Re: [Fmj-devel] Drone software and FrameGrabbingControl

[JS <js...@dr...>]

Hi Ken,

Sorry, I have been in quite a hurry. Now back to production, still
interested in fixing this frame grabbing control. There are two places
where it needs a fix: for a VideoCamera and for a MovieReader class.
Let's look first at the MovieReader class that is supposed to read a
movie from a file and, each time its fire() method is called, will
either skip one frame or seek to a particular frame (depending on an
option "isFrameBased") and output it.

It uses a FramePositioningControl and a FrameGrabbingControl. Here is a
snippet of the code where they are initialized:


+++++++++
        _framePositioningControl = (FramePositioningControl) _player
        .getControl("javax.media.control.FramePositioningControl");
...
        _frameGrabbingControl = (FrameGrabbingControl) _player
        .getControl("javax.media.control.FrameGrabbingControl");
+++++++++

And here one where the position is read from the input and the "_frame"
variable is set.

+++++++++
    protected boolean _updateFrameTime(ScalarToken inputToken) throws
IllegalActionException {
        if (_playerOpen == false) {
            _dataSource.disconnect();
            return false;
        } else {
            try {
                if (_isFrameBased) {
                    // frame based
                    int frameNo = inputToken.intValue();
                    if (frameNo < 0)
                        // default: skip to next frame
                        _framePositioningControl.skip(1);
                    else
                        _framePositioningControl.seek(frameNo);
                } else {
                    // time based
                    double mediaTimeDouble = inputToken.doubleValue();
                    Time mediaTime;
                    if (mediaTimeDouble < 0) {
                        mediaTime = new
Time(getDirector().getModelTime().getDoubleValue());
                    } else {
                        mediaTime = new Time(mediaTimeDouble);
                    }
                    // FIXME: if mediaTimeDouble < 0 there is a much
more efficient way to
                    // do this by skipping a number of frames

_framePositioningControl.seek(_framePositioningControl.mapTimeToFrame(mediaTime));
                }
                _frame = _frameGrabbingControl.grabFrame();
            } catch (Exception ex) {
                throw new IllegalActionException(this, ex, "Problem in
call to postfire().");
            }
            return true;
        }
    }
+++++++++

The VideoCamera class has a similar approach. I guess I have to subclass
the javax.media.control.FrameGrabbingControl and
javax.media.control.FramePositioningControl classes somewhere and attach
them to the different readers, but I really don't know where to start.

Thanks for your help.

J.S.


Ken Larson wrote:
> JS -
>
> That's great that you are interested in helping out, I'll do what I
> can to help you help us.
>
> Perhaps you could send example source or a code snippet which shows
> what you are trying to do with the frame grabbing control (how you are
> finding/accessing/using it primarily), and I can give you some ideas
> of places to look.
>
> Our video renderers do implement frame grabbing control, but I don't
> believe that has been tested yet.
>
> Ken
>
> JS wrote:
>> Hi,
>>
>> I am developing an free software (GPL) in Java targeted for interactive
>> art installations and eventually performances (http://drone.ws). I have
>> a mixed background as a programmer and as media artist. I am currently
>> working on several projects, most of which include video and audio. The
>> basic thing I need for now is a stable and performing library for media
>> which would allow me to read, transform (filters) and playback audio and
>> video.
>>
>> I have started using FMJ recently and was really impressed, in
>> particular the integration with lti-civil, the only library with which I
>> was able to read my webcam's input on OS X. However, the
>> FrameGrabbingControl was not working on FMJ so I had to (temporarily)
>> bypass it and use LTI civil. I would like to contribute to the FMJ
>> project in several ways, but let's say I could start by implementing the
>> FrameGrabbingControl. I am not sure where to start, however, I've digged
>> pretty deep into the code but still wasn't sure. If people on this list
>> could give me some advice, that would be welcome. Otherwise I'll jsut go
>> on digging and ask more precise questions.
>>
>> Cheers,
>>
>>   
>


-- 
J. S. Senécal
http://drone.ws