software.
Here is 17 second, 83 MB, FM radio sniff:
http://palosaari.fi/linux/v4l-dvb/rtl2832u_fm/
Decode it and listen some Finnish speak ;)
Could someone help to decode it? I tried GNU Radio, but I failed
likely because I didn't have enough knowledge... GNU Radio and
Octave or Matlab are way to go.
For someone to decode it, you would need to give more information about
the format of the stream. Like the sampling frequency, the sample-format
and then the IF-frequency.
You can see sampling format easily looking hexdump or open file in
Audacity. It is 8bit unsigned samples, 2 channels (I & Q).
No knowledge about IF... For good guess is to try some general used IFs.
Sampling freq can be calculated using sample info and the fact it is
about 17 sec. sample size = 86919168 Bytes, time 17 sec. 2 channels, 1
byte sample => 2556446,11765 sample/sec (~2.5 MHz!)
I never did something like myself, but from what I saw in gnuradio there
should be everything to make a FM-demod based on the data.
Yes there was a lot of block and those were rather easy to connect using
graphical interface (gnuradio-companion). But I don't know exactly what
block are needed and what are parameters. I used file-sink =>
fm-modulator => audio-sink. Likely not enough :i
Without any earlier experience it is rather challenging. But if there is
someone who have done that earlier using USRP SDR he could likely do it
easier :)
regards
Antti
--
http://palosaari.fi/
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
