Implementing an Effect that looks ahead in the source

Question

Hello all,
I need to create an application which reads from one AVI file, processes each frame with a special effect, and outputs the result to another AVI of the same format. Fairly standard stuff.
I am fairly new to JMF but I think I have the basic methodology right: creating a Processor, and then during the Configured state, adding a new Effect to the Codec chain of the Processors first TrackControl.
The thing I am unsure about is this: the Effect I am programming needs to 'look ahead' in the source i.e. it needs to see frames 1, 2 and 3 before it can write frame 1 of the output.
Does the process(Buffer input, Buffer output) method of Effect is called for each frame of the video, providing a Buffer for each frame at a time? In this case can I buffer the first three frames for myself, and withhold output until the third frame?
Or is process(Buffer input, Buffer output) called once by the Processor, with the in/out buffers represent the entire stream and able to be read and written to 'asynchronously'? In this case, when I use javax.util.BufferToImage to get my actual frames to apply the effect, do successive calls step through the frames, how do I reference specific frames from this context?
I'll stop speculating now - I hope someone can nudge me in the right direction... Thanks very much for any advice.

Answer 1

Hello Darkmoon_UK,
Your problem seems similar to my one.
I want to implement a slow motion effect with jmf. I also read from an avi file.
First thing I hava to ask is, whether your effect simply plays the original video into the new file, if you only add
output.copy(input);
into process()-method.
I dont't know if it is important, but I add the new Effect to the codec chain AFTER ConfiguredCompleteEvent, not during Configured state. And this works (at least simply playing the video works, not my slow motion effect ;-) ).
Next thing is you should insert some System.out.println()s into your process()-method code to discover that it is called several times (for each frame of the video).
I think it is possible to buffer all the frames into an collection out of java.util.* and make a specific variable (int frameCounter) count the frames by calling frameCounter++; at the end of the process()-method. Same effect is using input.getSequenceNumber(), I think. With the help of a Collection of java.util (ArrayList or something else), it should be possible to access any frame out of the video.
Well, I'm also still learning and trying to force JMF to do what I want, not the other way round, as it is at the moment. I hope this little bit of information I gave you could help you solve your problem or at least nudge you in the right direction.
Bye,
sscheer81