diff --git a/av/audio/codeccontext.py b/av/audio/codeccontext.py
index 8174ba26d..4e7118d34 100644
--- a/av/audio/codeccontext.py
+++ b/av/audio/codeccontext.py
@@ -7,6 +7,7 @@
 from cython.cimports.av.packet import Packet
 
 
+@cython.final
 @cython.cclass
 class AudioCodecContext(CodecContext):
     @cython.cfunc
diff --git a/av/audio/fifo.py b/av/audio/fifo.py
index ebd68adb8..0fd128ee7 100644
--- a/av/audio/fifo.py
+++ b/av/audio/fifo.py
@@ -3,6 +3,7 @@
 from cython.cimports.av.error import err_check
 
 
+@cython.final
 @cython.cclass
 class AudioFifo:
     """A simple audio sample FIFO (First In First Out) buffer."""
diff --git a/av/audio/format.py b/av/audio/format.py
index 97e1b59a2..d398f6924 100644
--- a/av/audio/format.py
+++ b/av/audio/format.py
@@ -20,6 +20,7 @@ def get_audio_format(c_format: lib.AVSampleFormat) -> AudioFormat:
     return format
 
 
+@cython.final
 @cython.cclass
 class AudioFormat:
     """Descriptor of audio formats."""
diff --git a/av/audio/frame.py b/av/audio/frame.py
index 0ff969475..c843c9efd 100644
--- a/av/audio/frame.py
+++ b/av/audio/frame.py
@@ -27,6 +27,7 @@ def alloc_audio_frame() -> AudioFrame:
 }
 
 
+@cython.final
 @cython.cclass
 class AudioFrame(Frame):
     """A frame of audio."""
diff --git a/av/audio/layout.py b/av/audio/layout.py
index e7163e33b..344efa220 100644
--- a/av/audio/layout.py
+++ b/av/audio/layout.py
@@ -25,6 +25,7 @@ def get_audio_layout(c_layout: lib.AVChannelLayout) -> AudioLayout:
     return layout
 
 
+@cython.final
 @cython.cclass
 class AudioLayout:
     def __cinit__(self, layout):
diff --git a/av/audio/plane.py b/av/audio/plane.py
index bdaf15708..e68b5403e 100644
--- a/av/audio/plane.py
+++ b/av/audio/plane.py
@@ -2,6 +2,7 @@
 from cython.cimports.av.audio.frame import AudioFrame
 
 
+@cython.final
 @cython.cclass
 class AudioPlane(Plane):
     def __cinit__(self, frame: AudioFrame, index: cython.int):
diff --git a/av/audio/resampler.py b/av/audio/resampler.py
index b0572607f..fb6d98910 100644
--- a/av/audio/resampler.py
+++ b/av/audio/resampler.py
@@ -6,6 +6,7 @@
 from av.error import FFmpegError
 
 
+@cython.final
 @cython.cclass
 class AudioResampler:
     """AudioResampler(format=None, layout=None, rate=None)
diff --git a/av/audio/stream.py b/av/audio/stream.py
index e32f7f759..38009db19 100644
--- a/av/audio/stream.py
+++ b/av/audio/stream.py
@@ -3,6 +3,7 @@
 from cython.cimports.av.packet import Packet
 
 
+@cython.final
 @cython.cclass
 class AudioStream(Stream):
     def __repr__(self):
diff --git a/av/bitstream.py b/av/bitstream.py
index 3c0bff1bd..db808ab35 100644
--- a/av/bitstream.py
+++ b/av/bitstream.py
@@ -6,6 +6,7 @@
 from cython.cimports.libc.errno import EAGAIN
 
 
+@cython.final
 @cython.cclass
 class BitStreamFilterContext:
     """
diff --git a/av/buffer.py b/av/buffer.py
index 5b179f322..3fefceee4 100644
--- a/av/buffer.py
+++ b/av/buffer.py
@@ -9,6 +9,7 @@
 from cython.cimports.libc.string import memcpy
 
 
+@cython.final
 @cython.cclass
 class ByteSource:
     def __cinit__(self, owner):
diff --git a/av/codec/codec.py b/av/codec/codec.py
index 552af8284..681e8cd1d 100644
--- a/av/codec/codec.py
+++ b/av/codec/codec.py
@@ -59,6 +59,7 @@ class UnknownCodecError(ValueError):
     pass
 
 
+@cython.final
 @cython.cclass
 class Codec:
     """Codec(name, mode='r')
diff --git a/av/codec/hwaccel.py b/av/codec/hwaccel.py
index 0155bdae4..69f742b29 100644
--- a/av/codec/hwaccel.py
+++ b/av/codec/hwaccel.py
@@ -54,6 +54,7 @@ def wrap_hwconfig(ptr: cython.pointer[cython.const[lib.AVCodecHWConfig]]) -> HWC
     return config
 
 
+@cython.final
 @cython.cclass
 class HWConfig:
     def __init__(self, sentinel):
@@ -103,6 +104,7 @@ def hwdevices_available():
     return result
 
 
+@cython.final
 @cython.cclass
 class HWAccel:
     def __init__(
diff --git a/av/container/input.py b/av/container/input.py
index 63792e02a..f5fc52547 100644
--- a/av/container/input.py
+++ b/av/container/input.py
@@ -6,7 +6,7 @@
 from cython.cimports.av.packet import Packet
 from cython.cimports.av.stream import Stream, wrap_stream
 from cython.cimports.av.utils import avdict_to_dict
-from cython.cimports.libc.stdint import int64_t
+from cython.cimports.libc.stdint import int64_t, uint8_t
 from cython.cimports.libc.stdlib import free, malloc
 
 
@@ -20,6 +20,7 @@ def close_input(self: InputContainer):
             self._myflag &= ~2  # enum.input_was_opened = False
 
 
+@cython.final
 @cython.cclass
 class InputContainer(Container):
     def __cinit__(self, *args, **kwargs):
@@ -153,9 +154,9 @@ def demux(self, *args, **kwargs):
         streams: list[Stream] = self.streams.get(*args, **kwargs)
         if self.ptr.nb_streams == 0:
             return
-        include_stream: cython.pointer[cython.bint] = cython.cast(
-            cython.pointer[cython.bint],
-            malloc(self.ptr.nb_streams * cython.sizeof(bint)),
+        include_stream: cython.pointer[uint8_t] = cython.cast(
+            cython.pointer[uint8_t],
+            malloc(self.ptr.nb_streams * cython.sizeof(uint8_t)),
         )
         if include_stream == cython.NULL:
             raise MemoryError()
@@ -168,12 +169,12 @@ def demux(self, *args, **kwargs):
         self.set_timeout(self.read_timeout)
         try:
             for i in range(self.ptr.nb_streams):
-                include_stream[i] = False
+                include_stream[i] = 0
             for stream in streams:
                 i = stream.index
                 if i >= self.ptr.nb_streams:
                     raise ValueError(f"stream index {i} out of range")
-                include_stream[i] = True
+                include_stream[i] = 1
 
             # Pre-allocate a AVPacket that is reused as the read buffer.
             with cython.nogil:
diff --git a/av/container/output.py b/av/container/output.py
index 4e868d60c..239e550f2 100644
--- a/av/container/output.py
+++ b/av/container/output.py
@@ -32,6 +32,7 @@ def close_output(self: OutputContainer):
             self._myflag |= 8  # enum.done = True
 
 
+@cython.final
 @cython.cclass
 class OutputContainer(Container):
     def __cinit__(self, *args, **kwargs):
diff --git a/av/container/pyio.py b/av/container/pyio.py
index 6c248ba13..d5c420ea4 100644
--- a/av/container/pyio.py
+++ b/av/container/pyio.py
@@ -14,6 +14,7 @@
 )
 
 
+@cython.final
 @cython.cclass
 class PyIOFile:
     def __cinit__(self, file, buffer_size, writeable=None):
diff --git a/av/container/streams.py b/av/container/streams.py
index a84e88792..e588694b4 100644
--- a/av/container/streams.py
+++ b/av/container/streams.py
@@ -40,6 +40,7 @@ def _get_best_stream_index(
     return stream_index
 
 
+@cython.final
 @cython.cclass
 class StreamContainer:
     """
diff --git a/av/descriptor.py b/av/descriptor.py
index 20cd1a787..faaa0f57c 100644
--- a/av/descriptor.py
+++ b/av/descriptor.py
@@ -19,6 +19,7 @@ def wrap_avclass(ptr: cython.pointer[cython.const[lib.AVClass]]) -> Descriptor |
     return obj
 
 
+@cython.final
 @cython.cclass
 class Descriptor:
     def __cinit__(self, sentinel):
diff --git a/av/dictionary.py b/av/dictionary.py
index bdd02d055..c9bd76acb 100644
--- a/av/dictionary.py
+++ b/av/dictionary.py
@@ -2,6 +2,7 @@
 from cython.cimports.av.error import err_check
 
 
+@cython.final
 @cython.cclass
 class Dictionary:
     def __cinit__(self, *args, **kwargs):
diff --git a/av/filter/context.py b/av/filter/context.py
index bb2068ae9..4873b3ff5 100644
--- a/av/filter/context.py
+++ b/av/filter/context.py
@@ -24,6 +24,7 @@ def wrap_filter_context(
     return self
 
 
+@cython.final
 @cython.cclass
 class FilterContext:
     def __cinit__(self, sentinel):
diff --git a/av/filter/filter.py b/av/filter/filter.py
index b348dd3e0..bd4d21896 100644
--- a/av/filter/filter.py
+++ b/av/filter/filter.py
@@ -13,6 +13,7 @@ def wrap_filter(ptr: cython.pointer[cython.const[lib.AVFilter]]) -> Filter:
     return filter_
 
 
+@cython.final
 @cython.cclass
 class Filter:
     def __cinit__(self, name):
diff --git a/av/filter/graph.py b/av/filter/graph.py
index 507fbf015..c1b61eb20 100644
--- a/av/filter/graph.py
+++ b/av/filter/graph.py
@@ -12,6 +12,7 @@
 from cython.cimports.av.video.frame import VideoFrame
 
 
+@cython.final
 @cython.cclass
 class Graph:
     def __cinit__(self):
diff --git a/av/filter/link.py b/av/filter/link.py
index 7914ba2b1..09a078d5a 100644
--- a/av/filter/link.py
+++ b/av/filter/link.py
@@ -5,6 +5,7 @@
 _cinit_sentinel = cython.declare(object, object())
 
 
+@cython.final
 @cython.cclass
 class FilterLink:
     def __cinit__(self, sentinel):
@@ -78,6 +79,7 @@ def name(self):
         return lib.avfilter_pad_get_name(self.base_ptr, self.index)
 
 
+@cython.final
 @cython.cclass
 class FilterContextPad(FilterPad):
     def __repr__(self):
diff --git a/av/format.py b/av/format.py
index aad23050d..a8222577b 100644
--- a/av/format.py
+++ b/av/format.py
@@ -46,6 +46,7 @@ class Flags(Flag):
 # fmt: on
 
 
+@cython.final
 @cython.cclass
 class ContainerFormat:
     """Descriptor of a container format.
diff --git a/av/index.py b/av/index.py
index 504da9576..b652bfdc1 100644
--- a/av/index.py
+++ b/av/index.py
@@ -12,6 +12,7 @@ def wrap_index_entry(ptr: cython.pointer[cython.const[lib.AVIndexEntry]]) -> Ind
     return obj
 
 
+@cython.final
 @cython.cclass
 class IndexEntry:
     """A single entry from a stream's index.
@@ -71,6 +72,7 @@ def wrap_index_entries(ptr: cython.pointer[lib.AVStream]) -> IndexEntries:
     return obj
 
 
+@cython.final
 @cython.cclass
 class IndexEntries:
     """A sequence-like view of FFmpeg's per-stream index entries.
diff --git a/av/logging.py b/av/logging.py
index dbd247d56..2b565b9e8 100644
--- a/av/logging.py
+++ b/av/logging.py
@@ -170,6 +170,7 @@ def get_last_error():
 thread_captures = cython.declare(dict, {})
 
 
+@cython.final
 @cython.cclass
 class Capture:
     """A context manager for capturing logs.
diff --git a/av/opaque.py b/av/opaque.py
index bd25fd61f..3a57989e4 100644
--- a/av/opaque.py
+++ b/av/opaque.py
@@ -17,6 +17,7 @@ def key_free(opaque: cython.p_void, data: u8ptr) -> cython.void:
         opaque_container.pop(name)
 
 
+@cython.final
 @cython.cclass
 class OpaqueContainer:
     def __cinit__(self):
diff --git a/av/option.py b/av/option.py
index 6a20af14f..8ed3c8fb1 100644
--- a/av/option.py
+++ b/av/option.py
@@ -124,6 +124,7 @@ def is_filtering_param(self):
         return flag_in_bitfield(self.ptr.flags, lib.AV_OPT_FLAG_FILTERING_PARAM)
 
 
+@cython.final
 @cython.cclass
 class Option(BaseOption):
     @property
@@ -186,6 +187,7 @@ def wrap_option_choice(
     return obj
 
 
+@cython.final
 @cython.cclass
 class OptionChoice(BaseOption):
     """
diff --git a/av/packet.py b/av/packet.py
index b25f61c93..a69cf38c1 100644
--- a/av/packet.py
+++ b/av/packet.py
@@ -65,6 +65,7 @@ def packet_sidedata_type_from_literal(dtype: PktSideDataT) -> lib.AVPacketSideDa
     return get_args(PktSideDataT).index(dtype)
 
 
+@cython.final
 @cython.cclass
 class PacketSideData(Buffer):
     @staticmethod
@@ -207,6 +208,7 @@ def _python_free(
             Py_DECREF(cython.cast(object, opaque))
 
 
+@cython.final
 @cython.cclass
 class Packet(Buffer):
     """A packet of encoded data within a :class:`~av.format.Stream`.
diff --git a/av/sidedata/encparams.py b/av/sidedata/encparams.py
index 399189a6b..d0e78e8a1 100644
--- a/av/sidedata/encparams.py
+++ b/av/sidedata/encparams.py
@@ -13,6 +13,7 @@ class VideoEncParamsType(IntEnum):
     MPEG2 = lib.AV_VIDEO_ENC_PARAMS_MPEG2
 
 
+@cython.final
 @cython.cclass
 class VideoEncParams(SideData):
     def __repr__(self):
@@ -129,6 +130,7 @@ def qp_map(self):
         return map
 
 
+@cython.final
 @cython.cclass
 class VideoBlockParams:
     def __init__(self, video_enc_params: VideoEncParams, idx: cython.int) -> None:
diff --git a/av/sidedata/motionvectors.py b/av/sidedata/motionvectors.py
index dcf0e9913..369832ba6 100644
--- a/av/sidedata/motionvectors.py
+++ b/av/sidedata/motionvectors.py
@@ -6,6 +6,7 @@
 _cinit_bypass_sentinel = cython.declare(object, object())
 
 
+@cython.final
 @cython.cclass
 class MotionVectors(SideData):
     def __init__(self, sentinel, frame: Frame, index: cython.int):
@@ -70,6 +71,7 @@ def to_ndarray(self):
         )
 
 
+@cython.final
 @cython.cclass
 class MotionVector:
     """
diff --git a/av/stream.py b/av/stream.py
index a1a615aae..23749e699 100644
--- a/av/stream.py
+++ b/av/stream.py
@@ -279,6 +279,7 @@ def type(self):
         return "unknown" if media_type == cython.NULL else media_type
 
 
+@cython.final
 @cython.cclass
 class DataStream(Stream):
     def __repr__(self):
@@ -297,6 +298,7 @@ def name(self):
         return desc.name
 
 
+@cython.final
 @cython.cclass
 class AttachmentStream(Stream):
     """
diff --git a/av/subtitles/codeccontext.py b/av/subtitles/codeccontext.py
index c2a9fb4ae..acad69fb7 100644
--- a/av/subtitles/codeccontext.py
+++ b/av/subtitles/codeccontext.py
@@ -9,6 +9,7 @@
 from cython.cimports.libc.string import memcpy
 
 
+@cython.final
 @cython.cclass
 class SubtitleCodecContext(CodecContext):
     @property
diff --git a/av/subtitles/stream.py b/av/subtitles/stream.py
index 525440e9d..484eff5be 100644
--- a/av/subtitles/stream.py
+++ b/av/subtitles/stream.py
@@ -3,6 +3,7 @@
 from cython.cimports.av.stream import Stream
 
 
+@cython.final
 @cython.cclass
 class SubtitleStream(Stream):
     def __getattr__(self, name):
diff --git a/av/subtitles/subtitle.py b/av/subtitles/subtitle.py
index 91a8aa142..24bf8cbe5 100644
--- a/av/subtitles/subtitle.py
+++ b/av/subtitles/subtitle.py
@@ -3,6 +3,7 @@
 from cython.cimports.libc.string import memcpy
 
 
+@cython.final
 @cython.cclass
 class SubtitleProxy:
     def __dealloc__(self):
@@ -12,6 +13,7 @@ def __dealloc__(self):
 _cinit_bypass_sentinel = cython.declare(object, object())
 
 
+@cython.final
 @cython.cclass
 class SubtitleSet:
     """
@@ -204,6 +206,7 @@ def __repr__(self):
         return f"<av.{self.__class__.__name__} at 0x{id(self):x}>"
 
 
+@cython.final
 @cython.cclass
 class BitmapSubtitle(Subtitle):
     def __cinit__(self, subtitle: SubtitleSet, index: cython.int):
@@ -247,6 +250,7 @@ def __getitem__(self, i):
         return self.planes[i]
 
 
+@cython.final
 @cython.cclass
 class BitmapSubtitlePlane:
     def __cinit__(self, subtitle: BitmapSubtitle, index: cython.int):
@@ -265,6 +269,7 @@ def __getbuffer__(self, view: cython.pointer[Py_buffer], flags: cython.int):
         PyBuffer_FillInfo(view, self, self._buffer, self.buffer_size, 0, flags)
 
 
+@cython.final
 @cython.cclass
 class AssSubtitle(Subtitle):
     """
diff --git a/av/video/codeccontext.py b/av/video/codeccontext.py
index c9ac25788..eb1c9a365 100644
--- a/av/video/codeccontext.py
+++ b/av/video/codeccontext.py
@@ -37,6 +37,7 @@ def _get_hw_format(
     )
 
 
+@cython.final
 @cython.cclass
 class VideoCodecContext(CodecContext):
     @cython.cfunc
diff --git a/av/video/format.py b/av/video/format.py
index 4b6291e71..ce2246836 100644
--- a/av/video/format.py
+++ b/av/video/format.py
@@ -27,6 +27,7 @@ def get_pix_fmt(name: cython.p_const_char) -> lib.AVPixelFormat:
     return pix_fmt
 
 
+@cython.final
 @cython.cclass
 class VideoFormat:
     """
@@ -139,6 +140,7 @@ def chroma_height(self, luma_height: cython.int = 0):
         return -((-luma_height) >> self.ptr.log2_chroma_h) if luma_height else 0
 
 
+@cython.final
 @cython.cclass
 class VideoFormatComponent:
     def __cinit__(self, format: VideoFormat, index: cython.size_t):
diff --git a/av/video/frame.py b/av/video/frame.py
index 1f345d365..605ec9a9c 100644
--- a/av/video/frame.py
+++ b/av/video/frame.py
@@ -19,6 +19,7 @@
 from cython.cimports.libc.stdint import int64_t, uint8_t
 
 
+@cython.final
 @cython.cclass
 class CudaContext:
     def __cinit__(self, device_id: cython.int = 0, primary_ctx: cython.bint = True):
@@ -466,6 +467,7 @@ def check_ndarray_shape(array: object, ok: cython.bint):
         raise ValueError(f"Unexpected numpy array shape `{array.shape}`")
 
 
+@cython.final
 @cython.cclass
 class VideoFrame(Frame):
     def __cinit__(self, width=0, height=0, format="yuv420p"):
diff --git a/av/video/plane.py b/av/video/plane.py
index 99c159652..0652f108f 100644
--- a/av/video/plane.py
+++ b/av/video/plane.py
@@ -17,6 +17,7 @@
 from cython.cimports.libc.stdlib import free, malloc
 
 
+@cython.final
 @cython.cclass
 class VideoPlane(Plane):
     def __cinit__(self, frame: VideoFrame, index: cython.int):
diff --git a/av/video/reformatter.py b/av/video/reformatter.py
index 67f4bd0ad..5778711d8 100644
--- a/av/video/reformatter.py
+++ b/av/video/reformatter.py
@@ -141,6 +141,7 @@ def _set_frame_colorspace(
         frame.colorspace = lib.AVCOL_SPC_SMPTE240M
 
 
+@cython.final
 @cython.cclass
 class VideoReformatter:
     """An object for reformatting size and pixel format of :class:`.VideoFrame`.
diff --git a/av/video/stream.py b/av/video/stream.py
index d5b2c106d..c37f45a3e 100644
--- a/av/video/stream.py
+++ b/av/video/stream.py
@@ -5,6 +5,7 @@
 from cython.cimports.av.video.frame import VideoFrame
 
 
+@cython.final
 @cython.cclass
 class VideoStream(Stream):
     def __repr__(self):