readdata.m

ITU-T G.723.1 Speech Coder: Matlab implementation This package implements the speech coder and de

function QC = ReadData (FNameI, FNameErr)
% Read data for the G.723.1 decoder
% Input data is either from a bitstream file or a Matlab file.
% For the case of a bitstream file, an optional frame error
% file can be specified (contains an error flag for each frame)

% $Id: ReadData.m 1.4 2004/08/06 G.723.1-v2r1a $

% Read data for either a bitstream file or a Matlab file
QC = ReadInputFile (FNameI);

% Declare errors as set by the frame error file
if (~ isempty (FNameErr))
  QC = ReadErrFile (FNameErr, QC);
end

% Check for "forbidden codes"
if (isfield (QC, 'FType'))
  NFrame = length (QC);
  for (i = 1:NFrame)
    if (CheckQCErr (QC(i)))
      QC(i) = NullStruct (QC(i));
      QC(i).FType = 4;
    end
  end
end

return

% ----------
function [VC, BitStream] = ReadInputFile (FName)

% Open the file for a peek at the first 6 characters
fid = fopen (FName, 'r');
if (fid == -1)
  error ('G7231Decoder: Cannot open input file');
end
id = char (fread (fid, 6, 'uchar')');
fclose (fid);

BitStream = (~ strcmp (id, 'MATLAB'));

% Read the file
if (BitStream)
  VC = ReadG7231Stream (FName);
else
  load (FName, '-mat');    % Loads VC
  fprintf ('G723.1 data file: %s\n', FullName (FName));
end

return
% ----------
function QC = ReadErrFile (FName, QC)
% Read the frame error file; set the frame type in QC
% for error frames

NFrame = length (QC);

fid = fopen (FName, 'r', 'l');        % Little-endian
if (fid == -1)
  error ('G7231Decoder: Cannot open input frame error file');
end
FErr = (fread (fid, Inf, 'uint16') ~= 0);
fclose (fid);

fprintf ('G.723.1 Frame error file: %s\n', FullName (FName));

if (length (FErr) ~= NFrame)
  error ('G7231Decoder: Invalid frame error file length');
end
  
% Set FType for marked frames from the frame error file
for (i = 1:NFrame)
  if (FErr(i) ~= 0)
    QC(i) = NullStruct (QC(i));
    QC(i).FType = 4;
  end
end

return

% ----------
function Err = CheckQCErr (QC)
% Check whether the data has "forbidden" values
% - The last 4 pitch lag values are forbidden
% - The pitch coefficient values must be in bounds

ACBLCMax = 123;     % PMax = ACBLCMax + 18
ACBLCThr = 40;      % LThr = ACBLCThr + 18, threshold for 85 codebook (MP only)
GModV = {[1 24 2048]; [1 24]};
Nb = [85; 170];

Err = 0;
if (QC.FType == 0 | QC.FType == 1)
  Err = (QC.ACBLC(1) > ACBLCMax | QC.ACBLC(3) > ACBLCMax);
  CBookI(1:4) = 2;
  if (QC.FType == 0)
    if (QC.ACBLC(1) < ACBLCThr)
      CBookI(1:2) = 1;
    end
    if (QC.ACBLC(3) < ACBLCThr)
      CBookI(3:4) = 1;
    end
  end
  for (i = 1:4)
    [gC, ACBbC] = ExtractVals (QC.CGC(i), GModV{CBookI(i)});
    if (ACBbC >= Nb)
      Err = 1;
    end
  end
end

return

% ----------
function SN = NullStruct (S)
% Create a structure element with null fields with the
% same fields as an input structure

St = S(1);            % Sample element from the stucture
FN = fieldnames (St);
% St(2).(FN{1}) = [];            % Only for Matlab 6.5 and later
eval (['St(2).' FN{1} ' = [];']); % Create a null element
SN = St(2);

return