foo.cpp

int frameTexture; // shared

// main thread

// probably need some synchronization between decoding a frame
// on the decoder thread and displaying it on the main
glBindTexture(GL_TEXTURE_2D, frameTexture);
glDrawEverythingForMe(GL_MAGICAL_ENUM, 0xDEADBEEF);

// decode thread

// get secondary context
makeCurrent();

// switching between two PBOs will make it double buffered,
// and consume 2x space

while ((data = decode(foo)) != null) {
    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pbo);
        byte *ptr = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, ...);
            glBufferData(..., data);
        glUnmapBuffer (GL_PIXEL_UNPACK_BUFFER);
    
        glBindTexture(GL_TEXTURE_2D, frameTexture);
        glTexSubImage2D (GL_TEXTURE_2D, ..., (void *) 0);
    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
}