Initial commitHEADmaster

* codec2 cut-down version 1.2.0
* Remove codebook and generation of sources
* remove c2dec c2enc binaries
* prepare for emscripten

1 files changed, 144 insertions, 0 deletions

diff --git a/octave/ofdm_ldpc_tx.m b/octave/ofdm_ldpc_tx.m
new file mode 100644
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+++ b/octave/ofdm_ldpc_tx.m
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+% ofdm_ldpc_tx.m
+% David Rowe April 2017
+%
+% File based ofdm tx with LDPC encoding and interleaver.  Generates a
+% file of ofdm samples, including optional channel simulation.
+
+#{ 
+  1. 10 seconds, AWGN channel at SNR3k=3dB
+
+    octave:4> ofdm_ldpc_tx("test_700d.raw", "700D", 10, 3)
+
+  2. 10 seconds, multipath poor channel at SNR=6dB
+
+    octave:5> ofdm_ldpc_tx("test_700d.raw", "700D", 10, 6, "mpp")
+    
+  3. Data mode example, three bursts of one packet each, SNR=100dB:
+  
+    octave:6> ofdm_ldpc_tx("test_datac0.raw","datac0",1,100,"awgn","bursts",3)
+    
+  4. Data mode example, three bursts of one packet each, SNR=100dB, with CRC
+     to enable demodulation by freedv_data_raw_rx:
+  
+    octave:6> ofdm_ldpc_tx("test_datac0.raw","datac0",1,100,"awgn","bursts",3, "crc")
+    
+#}
+
+function ofdm_ldpc_tx(filename, mode="700D", N, SNR3kdB=100, channel='awgn', varargin)
+  ofdm_lib;
+  ldpc;
+  gp_interleaver;
+  channel_lib;
+  pkg load signal;
+  randn('seed',1);
+  more off;
+
+  tx_clip_en = 0; freq_offset_Hz = 0.0; burst_mode = 0; Nbursts = 1;
+  crc_mode = 0;
+  i = 1;
+  while i<=length(varargin)
+    if strcmp(varargin{i},"txclip") 
+      tx_clip_en = 1;
+    elseif strcmp(varargin{i},"bursts") 
+      burst_mode = 1;
+      Nbursts = varargin{i+1}; i++;
+    elseif strcmp(varargin{i},"crc") 
+      crc_mode = 1;
+     else
+      printf("\nERROR unknown argument: %s\n", varargin{i});
+      return;
+    end
+    i++;      
+  end
+ 
+  % init modem
+
+  config = ofdm_init_mode(mode);
+  states = ofdm_init(config);
+  print_config(states);
+  ofdm_load_const;
+
+  if burst_mode
+    % burst mode: treat N as Npackets
+    Npackets = N; 
+  else
+    % streaming mode: treat N as Nseconds
+    Npackets = round(N/states.Tpacket);
+  end
+
+  % some constants used for assembling modem frames
+  [code_param Nbitspercodecframe Ncodecframespermodemframe] = codec_to_frame_packing(states, mode);
+
+  % OK generate a modem frame using random payload bits
+
+  if strcmp(mode, "2020")
+    payload_bits = round(ofdm_rand(Ncodecframespermodemframe*Nbitspercodecframe)/32767);
+  else
+    payload_bits = round(ofdm_rand(code_param.data_bits_per_frame)/32767);
+    if crc_mode
+      unpacked_crc16 = crc16_unpacked(payload_bits(1:end-16));
+      payload_bits(end-15:end) = unpacked_crc16;
+    end
+  end
+  [packet_bits bits_per_packet] = fec_encode(states, code_param, mode, payload_bits);
+
+  % modulate to create symbols and interleave
+  tx_symbols = [];
+  for b=1:bps:bits_per_packet
+    if bps == 2 tx_symbols = [tx_symbols qpsk_mod(packet_bits(b:b+bps-1))]; end
+    if bps == 4 tx_symbols = [tx_symbols qam16_mod(states.qam16, packet_bits(b:b+bps-1))]; end
+  end
+  assert(gp_deinterleave(gp_interleave(tx_symbols)) == tx_symbols);
+  tx_symbols = gp_interleave(tx_symbols);
+
+  % generate txt (non FEC protected) symbols
+  txt_bits = zeros(1,Ntxtbits);
+  txt_symbols = [];
+  for b=1:bps:length(txt_bits)
+    if bps == 2 txt_symbols = [txt_symbols qpsk_mod(txt_bits(b:b+bps-1))]; end
+    if bps == 4 txt_symbols = [txt_symbols qam16_mod(states.qam16,txt_bits(b:b+bps-1))]; end
+  end
+
+  % assemble interleaved modem packet that include UW and txt symbols
+  modem_packet = assemble_modem_packet_symbols(states, tx_symbols, txt_symbols);
+
+  % sanity check
+  [rx_uw rx_codeword_syms payload_amps txt_bits] = disassemble_modem_packet(states, modem_packet, ones(1,length(modem_packet)));
+  assert(rx_uw == states.tx_uw);
+
+  % create a burst of concatenated packets
+  atx = ofdm_txframe(states, modem_packet); tx = [];
+  for f=1:Npackets
+    tx = [tx atx];
+  end
+  if length(states.data_mode)
+    % note for burst mode postamble provides a "column" of pilots at the end of the burst
+    tx = [states.tx_preamble tx states.tx_postamble];
+  end
+  
+  % if burst mode concatenate multiple bursts with spaces
+  if burst_mode
+    atx = tx; tx = zeros(1,states.Fs); on_time = 0; off_time = states.Fs;
+    for b=1:Nbursts
+      tx = [tx atx zeros(1,states.Fs)];
+      on_time += length(atx);
+      off_time += states.Fs;
+    end
+    % adjust channel simulator SNR setpoint given (burst on length)/(total length including silence) ratio
+    mark_space_SNR_offset = 10*log10(on_time/(on_time+off_time));
+    SNRdB_setpoint = SNR3kdB + mark_space_SNR_offset;
+    printf("SNR3kdB: %4.2f Burst offset: %4.2f SNRdB_setpoint: %4.2f\n", SNR3kdB, mark_space_SNR_offset, SNRdB_setpoint)
+  else
+    SNRdB_setpoint = SNR3kdB; % no adjustment to SNR in streaming mode
+  end
+
+  printf("Npackets: %d  Nbursts: %d  ", Npackets, Nbursts);
+  states.verbose=1;
+  tx = ofdm_hilbert_clipper(states, tx, tx_clip_en);
+  [rx_real rx] = ofdm_channel(states, tx, SNRdB_setpoint, channel, freq_offset_Hz);
+  frx = fopen(filename,"wb"); fwrite(frx, rx_real, "short"); fclose(frx);
+  if length(rx) >= states.Fs
+    figure(1); clf; plot(20*log10(abs(fft(rx(1:states.Fs)/16384))));
+    axis([1 states.Fs -20 60])
+  end
+endfunction