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getinfo

PURPOSE ^

INFO=GETINFO(VR)

SYNOPSIS ^

function info = getinfo(vr)

DESCRIPTION ^

INFO=GETINFO(VR)
  Returns a structure whose fields contain information about the opened
  video object.  The (minimum) set of fields in the INFO structure is
  shown below:
    url        String specifying the data source, in the format preferred
               by the plugin being used.  Sometimes this will be a true
               URL, sometimes it will be a filename.

    fps        Non-negative number indicating the number of frames per
               second.  

    height     Integer indicating the height of the video frames in
               pixels.   

    width      Integer indicating the width of the video frames in pixels.

    numFrames  Integer indicating an estimate of the total number of 
               frames in the video.  For typical videos, this number is
               exact.  Users may attempt to read more than numFrames
               frames at their own risk.  If nHiddenFinalFrames is
               non-zero, this will typically fail (meaning next/step/seek
               will return 0) or worse, corrupted data such as an
               all-black frame may be returned by the codec.  Some plugins
               and/or their codecs do not supply this information.  If the
               number of frames is unknown, a negative number is returned.
               Older ffmpeg versions (notably version 0.4.9-pre1) do not
               supply this number.

    fourcc     4- or fewer-character string roughly indicating the codec
               used encode the video.  See http://www.fourcc.org for
               additional background information and an extensive, but
               non-comprehensive list of FourCC codes.

    nHiddenFinalFrames
               Non-negative integer.  Many codecs make it difficult or 
               impossible to read the last few frames of a file.  When 
               videoReader thinks that the last few cannot be read, it 
               automatically guesses how many frames cannot be read,
               records this number as nHiddenFinalFrames, and sets
               numFrames to be the number of frames the file claims to
               contain minus nHiddenFinalFrames.  An individual
               videoReader plugin (like the ffmpegPopen2 plugin) may choose
               to allow the user to try reading the frames that might be
               hidden or it may choose not to allow even trying to read
               them (like the DirectShow plugin).

  Due to limitations in some file formats, it is not always possible to
  determine all of these values (or sometimes they are not constant).  In
  these cases, numerical values are given a value of NaN and string values
  are blank.

SEE ALSO
  videoReader

Copyright (c) 2006 Gerald Dalley
See "MIT.txt" in the installation directory for licensing details (especially
when using this library on GNU/Linux).

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function info = getinfo(vr)
0002 %INFO=GETINFO(VR)
0003 %  Returns a structure whose fields contain information about the opened
0004 %  video object.  The (minimum) set of fields in the INFO structure is
0005 %  shown below:
0006 %    url        String specifying the data source, in the format preferred
0007 %               by the plugin being used.  Sometimes this will be a true
0008 %               URL, sometimes it will be a filename.
0009 %
0010 %    fps        Non-negative number indicating the number of frames per
0011 %               second.
0012 %
0013 %    height     Integer indicating the height of the video frames in
0014 %               pixels.
0015 %
0016 %    width      Integer indicating the width of the video frames in pixels.
0017 %
0018 %    numFrames  Integer indicating an estimate of the total number of
0019 %               frames in the video.  For typical videos, this number is
0020 %               exact.  Users may attempt to read more than numFrames
0021 %               frames at their own risk.  If nHiddenFinalFrames is
0022 %               non-zero, this will typically fail (meaning next/step/seek
0023 %               will return 0) or worse, corrupted data such as an
0024 %               all-black frame may be returned by the codec.  Some plugins
0025 %               and/or their codecs do not supply this information.  If the
0026 %               number of frames is unknown, a negative number is returned.
0027 %               Older ffmpeg versions (notably version 0.4.9-pre1) do not
0028 %               supply this number.
0029 %
0030 %    fourcc     4- or fewer-character string roughly indicating the codec
0031 %               used encode the video.  See http://www.fourcc.org for
0032 %               additional background information and an extensive, but
0033 %               non-comprehensive list of FourCC codes.
0034 %
0035 %    nHiddenFinalFrames
0036 %               Non-negative integer.  Many codecs make it difficult or
0037 %               impossible to read the last few frames of a file.  When
0038 %               videoReader thinks that the last few cannot be read, it
0039 %               automatically guesses how many frames cannot be read,
0040 %               records this number as nHiddenFinalFrames, and sets
0041 %               numFrames to be the number of frames the file claims to
0042 %               contain minus nHiddenFinalFrames.  An individual
0043 %               videoReader plugin (like the ffmpegPopen2 plugin) may choose
0044 %               to allow the user to try reading the frames that might be
0045 %               hidden or it may choose not to allow even trying to read
0046 %               them (like the DirectShow plugin).
0047 %
0048 %  Due to limitations in some file formats, it is not always possible to
0049 %  determine all of these values (or sometimes they are not constant).  In
0050 %  these cases, numerical values are given a value of NaN and string values
0051 %  are blank.
0052 %
0053 %SEE ALSO
0054 %  videoReader
0055 %
0056 %Copyright (c) 2006 Gerald Dalley
0057 %See "MIT.txt" in the installation directory for licensing details (especially
0058 %when using this library on GNU/Linux).
0059 
0060 %info = feval(vr.plugin, 'getinfo', vr.handle);
0061 
0062 [names, vals] = feval(vr.plugin, 'getinfo', vr.handle);
0063 info = cell2struct({vals{:}}, {names{:}}, 2);

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