Well, basically it comes down to this line:
Code:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
That is the only OpenGL related thing needed to know, rest comes down to getting the data out, frame by frame. I would imagine you don't need SDL for this at all, i guess SDL reads the data from the library same way. It would be unnecessary and step that would slow down the rendering.

data is simply pointer to array containing R,G,B bytes per pixel. If you could for example draw a frame in given time to Bitmap/DIB you would be able to read the pixeldata. It's what the tutorial does.