CallbackVideoTexture

Shared base for JVM-side video textures whose source pushes decoded frames from a worker thread (libVLC, FFmpeg, JavaCV, JavaFX MediaView-snapshot, …):

• Subclasses call submitFrame (ByteArray or ByteBuffer) on the decoder thread; the base atomically publishes a fresh FrameBuf to the GL thread — lock-free.

• On every bindTexture (GL thread), if a new frame is pending, the base atomically consumes it via getAndSet(null) and uploads via glTexSubImage2D (or glTexImage2D on first frame / resolution change). With nothing pending the upload is skipped — the driver keeps the previous frame's storage live.

Optimizations vs. a naive blit:

• GL_TEXTURE_SWIZZLE_A = GL_ONE — sampler returns alpha=1.0 regardless of the texture bytes; eliminates a per-frame CPU pass to force every 4th byte to 0xFF.

• glTexSubImage2D for steady-state — re-uploads pixels into existing GPU storage instead of re-allocating with glTexImage2D every frame.

• Optional PBO path (usePbo) — uploads route through GL_PIXEL_UNPACK_BUFFER via glMapBufferRange(... INVALIDATE_BUFFER | UNSYNCHRONIZED) + memcpy + glUnmapBuffer. Driver hands back fresh staging memory directly while the previous transfer is still in flight; fewer driver round-trips than the bufferData(null) + bufferData(data) orphan idiom.

• Lock-free frame publish — no synchronized between decoder and GL threads. Two AtomicReference<FrameBuf> slots (latest + recycled) serve as the producer / consumer queue; at steady state at most two ByteArrays exist in flight.

Internal format is GL_RGBA (which JoglKgl maps to renderable GL_RGBA8); upload pixel-format (uploadFormat) is whatever the decoder produces — GL_BGRA for libVLC RV32, FFmpeg/JavaCV after sws_scale, and JavaFX PixelFormat.byteBgra.

Inheritors