videoreader_load.m

Video IO toolbox for matlab. 用directshow做的

function [out,out2] = videoReader_load(cmd, handle, varargin)
%[...] = videoReader_load(cmd, handle, varargin)
%  videoReader plugin for reading videos stored as individual images in
%  MAT files (one image per MAT file).  This plugin uses Matlab's LOAD 
%  function to read the frames and is implemented as M-code instead of 
%  as a MEX function.  Users should not call this function directly.  
%  Instead they should use the videoReader constructor and specify the 
%  'load' plugin.  
%
%  Type 'help videoReader' for usage documentation.
%
%Example:
%  % make a few video frames -- a rotating gradient
%  for i=1:10
%    frame = repmat(mod([0:99]/99 + (i-1)/10, 1), [75,1]);
%    save(sprintf('%04d.mat', i), 'frame');
%  end
%  % read in the video and show it as a movie
%  vr = videoReader('%04d.mat', 'plugin','load', 'varname','frame');
%  for i=1:10
%    seek(vr,i);
%    imshow(getframe(vr));
%    title(sprintf('frame %d', i));
%    pause(1);
%  end
%  vr = close(vr);
%
%Copyright (c) 2008 Gerald Dalley
%See "MIT.txt" in the installation directory for licensing details (especially
%when using this library on GNU/Linux). 

persistent nextHandle handles varnames dirnames filenames currFrames infos;
if isempty(nextHandle)
  nextHandle = int32(now);
  handles    = int32(zeros(0,0));
  varnames   = {};
  dirnames   = {};
  filenames  = {};
  currFrames = [];
  infos      = {};
end

i = validateHandle(cmd,handle,handles);

if strcmp(cmd, 'close'),
  %........................................................................
  % CLOSE COMMAND
  if ~isempty(varargin)
    error('The "close" command does not take any optional arguments');
  end
  handles    = handles([1:i-1, i+1:end]);
  dirnames   = {dirnames{[1:i-1, i+1:end]}};
  filenames  = {filenames{[1:i-1, i+1:end]}};
  currFrames = currFrames([1:i-1, i+1:end]);
  infos      = {infos{[1:i-1, i+1:end]}};
  
elseif strcmp(cmd, 'getframe')
  %........................................................................
  % GETFRAME COMMAND
  if ~isempty(varargin)
    error('The "getframe" command does not take any optional arguments');
  end
  dirname = dirnames{i};
  fname   = filenames{i}{currFrames(i)+1};
  out     = loadFrame(varnames{i}, dirname, fname);
  
elseif strcmp(cmd, 'getinfo')
  %........................................................................
  % GETINFO COMMAND
  if ~isempty(varargin)
    error('The "getinfo" command does not take any optional arguments');
  end
  out  = fieldnames(infos{i});
  out2 = struct2cell(infos{i});
  
elseif strcmp(cmd, 'next')
  %........................................................................
  % NEXT COMMAND
  if ~isempty(varargin)
    error('The "next" command does not take any optional arguments');
  end
  currFrames(i) = currFrames(i) + 1;
  if currFrames(i) < infos{i}.numFrames
    out = int32(1);
  else
    out = int32(0);
  end
  
elseif strcmp(cmd, 'open')
  %........................................................................
  % OPEN COMMAND
  i = length(handles)+1;
  handles(i) = nextHandle;
  out        = nextHandle;
  nextHandle = int32(double(nextHandle)+1);
  
  if (mod(length(varargin)-1,2) ~= 0)
    error('Optional arguments must come in name-value pairs');
  end
  varnames{i} = '';
  for j=2:2:length(varargin)
    if (strcmp(varargin{j}, 'varname'))
      varnames{i} = varargin{j+1};
    else
      error(['Unrecognized optional argument name: ', varargin{j}]);
    end
  end
  
  filepattern = varargin{1};
  [dirnames{i}, filenames{i}] = getFileList(filepattern);
  
  img = loadFrame(varnames{i}, dirnames{i}, filenames{i}{end});
  currFrames(i) = -1;
  infos{i}      = struct(...
    'url',                varargin{1}, ...
    'fps',               -1, ...
    'height',             size(img,1), ...
    'width',              size(img,2), ...
    'numFrames',          length(filenames{i}), ...
    'fourcc',             '',...
    'nHiddenFinalFrames', 0,...
    'varname',            varnames{i});
  
elseif strcmp(cmd, 'seek')
  %........................................................................
  % SEEK COMMAND
  if length(varargin) ~= 1
    error('The "seek" command takes exactly one argument');
  end
  currFrames(i) = varargin{1};
  if currFrames(i) < infos{i}.numFrames && currFrames(i) >= 0
    out = int32(1);
  else
    out = int32(0);
  end
  
elseif strcmp(cmd, 'step')
  %........................................................................
  % STEP COMMAND
  if length(varargin) ~= 1
    error('The "step" command takes exactly one argument');
  end
  currFrames(i) = currFrames(i) + varargin{1};
  if currFrames(i) < infos{i}.numFrames && currFrames(i) >= 0
    out = int32(1);
  else
    out = int32(0);
  end
  
else
  error(['Unrecognized command: "' cmd '"']);
end

%--------------------------------------------
function i = validateHandle(cmd,handle,handles)
if strcmp(cmd, 'open')
  if (handle ~= int32(-1))
    % This is a slightly pedantic check to detect if someone has been
    % messing with the constructor or is trying to call us directly.
    error('Unexpected handle for the "open" command');
  end
  i = int32(-1);
else
  [tst,i] = ismember(handle,handles);
  if ~tst
    error('Invalid load plugin handle');
  end
end

%--------------------------------------------
function out = loadFrame(varname, dirname, fname)
if isempty(varname)
  tmp = load(fullfile(dirname, fname));
  % choose the biggest 2D or 3D matrix
  fnames = fieldnames(tmp);
  scores = zeros(numel(fnames),1);
  vals = struct2cell(tmp);
  for j=1:length(scores)
    scores(j) = getVariableScore(vals{j});
  end
  [dummy,fieldIdx] = max(scores);
  out = getfield(tmp, fnames{fieldIdx}); %#ok<GFLD> -- better backward compatibility
else
  out = getfield(load(fullfile(dirname, fname), varname), ...
    varname); %#ok<GFLD> -- better backward compatibility
end

%--------------------------------------------
function score = getVariableScore(x)
%score = getVariableScore(x)
%  Assigns a heuristic score to the variable x.  Variables that look
%  like images (are 2D or 3D numeric matrices) receive very high
%  scores.  Bigger variables get higher scores that smaller ones.  All
%  variables receive a non-zero score.

% soft-decision bias (makes desired features soft constraints)
soft = 1e-10; 

sz = size(x);
if length(sz) < 2
  nPix = numel(x);
else
  nPix = sz(1)*sz(2);
end

score = ...
  ((((ndims(x)==3)+soft) * ((size(x,3)==3)+soft)) +... % rgb or
  ((ndims(x)==2)+soft)) * ...                         %  grayscale
  (nPix+soft) * ...                                    % and big
  (isnumeric(x)+soft);                                 % and numeric