Introduce a new BinaryStreamSink that allows reading a stream of encoded bytes

[jleibs]

What

• Resolves: New recording sink for an in-memory binary stream #6241

This effectively combines the guts of FileSink and MemorySink. Like the FileSink, this runs file-encoding on its own thread so that all we need to do when we're ready to read is move out the bytes.

The downside relative to memory_sink is the stream is a singular RRD. You have no way of accessing information about individual messages, draining from the backlog, etc.

This is designed to be as easy as possible to wire into a gradio output stream.

Example usage in a Gradio Component:

@rr.thread_local_stream("rerun_example_live")
def start_stream_direct(state):

    state['streaming'] = True

    cap = cv2.VideoCapture(0)
    frame_nr = 0
    stream = rr.binary_stream()

    while state.get('streaming', False):
        ret, img = cap.read()

        frame_time_ms = cap.get(cv2.CAP_PROP_POS_MSEC)
        if frame_time_ms != 0:
            rr.set_time_nanos("frame_time", int(frame_time_ms * 1_000_000))

        rr.set_time_sequence("frame_nr", frame_nr)
        frame_nr += 1

        print("Processing frame", frame_nr)

        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

        # Log the original image
        rr.log("image/rgb", rr.Image(img).compress())

        # Convert to grayscale
        gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
        rr.log("image/gray", rr.Image(gray).compress())

        # Run the canny edge detector
        canny = cv2.Canny(gray, 50, 200)
        rr.log("image/canny", rr.Image(canny).compress())

        yield stream.read()

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[Wumpf]

Neat utility, seems pretty straight forward

wondering if we should expose this new type of stream to C++ as well, but I reckon we don't have a usecase for it it, so better not to

Requesting changes because I'd love to see the test being automated - if this turns out to be too much work all good from my side

[Wumpf]

nit: I found 3 implementations of this, two of them using crossbeam one using mpsc like you here. I like that you bring balance to the world ;)

[jleibs]

Good enough for FileSink, good enough for me 🤷

[Wumpf]

any harm in just exposing that as a flag on creation right away?

[jleibs]

Mostly that (1) it also applies to every other sink type and (2) I can't come up with a good reason that a user would ever set it to False.

I'd rather introduce them all together in a consistent way if and when we have a compelling use-case.

[Wumpf]

nice work! super cool to have this running on ci