diff --git a/sleap/io/video.py b/sleap/io/video.py
index e1d338229..887075ddb 100644
--- a/sleap/io/video.py
+++ b/sleap/io/video.py
@@ -492,9 +492,16 @@ def __attrs_post_init__(self):
         else:
             self.__data = None
 
+    def set_video_ndarray(self, data: np.ndarray):
+        self.__data = data
+
     # The properties and methods below complete our contract with the
     # higher level Video interface.
 
+    @property
+    def test_frame(self):
+        return self.get_frame(0)
+
     def matches(self, other: "NumpyVideo") -> np.ndarray:
         """
         Check if attributes match those of another video.
diff --git a/sleap/message.py b/sleap/message.py
new file mode 100644
index 000000000..ee358cf64
--- /dev/null
+++ b/sleap/message.py
@@ -0,0 +1,262 @@
+"""
+Module with classes for sending and receiving messages between processes.
+
+These use ZMQ pub/sub sockets.
+
+Most of the time you'll want the PairedSender and PairedReceiver.
+These support a "handshake" to confirm connection. Without an initial
+handshake there's a good chance early messages will be dropped.
+
+Each message is either dictionary or dictionary + numpy ndarray.
+"""
+import attr
+import jsonpickle
+import numpy as np
+import time
+import zmq
+
+from typing import Any, Callable, List, Optional, Text
+
+
+@attr.s(auto_attribs=True)
+class BaseMessageParticipant:
+    """Base class for simple Sender and Receiver."""
+    address: Text = "tcp://127.0.0.1:9001"
+    context: Optional[zmq.Context] = None
+    _socket: Optional[zmq.Socket] = None
+
+    def __attrs_post_init__(self):
+        if self.context is None:
+            self._owns_context = True
+            self.context = zmq.Context()
+        else:
+            self._owns_context = False
+
+    def __del__(self):
+        if self._owns_context and self.context is not None:
+            self.context.term()
+
+
+@attr.s(auto_attribs=True)
+class Receiver(BaseMessageParticipant):
+    """Receives messages from corresponding Sender."""
+
+    _message_queue: List[Any] = attr.ib(factory=list)
+
+    def setup(self):
+        self._socket = self.context.socket(zmq.SUB)
+        self._socket.subscribe("")
+        self._socket.bind(self.address)
+
+    def __del__(self):
+        if self._socket is not None:
+            self._socket.unbind(self._socket.LAST_ENDPOINT)
+            self._socket.close()
+            self._socket = None
+
+    def push_back_message(self, message):
+        """Act like we didn't receive this message yet."""
+        self._message_queue.append(message)
+
+    def _recv(self, flags=0, copy=True, track=False):
+        json_message = self._socket.recv_json(flags=flags)
+
+        if "dtype" in json_message and "shape" in json_message:
+            msg = self._socket.recv(flags=flags, copy=copy, track=track)
+            buf = memoryview(msg)
+            A = np.frombuffer(buf, dtype=json_message["dtype"]).reshape(
+                json_message["shape"]
+            )
+            json_message["ndarray"] = A
+
+        return json_message
+
+    def check_message(self, timeout: int = 10, fresh: bool = False) -> Any:
+        """Attempt to receive a single message."""
+        if self._message_queue and not fresh:
+            return self._message_queue.pop(0)
+
+        if self._socket is None:
+            self.setup()
+
+        if self._socket and self._socket.poll(timeout, zmq.POLLIN):
+            return self._recv()
+        else:
+            return None
+
+    def check_messages(self, timeout: int = 10, times_to_check: int = 10) -> List[dict]:
+        """
+        Attempt to receive multiple messages.
+        
+        This method allows us to keep up with the messages by getting
+        multiple messages that have been sent since the last check.
+        It keeps checking until limit is reached *or* we check without
+        getting any messages back.
+        """
+        messages = []
+
+        # keep looping until we don't receive a message or have checked enough times
+        while True:
+            this_message = self.check_message(timeout)
+
+            # if we didn't get a message, we're done checking
+            if this_message is None:
+                return messages
+
+            # we got a message so add it to list
+            messages.append(this_message)
+
+            # if we've checked enough times, we're done checking
+            if times_to_check <= 0:
+                return messages
+
+            # count down the number of times to check for messages
+            times_to_check -= 1
+
+
+@attr.s(auto_attribs=True)
+class Sender(BaseMessageParticipant):
+    """Publishes messages to corresponding Receiver."""
+
+    def setup(self):
+        self._socket = self.context.socket(zmq.PUB)
+        self._socket.connect(self.address)
+
+    def __del__(self):
+        self._socket.setsockopt(zmq.LINGER, 0)
+        self._socket.close()
+        super().__del__()
+
+    def send_dict(self, data: dict):
+        """Sends dictionary."""
+        if self._socket is None:
+            self.setup()
+        self._socket.send_json(data)
+
+    def send_array(
+        self, header_data: dict, A: np.ndarray, flags=0, copy=True, track=False
+    ):
+        """Sends dictionary + numpy ndarray."""
+        if self._socket is None:
+            self.setup()
+        
+        header_data["dtype"] = str(A.dtype)
+        header_data["shape"] = A.shape
+
+        self._socket.send_json(header_data, flags | zmq.SNDMORE)
+        return self._socket.send(A, flags, copy=copy, track=track)
+
+
+@attr.s(auto_attribs=True)
+class PairedMessageParticipant:
+    sender_address: Text
+    receiver_address: Text
+    context: Optional[zmq.Context] = None
+
+    @classmethod
+    def from_tcp_ports(cls, send_port, rec_port):
+        sender_address = f"tcp://127.0.0.1:{send_port}"
+        receiver_address = f"tcp://127.0.0.1:{rec_port}"
+
+        return cls(sender_address=sender_address, receiver_address=receiver_address)
+
+    def setup(self):
+        self._sender = Sender(address=self.sender_address, context=self.context)
+        self._receiver = Receiver(address=self.receiver_address, context=self.context)
+        self._sender.setup()
+        self._receiver.setup()
+
+    def close(self):
+        if hasattr(self, "_sender"):
+            del self._sender
+        if hasattr(self, "_receiver"):
+            del self._receiver
+
+
+@attr.s(auto_attribs=True)
+class PairedSender(PairedMessageParticipant):
+    connected: bool = False
+
+    @classmethod
+    def from_defaults(cls):
+        return cls.from_tcp_ports(9001, 9002)
+
+    def send_handshake(self, timeout_sec=30):
+        """Send handshake until we get reply."""
+        wait_till = time.time() + timeout_sec
+        while time.time() < wait_till:
+            self._sender.send_dict(dict(type="handshake request"))
+            reply = self._receiver.check_message()
+            if self._is_handshake_reply(reply):
+                return True
+            else:
+                # currently we drop replies until handshake is acknowledged
+                pass
+            time.sleep(0.1)
+        return False
+
+    def _is_handshake_reply(self, message: Any) -> bool:
+        if message:
+            return message.get("type", "") == "handshake reply"
+        return False
+
+    def send_dict(self, *args, **kwargs):
+        self._sender.send_dict(*args, **kwargs)
+
+    def send_array(self, *args, **kwargs):
+        self._sender.send_array(*args, **kwargs)
+
+
+@attr.s(auto_attribs=True)
+class PairedReceiver(PairedMessageParticipant):
+    connected: bool = False
+
+    @classmethod
+    def from_defaults(cls):
+        return cls.from_tcp_ports(9002, 9001)
+
+    def receive_handshake(self, timeout_sec=30):
+        """Waits to receive and acknowledge handshake message."""
+        wait_till = time.time() + timeout_sec
+        while time.time() < wait_till and not self.connected:
+            message = self._receiver.check_message(fresh=True)
+
+            if message is None:
+                continue
+            if self._is_handshake(message):
+                self._respond_to_handshake()
+                return True
+            else:
+                self._receiver.push_back_message(message)
+                return True
+        return False
+
+    def _respond_to_handshake(self):
+        self._sender.send_dict(dict(type="handshake reply"))
+        self.connected = True
+
+    def _is_handshake(self, message: Any):
+        if message:
+            return message.get("type", "") == "handshake request"
+        return False
+
+    def check_messages(self, ack_handshakes: bool = True, *args, **kwargs):
+        """
+        Checks for messages.
+
+        Args:
+            ack_handshakes: If True, then any handshake messages are
+                acknowledged and aren't included in return results
+
+        Results:
+            List of messages, possibly excluding any handshake requests.
+        """
+        messages = self._receiver.check_messages(*args, **kwargs)
+
+        if ack_handshakes:
+            non_handshakes = [m for m in messages if not self._is_handshake(m)]
+            if len(non_handshakes) < len(messages):
+                self._respond_to_handshake()
+                messages = non_handshakes
+
+        return messages
diff --git a/sleap/nn/data/pipelines.py b/sleap/nn/data/pipelines.py
index 5e089cd01..0f70df19d 100644
--- a/sleap/nn/data/pipelines.py
+++ b/sleap/nn/data/pipelines.py
@@ -7,9 +7,12 @@
 well as to define training vs inference versions based on the same configurations.
 """
 
+
 import tensorflow as tf
 import numpy as np
 import attr
+import logging
+import time
 from typing import Sequence, Text, Optional, List, Tuple, Union, TypeVar, Dict
 
 import sleap
@@ -91,6 +94,9 @@
 Transformer = TypeVar("Transformer", *TRANSFORMERS)
 
 
+logger = logging.getLogger(__name__)
+
+
 @attr.s(auto_attribs=True)
 class Pipeline:
     """Pipeline composed of providers and transformers.
@@ -265,7 +271,9 @@ def make_dataset(self) -> tf.data.Dataset:
 
         # Apply transformers.
         for transformer in self.transformers:
+            # t0 = time.time()
             ds = transformer.transform_dataset(ds)
+            # logger.debug(f"{transformer.__class__.__name__}:\t\t{time.time() - t0}")
 
         return ds
 
diff --git a/tests/io/test_video.py b/tests/io/test_video.py
index 00ed4a9d1..7813aa3ab 100644
--- a/tests/io/test_video.py
+++ b/tests/io/test_video.py
@@ -366,10 +366,19 @@ def test_safe_frame_loading(small_robot_mp4_vid):
     assert len(frames) == 2
 
 
+def test_numpy_video_backend():
+    vid = Video.from_numpy(np.zeros((1, 2, 3, 1)))
+    assert vid.test_frame.shape == (2, 3, 1)
+
+    vid.backend.set_video_ndarray(np.ones((2, 3, 4, 1)))
+    assert vid.get_frame(1).shape == (3, 4, 1)
+
+
 def test_safe_frame_loading_all_invalid():
     vid = Video.from_filename("video_that_does_not_exist.mp4")
 
     idxs, frames = vid.get_frames_safely(list(range(10)))
 
     assert idxs == []
-    assert frames is None
\ No newline at end of file
+    assert frames is None
+
diff --git a/tests/test_message.py b/tests/test_message.py
new file mode 100644
index 000000000..7351b6a89
--- /dev/null
+++ b/tests/test_message.py
@@ -0,0 +1,55 @@
+from sleap.message import PairedSender, PairedReceiver
+import time
+
+
+def run_send():
+    from time import sleep
+
+    sender = PairedSender.from_defaults()
+
+    sender.setup()
+    success = sender.send_handshake()
+
+    # Make sure handshake was successful
+    assert success
+
+    # Send 10 messages
+    for i in range(10):
+        sender.send_dict(dict(message_id=i))
+
+    sender.close()
+
+
+def run_receive():
+    receiver = PairedReceiver.from_defaults()
+    receiver.setup()
+
+    success = receiver.receive_handshake()
+
+    # Make sure handshake was succesful
+    assert success
+
+    messages = []
+
+    # Keep checking messages for up to 5 seconds (or until we got last)
+    until = time.time() + 5
+    while time.time() < until:
+        messages.extend(receiver.check_messages(timeout=30, times_to_check=20))
+        if messages and messages[-1]["message_id"] == 9:
+            break
+
+    # Make sure we got all the messages
+    assert len(messages) == 10
+    assert messages[-1]["message_id"] == 9
+
+    receiver.close()
+
+
+def test_send_receive_pair():
+    from multiprocessing import Process
+
+    # run "sender" in a separate process
+    Process(target=run_send).start()
+
+    # receive messages in the main process
+    run_receive()