DVD-T? Really? What kind of receiver just a usb ATSC tuner etc? Scary to what to think I could do with DVB-S2 and Gnuradio lol Ok great Back to the decoder – ff that fills in some blanks. I put a slicer ahead of the decoder - now I get segv inside the decoder - inside  the general_work method: (running python under gdb...) [New Thread 0x7fffdc1bd700 (LWP 9511)] Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7fffdc9be700 (LWP 9510)] op25_decoder_bf::general_work (this=0x27666b0, nof_output_items=46,nof_input_items=..., input_items=<value optimized out>, output_items=...)     at op25_decoder_bf.cc:92 92            float *out = reinterpret_cast<float*>(output_items[0]); (gdb) bt #0  op25_decoder_bf::general_work (this=0x27666b0, nof_output_items=46,     nof_input_items=..., input_items=<value optimized out>, output_items=...)     at op25_decoder_bf.cc:92 #1  0x00007ffff5f01a3e in gr_block_executor::run_one_iteration() ()    from /usr/local/lib/libgnuradio-core-3.5.3git.so.0.0.0 #2  0x00007ffff5f232cf in gr_tpb_thread_body::gr_tpb_thread_body(boost::shared_ptr<gr_block>, int) () from /usr/local/lib/libgnuradio-core-3.5.3git.so.0.0.0 #3  0x00007ffff5f1c71f in boost::detail::function::void_function_obj_invoker0<gruel::thread_body_wrapp er<tpb_container>, void>::invoke(boost::detail::function::function_buffer&) () from /usr/local/lib/libgnuradio-core-3.5.3git.so.0.0.0 #4  0x00007ffff5c4d015 in boost::detail::thread_data<boost::function0<void> #5  0x00007ffff5193b70 in thread_proxy ()    from /usr/lib/libboost_thread.so.1.40.0 #6  0x00007ffff7bc69ca in start_thread () from /lib/libpthread.so.0 #7  0x00007ffff6aa0cdd in clone () from /lib/libc.so.6 #8  0x0000000000000000 in ?? () (gdb) The code in question looks like: int op25_decoder_bf::general_work(int nof_output_items, gr_vector_int& nof_input_ite ms, gr_vector_const_void_star& input_items, gr_vector_void_star& output_items) { ... float *out = reinterpret_cast<float*>(output_items[0]); I'm not totally familiar with blocks in GNURadio - seems like output_items isn't initialized... Sean From: op25-dev(a)yahoogroups.com [mailto:op25-dev@yahoogroups.com] On Behalf Of Steve Glass Sent: Thursday, March 22, 2012 6:49 PM To: op25-dev(a)yahoogroups.com Subject: Re: [op25-dev] difference between op25.decoder_bf and op25.decoder_ff   Hi, I've just got a funcube myself and just this morning support for it made it into the GNURadio trunk. That should make using them lots easier. I am looking forward to seeing the DVB-T support get done because that will make using SDR much cheaper (23USD delivered!). The question you ask concerns the interface to the decoder... the _ff version has float inputs and outputs and the other takes bytes (actually two-bit symbols) inputs and float outputs. The latter needs a slicer before it but that is conceptually the right thing to do and so the _ff version is deprecated. Hope that helps. Stevie On 23 March 2012 07:48, bdapriv01 &lt;bdapriv01(a)gmail.com&gt; wrote:   Hi Whats the difference between these 2? I'm new to Gnuradio & python to be honest; I'm writing my own ap25 listener for the funcube... So far, I've got my software tuning, FM decoding, and then sending data into the FSK4 decoder; I can see it fine tuning.. but I don't get anything out of the decoder_bf function. Is there any easy way, to debug what its doing?? Digging around in code there doesn't seem to be much debugging. I did create some network sinks, and forward the output of the FM demod to a a scope inside gnuradio companion.. the signal looks like FSK4 with the funky phase changes. Sean