gusucode.com > audiovideo工具箱matlab源码程序 > audiovideo/@VideoReader/read.m
function varargout = read(obj, index, outputformat)
%READ Read a video file.
% READ will be removed in a future release. Use READFRAME instead.
%
% VIDEO = READ(OBJ) reads in all video frames from the file associated
% with OBJ. VIDEO is an H x W x B x F matrix where:
% H is the image frame height
% W is the image frame width
% B is the number of bands in the image (e.g. 3 for RGB),
% F is the number of frames read
% The class of VIDEO depends on the data in the file.
% For example, given a file that contains 8-bit unsigned values
% corresponding to three color bands (RGB24), video is an array of
% uint8 values.
%
% VIDEO = READ(OBJ,INDEX) reads only the specified frames. INDEX can be
% a single number or a two-element array representing an INDEX range
% of the video stream. Use Inf to represent the last frame of the file.
%
% For example:
%
% VIDEO = READ(OBJ, 1); % first frame only
% VIDEO = READ(OBJ, [1 10]); % first 10 frames
% VIDEO = READ(OBJ, Inf); % last frame only
% VIDEO = READ(OBJ, [50 Inf]); % frame 50 thru end
%
% If an invalid INDEX is specified, MATLAB throws an error.
%
% VIDEO = READ(___,'native') always returns data in the format specified
% by the VideoFormat property, and can include any of the input arguments
% in previous syntaxes. See 'Output Formats' section below.
%
% Output Formats
% VIDEO is returned in different formats depending upon the usage of the
% 'native' parameter, and the value of the obj.VideoFormat property:
%
% VIDEO Output Formats (default behavior):
%
% obj.VideoFormat Data Type VIDEO Dimensions Description
% --------------- --------- ---------------- ------------------
% 'RGB24' uint8 MxNx3xF RGB24 image
% 'Grayscale' uint8 MxNx1xF Grayscale image
% 'Indexed' uint8 MxNx3xF RGB24 image
%
% VIDEO Output Formats (using 'native'):
%
% obj.VideoFormat Data Type VIDEO Dimensions Description
% --------------- --------- ---------------- ------------------
% 'RGB24' uint8 MxNx3xF RGB24 image
% 'Grayscale' struct 1xF MATLAB movie*
% 'Indexed' struct 1xF MATLAB movie*
%
% Motion JPEG 2000 VIDEO Output Formats (using default or 'native'):
%
% obj.VideoFormat Data Type VIDEO Dimensions Description
% --------------- --------- ---------------- ------------------
% 'Mono8' uint8 MxNx1xF Mono image
% 'Mono8 Signed' int8 MxNx1xF Mono signed image
% 'Mono16' uint16 MxNx1xF Mono image
% 'Mono16 Signed' int16 MxNx1xF Mono signed image
% 'RGB24' uint8 MxNx3xF RGB24 image
% 'RGB24 Signed' int8 MxNx3xF RGB24 signed image
% 'RGB48' uint16 MxNx3xF RGB48 image
% 'RGB48 Signed' int16 MxNx3xF RGB48 signed image
%
% *A MATLAB movie is an array of FRAME structures, each of
% which contains fields cdata and colormap.
%
% Example:
% % Construct a multimedia reader object associated with file
% % 'xylophone.mp4'.
% readerobj = VideoReader('xylophone.mp4');
%
% % Read in all video frames.
% vidFrames = read(readerobj);
%
% % Get the number of frames.
% numFrames = get(readerobj, 'numberOfFrames');
%
% % Create a MATLAB movie struct from the video frames.
% for k = 1 : numFrames
% mov(k).cdata = vidFrames(:,:,:,k);
% mov(k).colormap = [];
% end
%
% % Create a figure
% hf = figure;
%
% % Resize figure based on the video's width and height
% set(hf, 'position', [150 150 readerobj.Width readerobj.Height])
%
% % Playback movie once at the video's frame rate
% movie(hf, mov, 1, readerobj.FrameRate);
%
% See also AUDIOVIDEO, MOVIE, VIDEOREADER, VIDEOREADER/READFRAME, VIDEOREADER/HASFRAME, MMFILEINFO.
% NCH DTL
% Copyright 2005-2014 The MathWorks, Inc.
if length(obj) > 1
error(message('MATLAB:audiovideo:VideoReader:nonscalar'));
end
% ensure that we pass in 1, 2 or 3 arguments only
narginchk(1, 3);
% ensure that we pass out only 1 output argument
nargoutchk(0, 1);
% Verify that the index argument is of numeric type
if nargin < 2
index = [1 inf];
outputformat = 'default';
elseif nargin < 3 && ischar(index)
outputformat = index;
index = [1 inf];
elseif nargin < 3
outputformat = 'default';
end
validateattributes( ...
index, ...
{'numeric'}, {'vector'}, ...
'VideoReader.read', 'index');
index = double(index);
try
outputformat = VideoReader.validateOutputFormat(outputformat, 'VideoReader.read');
catch ME
throwAsCaller(ME);
end
if obj.IsStreamingBased
error( message('MATLAB:audiovideo:VideoReader:ReadNotAllowed') );
end
warnState = warning('off', 'MATLAB:audiovideo:VideoReader:unknownNumFrames');
oc = onCleanup( @() warning(warnState) );
% Frame-based operations need to know the NumberOfFrames before reading.
% As frame-counting is not performed during object construction, it has to
% be performed before the first call to read.
numFrames = get(obj, 'NumberOfFrames');
try
if nargin == 1
frameIndex = [1 Inf];
% Dimensions of data returned is HxWx3xN
videoFrames = read(getImpl(obj));
elseif nargin >= 2
% Dimensions of data returned is HxWx3xN
videoFrames = read(getImpl(obj), index);
if isscalar(index)
frameIndex = [index index];
else
frameIndex = index;
end
end
catch err
VideoReader.handleImplException(err);
end
% Update the frameIndex only if the total number of frames in the video can
% be determined after the read operation
if( ~isempty( numFrames ) )
frameIndex(frameIndex == Inf) = numFrames;
end
% Check that read was complete only if the frame indices to be read have
% been accurately determined.
if ~any(frameIndex == Inf)
checkIncompleteRead(size(videoFrames, 4), frameIndex);
end
videoFrames = VideoReader.convertToOutputFormat( videoFrames, ...
get(obj, 'VideoFormat'), ...
outputformat, ...
get(getImpl(obj), 'colormap'));
% Video is the output argument.
varargout{1} = videoFrames;
obj.IsFrameBased = true;
end
function checkIncompleteRead(actNum, index)
expNum = index(2) - index(1) + 1;
if actNum < expNum
warning(message('MATLAB:audiovideo:VideoReader:incompleteRead', ...
index(1), index(1)+actNum-1));
end
end