diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 2a8d815b7..00b1a7098 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -28,8 +28,8 @@ We are operating with `semantic versioning <https://semver.org>`_.
     - Bug fixes (PATCH) go here. 
     - $CHANGE by :gh-user:`mikeboers` in (:pr:`1`).
 
-v18.1.0 (Unreleased)
---------------------
+v18.1.0
+-------
 
 Features:
 
@@ -39,11 +39,21 @@ Features:
 - Support reusing the thread's current CUDA context via a ``current_ctx`` flag on ``CudaContext`` and ``VideoFrame.from_dlpack``, for interop with libraries like PyTorch that initialize CUDA first by :gh-user:`Yozer` (:pr:`2339`).
 - ``VideoFrame.from_dlpack`` no longer requires restating ``primary_ctx``/``current_ctx`` when passing an explicit ``cuda_context``; the flags are only validated when explicitly given by :gh-user:`WyattBlue`.
 - Support passing an explicit CUDA stream to FFmpeg CUDA operations, including NVENC input and output, via a ``cuda_stream`` parameter on ``CudaContext``; currently limited to logical CUDA device 0 by :gh-user:`Yozer` (:pr:`2360`).
+- Add ``av.AVRational``, an exact rational number stored as two int32s that mirrors FFmpeg's ``AVRational``. ``Codec.frame_rates`` now holds these rather than ``fractions.Fraction``, and every setter that accepts a ``Fraction`` also accepts an ``AVRational``. Unset rational attributes are falsy, so test them with ``if not stream.time_base:`` rather than ``is None`` by :gh-user:`WyattBlue`.
+- Add ``Frame.metadata``, the metadata FFmpeg attaches to a frame, by :gh-user:`WyattBlue`.
+- Add ``CodecContext.level`` by :gh-user:`WyattBlue`.
+- Add ``VideoCodecContext.field_order`` by :gh-user:`WyattBlue`.
 - ``VideoFrame.save`` now forwards keyword arguments to the encoder, letting callers trade file size for speed (e.g. ``pred="none"`` or ``compression_level=1`` for PNG, ``qscale=2`` for JPG) by :gh-user:`WyattBlue`.
+- Add ``InputContainer.start_time_realtime``, the stream's start time in microseconds since the Unix epoch, which RTSP derives from RTCP sender reports, by :gh-user:`WyattBlue` (:issue:`2365`).
 
 Fixes:
 
 - Fix ``VideoFrame.save`` raising ``AttributeError`` when given a ``Path`` rather than a ``str`` by :gh-user:`WyattBlue`.
+- Fix a frame rate assigned to a ``VideoStream`` after ``add_stream`` being dropped from the output; the codec context's frame rate is now copied to the stream before the header is written by :gh-user:`WyattBlue` (:issue:`2301`).
+
+Misc.:
+
+- Support building from source against FFmpeg 9.0 by :gh-user:`WyattBlue`. The binary wheels still ship FFmpeg 8.1.2.
 
 - Prevent crashes and corrupted output when structural codec properties are changed after an output stream has been opened by :gh-user:`WyattBlue`, reported by :gh-user:`oakaigh` (:issue:`2232`).
 - Fix a crash when using a stream that has no ``CodecContext`` (a demuxed stream with no available decoder, such as one from a truncated file, or a stream created by ``add_mux_stream``); decoding now raises ``DecoderNotFoundError``, encoding now raises ``EncoderNotFoundError``, and ``BitStreamFilterContext`` accepts such a stream as ``out_stream`` by :gh-user:`WyattBlue`, reported by :gh-user:`justinrmiller` (:issue:`2344`).
diff --git a/av/about.py b/av/about.py
index c6a8b8ed8..c84c510d7 100644
--- a/av/about.py
+++ b/av/about.py
@@ -1 +1 @@
-__version__ = "18.0.0"
+__version__ = "18.1.0"
diff --git a/av/container/input.py b/av/container/input.py
index 18558126c..2e26ef3e5 100644
--- a/av/container/input.py
+++ b/av/container/input.py
@@ -114,6 +114,20 @@ def start_time(self):
         if self.ptr.start_time != lib.AV_NOPTS_VALUE:
             return self.ptr.start_time
 
+    @property
+    def start_time_realtime(self):
+        """Start time of the stream in real world time, in microseconds since the
+        Unix epoch, or ``None`` if unknown.
+
+        Only a few demuxers know this; RTSP computes it from RTCP sender reports,
+        which is what makes it useful for aligning analytics with a camera's clock.
+
+        Wraps :ffmpeg:`AVFormatContext.start_time_realtime`.
+        """
+        self._assert_open()
+        if self.ptr.start_time_realtime != lib.AV_NOPTS_VALUE:
+            return self.ptr.start_time_realtime
+
     @property
     def duration(self):
         self._assert_open()
diff --git a/av/container/input.pyi b/av/container/input.pyi
index 88dd07d69..caea60b94 100644
--- a/av/container/input.pyi
+++ b/av/container/input.pyi
@@ -14,6 +14,7 @@ from .core import Container
 
 class InputContainer(Container):
     start_time: int
+    start_time_realtime: int | None
     duration: int | None
     bit_rate: int
     size: int
diff --git a/include/avformat.pxd b/include/avformat.pxd
index 9a18e5a9b..920f18d84 100644
--- a/include/avformat.pxd
+++ b/include/avformat.pxd
@@ -151,6 +151,7 @@ cdef extern from "libavformat/avformat.h" nogil:
         AVIOInterruptCB interrupt_callback
         AVDictionary *metadata
         int64_t start_time
+        int64_t start_time_realtime
         int64_t duration
         int64_t bit_rate
         int flags
diff --git a/tests/test_file_probing.py b/tests/test_file_probing.py
index ce04189f9..8997227ae 100644
--- a/tests/test_file_probing.py
+++ b/tests/test_file_probing.py
@@ -18,6 +18,8 @@ def test_container_probing(self) -> None:
         assert self.file.metadata == {}
         assert self.file.size == 207740
         assert self.file.start_time == 1400000
+        # Only RTSP-like inputs carry a wall clock; a plain file has none.
+        assert self.file.start_time_realtime is None
         assert len(self.file.streams) == 1
 
     def test_stream_probing(self) -> None: