I was getting segmentation faults whenever starting to decode a P25 signal. (A stack trace is at the bottom of my message.) After a bit of investigating, I found that the value of the OldL variable in software_imbe_decoder was getting used before it was initialized. Adding OldL = 0 to the constructor got rid of the segfaults, but I don't understand the code well enough to know whether it's the correct fix. Regards, Clayton ---------- [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Core was generated by `python ./top_block.py'. Program terminated with signal 11, Segmentation fault. #0 0x00007f6e2bcb15a3 in software_imbe_decoder::decode_spectral_amplitudes (this=0x39fa940, Start3=<optimized out>, Start8=<optimized out>) at software_imbe_decoder.cc:1006 1006 for(ell = OldL + 1; ell <= L + 1; ell++) { log2Mu[ell][ Old] = log2Mu[OldL][ Old]; } (gdb) i stack #0 0x00007f6e2bcb15a3 in software_imbe_decoder::decode_spectral_amplitudes (this=0x39fa940, Start3=<optimized out>, Start8=<optimized out>) at software_imbe_decoder.cc:1006 #1 0x00007f6e2bcb305d in software_imbe_decoder::decode_audio (this=0x39fa940, A=<optimized out>) at software_imbe_decoder.cc:913 #2 0x00007f6e2bcb3747 in software_imbe_decoder::decode (this=0x39fa940, cw=...) at software_imbe_decoder.cc:810 #3 0x00007f6e2bc9ea7b in voice_data_unit::do_decode_audio (this=<optimized out>, frame_body=..., imbe=...) at voice_data_unit.cc:50 #4 0x00007f6e2bc98b01 in abstract_data_unit::decode_audio (this=0x7f6dc8000e10, imbe=...) at abstract_data_unit.cc:61 #5 0x00007f6e2bc9ec0a in voice_du_handler::handle (this=0x39fdee0, du=...) at voice_du_handler.cc:45 #6 0x00007f6e2bcad4f8 in op25_decoder_bf::receive_symbol (this=0x39fa4f0, d=2 '\002') at op25_decoder_bf.cc:214 #7 0x00007f6e2bcad980 in op25_decoder_bf::general_work (this=0x39fa4f0, nof_output_items=16, nof_input_items=..., input_items=..., output_items=...) at op25_decoder_bf.cc:86 #8 0x00007f6e31d09ae3 in gr_block_executor::run_one_iteration() () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #9 0x00007f6e31d28d5d in gr_tpb_thread_body::gr_tpb_thread_body(boost::shared_ptr<gr_block>, int) () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #10 0x00007f6e31d23996 in boost::detail::function::void_function_obj_invoker0<gruel::thread_body_wrapper<tpb_container>, void>::invoke(boost::detail::function::function_buffer&) () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #11 0x00007f6e31548a9e in boost::detail::thread_data<boost::function0<void> >::run() () from /usr/local/lib/libgruel-3.6.1git.so.0.0.0 #12 0x00007f6e30eebce9 in thread_proxy () from /usr/lib/libboost_thread.so.1.46.1 #13 0x00007f6e340e2e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #14 0x00007f6e32ed44bd in clone () from /lib/x86_64-linux-gnu/libc.so.6 #15 0x0000000000000000 in ?? ()