readg7231stream.m

来自「ITU-T G.723.1 Speech Coder: Matlab imple」· M 代码 · 共 63 行

function QC = ReadG7231Stream (FName, Frames)
% Read a byte stream file generated by a ITU-T G.7231 coder,
% returning the code values for selected frames.

% $Id: ReadG7231Stream.m 1.4 2004/08/07 G.723.1-v2r1a $

if (nargin < 2)
  Frames = [1, Inf];
end

FID = fopen (FName);
if (FID == -1)
  ErrMsg = sprintf ('Cannot open bitstream file: %s', FullName (FName));
  error (ErrMsg);
end
fprintf ('G.723.1 Bitstream file: %s\n', FullName (FName));

IFr = 1;
k = 1;
while (IFr <= Frames(2))

  v = fread (FID, 1, 'uchar');
  if (isempty (v))
    break;
  end
  BT(1) = v;

  % Check the bit rate bits to determine the frame size (bytes)
  v = bitand (BT(1), 3);
  switch (v)
    case 0    % High rate
      N = 24;
    case 1    % Low rate
      N = 20;
    case 2    % SID frame
      N = 4;
    otherwise % Untransmitted frame
      N = 1;
  end

  if (N > 1)
    Data = fread (FID, N - 1, 'uchar');
    if (length (Data) ~= N - 1)
      error ('Invalid bitstream file');
    end
    BT(2:N) = Data;
  end

  if (IFr >= Frames(1))
    ByteStream{k} = BT;
    k = k + 1;
  end
  
  IFr = IFr + 1;
end

fclose (FID);

% Convert to codes
QC = GetQCodes (ByteStream);

return