added a script that reads a signal stored using the ibyte format, quantizes the signal using the specified number of bits, and writes the signal to an output file.

src/utils/matlab/libs/quantize_signal.m

@@ -0,0 +1,84 @@
+%
+% \file quantize_signal.m
+% \brief This file opens a binary file using the ibyte format, reads and 
+% quantizes the signal using the most significant nbits, and stores the 
+% quantized signal into an output file. The output file also uses the 
+% ibyte format.
+% \author Marc Majoral, 2020. mmajoral(at)cttc.es
+%
+% Usage: quantize_signal (infile, outfile, nbits)
+%
+%   Inputs:
+%       infile          - Input file name
+%       outfile         - Output file name
+%       nbits           - number of quantization bits
+%
+% -------------------------------------------------------------------------
+%
+% Copyright (C) 2010-2020  (see AUTHORS file for a list of contributors)
+%
+% GNSS-SDR is a software defined Global Navigation
+%           Satellite Systems receiver
+%
+% This file is part of GNSS-SDR.
+%
+% SPDX-License-Identifier: GPL-3.0-or-later
+%
+% -------------------------------------------------------------------------
+%
+function quantize_signal (infile, outfile, nbits)
+
+%% usage: quantize_signal (infile, outfile, nbits)
+%%
+%% open input signal file infile, quantize the signal using the most
+%% significant nbits and write the quantized signal to outfile
+%%
+
+fileID = fopen(infile, 'rb');
+fileID2 = fopen(outfile, 'wb');
+
+% initialize loop
+BlockSize = 20000000;   % processing block size
+NumBitsPerSample = 8;   % num. bits per sample ibyte format.
+NumBitsSHift = NumBitsPerSample - nbits;
+DivVal = 2^NumBitsSHift;
+Lim2sCompl = 2^(NumBitsPerSample - 1) - 1;
+Base2sCompl = 2^NumBitsPerSample;
+do = true;
+data_bytes = fread(fileID, BlockSize);
+
+while do
+    
+    % 2's complement 
+    for k=1:length(data_bytes)
+        if (data_bytes(k) > Lim2sCompl)
+            data_bytes(k) = -Base2sCompl + data_bytes(k);
+        end
+    end         
+    
+    % take the nbits most significant bits
+    data_bytes = floor(data_bytes/DivVal);
+    
+    % quantization correction
+    data_bytes = data_bytes*2 + 1;
+
+    % 2's complement
+    for k=1:length(data_bytes)
+        if (data_bytes(k) < 0)
+            data_bytes(k) = Base2sCompl + data_bytes(k);
+        end
+    end     
+    
+    % write result
+    fwrite(fileID2, data_bytes);
+    
+    if (size(data_bytes) < BlockSize)
+        do = false;
+    else
+        data_bytes = fread(fileID,BlockSize);
+    end
+end
+
+% close files
+fclose(fileID);
+fclose(fileID2);