From help-request at octave dot org Sat Oct  1 11:48:12 2005
Subject: Re: software for manipulating AVI files
From: Stefan van der Walt <stefan at sun dot ac dot za>
To: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
Cc: octave help mailing list <help at octave dot org>
Date: Sat, 1 Oct 2005 18:45:43 +0200

On Thu, Sep 29, 2005 at 12:36:37PM -0400, John W. Eaton wrote:
> Does anyone here know of any good free software (GPL compatible
> license required) for manipulating AVI files?  I'd like to be able to
> implement the at least the following AVI functions in Octave:
> 
>   addframe  Add frame to AVI file
>   avifile   Create new AVI file
>   aviinfo   Return information about AVI file
>   aviread   Read AVI file
>   close     Close AVI file

My previous email pointed to the FFMpeg wrapper at
http://www.dsp.sun.ac.za/~stefan, but didn't give any further detail.

For those interested, here are the docstrings of the functions
mentioned above.

 -- Loadable Function:  addframe (AVI, IMAGE)
     Add a frame to an AVI file.

     AVI is created using `avifile'.  IMAGE must be of class `double'
     and scaled to be in [0-1].

See also: avifile, aviread, aviinfo.

 -- Loadable Function: F = avifile (FILENAME, [PARAMETER, VALUE, ...])
 -- Loadable Function: avifile ("codecs")
     Create an AVI-format video file.

     The supported parameters are

    `"compression"' or `"codec"'
          The type of encoder used (default: `"msmpeg4v2"')

    `"fps"'
          Encoding frame rate per second (default: `25.0')

    `"gop"'
          Group-of-pictures - the number of frames after which a
          keyframe is inserted (default: `10')

    `"bitrate"'
          Encoding bitrate (default: `400000')

     To see a list of the available codecs, do `avifile("codecs")'.

See also: addframe, aviinfo, aviread.

 -- Loadable Function: INFO = aviinfo (FILENAME)
     Return the properties of an AVI file.

See also: avifile, aviread, addframe.

 -- Loadable Function: IMAGE = aviread (FILENAME, N)
     Load frame N from the AVI file FILENAME.

See also: avifile, aviinfo, addframe.

Here is an example snippet that utilises the wrapper:

# ----------------------------------------------
# Open the AVI file
m = avifile("test.avi", "codec", "msmpeg4v2")

# Generate and add frames
for i = 1:100
  I = zeros(100,100);
  I(i,:) = i;
  I(:,i) = 200-i;
  addframe(m, I/255)
  printf(".")
endfor
printf("\n")

# Close the file
clear m
# ----------------------------------------------

Regards
Stéfan



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