Android MediaMuxer with openGL

Question

I am trying to generate movie using MediaMuxer. The Grafika example is an excellent effort, but when i try to extend it, I have some problems.

I am trying to draw some basic shapes like square, triangle, lines into the Movie. My openGL code works well if I draw the shapes into the screen but I couldn't draw the same shapes into the video.

I also have questions about setting up openGL matrix, program, shader and viewport. Normally, there are methods like onSurfaceCreated and onSurfaceChanged so that I can setup these things. What is the best way to do it in GeneratedMovie?

Anybody has examples of writing into video with more complicated shapes would be welcome

Answer 1

The complexity of what you're drawing shouldn't matter. You draw whatever you're going to draw, then call eglSwapBuffers() to submit the buffer. Whether you draw one flat-shaded triangle or 100K super-duper-shaded triangles, you're still just submitting a buffer of data to the video encoder or the surface compositor.

There is no equivalent to SurfaceView's surfaceCreated() and surfaceChanged(), because the Surface is created by MediaCodec#createInputSurface() (so you know when it's created), and the Surface does not change.

The code that uses GeneratedMovie does some fairly trivial rendering (set scissor rect, call clear). The code in RecordFBOActivity is what you should probably be looking at -- it has a bouncing rect and a spinning triangle, and demonstrates three different ways to deal with the fact that you have to render twice.

(The code in HardwareScalerActivity uses the same GLES routines and demonstrates texturing, but it doesn't do recording.)

The key thing is to manage your EGLContext and EGLSurfaces carefully. The various bits of GLES state are held in the EGLContext, which can be current on only one thread at a time. It's easiest to use a single context and set up a separate EGLSurface for each Surface, but you can also create separate contexts (with or without sharing) and switch between them.

Some additional background material is available here.