[Discuss-gnuradio] gr-trellis : problem in using viterbi decoder

[Raman O]

Hello ,

     I am using conv encoder and  viterbi decoder in FHSS-BPSK transceiver. Below I have pasted encoder-decoder code which is a part of pure C++ application. Problem is  encoder input and decoder output do not match.
Can anyone point where i am making mistake ?

Thanks in advance
Ram

 int K=100;  
  short inputbits[100]={ ....contains bits....  };
std::vector<short> in_bits;
       
        for (int i = 0; i <K ; i++)  { //  K - no of bits
        in_bits.push_back(inputbits[i]); // input bits
        }
        std::vector<float> constellation; // BPSK mapping
           constellation.push_back(1);
           constellation.push_back(-1);
    
          
         gr_vector_source_s_sptr bit_src = gr_make_vector_source_s(in_bits,false,K );
    
         gr_vector_to_stream_sptr vector2stream= gr_make_vector_to_stream(sizeof(short),K);
    
     // encoder    
           fsm f= fsm("../../../gr-trellis/src/examples/fsm_files/awgn1o2_128.fsm");
           trellis_encoder_ss_sptr encoder = trellis_make_encoder_ss (f, 0);
    
     // modulate
 gr_chunks_to_symbols_sf_sptr mod = gr_make_chunks_to_symbols_sf (constellation, 1);

     // ----------- ideal channel -------------
    
     // decoder
    
     trellis_metric_type_t type= TRELLIS_EUCLIDEAN;
     trellis_metrics_f_sptr metrics = trellis_make_metrics_f (f.O(), 1, constellation, type);
     trellis_viterbi_s_sptr viterbi =trellis_make_viterbi_s ( f,K, 0, -1);
        
     gr_stream_to_vector_sptr stream2vector= gr_make_stream_to_vector(sizeof(short), K);
     d_dst = gr_make_vector_sink_s (K);
             
     connect( bit_src ,   0, vector2stream,   0);
     connect( vector2stream ,   0,mod, 0);
     connect(mod,   0,metrics,   0);
     connect(metrics,   0, viterbi,   0);
     connect( viterbi,   0,stream2vector,   0);
     connect(stream2vector,   0, d_dst, 0);