I am searching for information about ways to automaticly analyze audiofiles for baudrate, modulation frequencies (eg 1200 and 2400 Hz for binary modulation) etc. It's for max 1200 baud, so no HF complications. I am able to load the audio into a bank, so basicly its a simple list of say 16 bit 44.1kHz samples. Any ideas or even sourcecode for spectrum analysis etc?
Need info about modulation analysis
Miscellaneous Forums/General Discussion/Need info about modulation analysis Look up code samples for FFT (Fast Fourier Transforms)
arrgh that's exactly one of those things I never understood :°) I used to read about it when I was trying to become familar with YUF Video encoding. Well seems like I got to try again, thanks.
When searching for "baudrate analysis" google is pointing me mostly to a PCI card named WAVECOM that is used to tap satelite calls of the taliban and what not, costing 7'000 Euros, Pro-version sold only to Government Authorities, allowing to read Inmarsat-C in plaintext and realtime decoded, with a customer reference list containing every secret service in this world.
I think it's time to add this to the code archives then :)
I think it's time to add this to the code archives then :)
I still didn't find anything useful. I mean of course I could read trough tons of stuff and do it "the official way", but I really don't know where to start and how to utilize things like FFT. They are just some abstract theories to me, I don't know how to use them in my code. Maybe I'm dumb yes.
However I have some ideas on how to implement it in a straight forward way. Probably my test wavs are just not good enough for testing.
Basicly it's good that I don't know the modulation details of the test wav, so I cannot cheat. But then again, when I study the evelope, there seem to be multiple frequencies, harmonics, for some reason. Plus the noise since it was recorded with an airband scanner. Well noise isn't such a problem as long as the signal amplitude is high enough.
I had this idea of using various reference baudrate, Bytesize etc. patterns as a mask and if the signal peaks fits the pattern of the mask, it may be watched closer.
Then the detection would create some ascii strings from the bits and try various modes, like 7 bit, 8 bit, 1 stopbit, 2 stopbits etc.
The resulting strings are then compared with a multilingual dictionary and if any existing words are found then it's likely the modulation is decoded.
Maybe I simply need to use an other test wav. Although this one sounds like maybe a 300 Baud signal with 1200 and 2400 modulation, for some reason the two frequencies seem to be overlapping/playing parallely, so I don't know how to read out the bits, even when I see the main frequency of the modulation
Any help is still welcome.
However I have some ideas on how to implement it in a straight forward way. Probably my test wavs are just not good enough for testing.
Basicly it's good that I don't know the modulation details of the test wav, so I cannot cheat. But then again, when I study the evelope, there seem to be multiple frequencies, harmonics, for some reason. Plus the noise since it was recorded with an airband scanner. Well noise isn't such a problem as long as the signal amplitude is high enough.
I had this idea of using various reference baudrate, Bytesize etc. patterns as a mask and if the signal peaks fits the pattern of the mask, it may be watched closer.
Then the detection would create some ascii strings from the bits and try various modes, like 7 bit, 8 bit, 1 stopbit, 2 stopbits etc.
The resulting strings are then compared with a multilingual dictionary and if any existing words are found then it's likely the modulation is decoded.
Maybe I simply need to use an other test wav. Although this one sounds like maybe a 300 Baud signal with 1200 and 2400 modulation, for some reason the two frequencies seem to be overlapping/playing parallely, so I don't know how to read out the bits, even when I see the main frequency of the modulation
Any help is still welcome.