[osg-users] osg::Image::update?

Hartmut Seichter lists at technotecture.com
Sat Jul 26 19:17:32 PDT 2008

Robert Osfield wrote:
> Hi Hartmut,
> On Sat, Jul 26, 2008 at 2:02 AM, Hartmut Seichter
> <lists at technotecture.com> wrote:
>> Well, osgART has a number of PlugIns implementing their own
>> osgART::VideoImageStream which implements update slightly
>> different. But I am happy to quickly change things over as we are targeting
>> the latest OSG
> For 2.6 all original ImageStream implementation - the ones in the
> Quicktime and Xine plugins are all exactly the same as before, and
> function in exactly the same way.  osgArt::VideoImageStream should be
> no different - all existing mechanisms will work.
> The new Image::update(..) method is only called if you attach an
> update callback to the texture, this is something that is now done
> automatically for osg::ImageSequence images being assigned to
> textures, but not for any other Image types.  You could add this is
> you so wished.
That was exactly what we did with osgART ... we attached a 
osgART::ImageUpdateCallback in order to trigger the update. I think I 
will dive more into ImageStream and ImageSequence to see if we can get 
rid of our (osgART) additional implementation.

>> Are there any plans to differentiate between open() and play() ... this was
>> the main reason for us  to have osgART::VideoImageStream as we need to know
>> in osgART which dimensions and colorspace the imagestream supports
> I haven't made any other plans for ImageStream.  ImageSequence is just
> a subclass of it at present.  The osgDB::ImagePager is a companion to
> it, which could expand in its role - for instance it could potentially
> drive the various ImageStream classes, so rather than have their own
> threads, they'd use the ImagePager's ImageThreads to drive them.  This
> would help when handling many video streams at one time, and also
> improve the handling of thread cancellation on exit.

Yes, that is one area where we have some additional logic in VideoStream 
to deal with threading issues like locking, or double buffering. As I 
said before I need to take a deeper look ImageSequence and the 
ImagePager which might solve a lot of problems for us already.


> Robert.
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Hartmut Seichter, PhD (HKU), Dipl-Ing.(BUW), Postdoctoral Fellow, HITLabNZ

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