Share AudioFrame plane count with AudioPlane

av/audio/frame.pxd

@@ -27,5 +27,6 @@ cdef class AudioFrame(Frame):
 
     cdef void _init(self, lib.AVSampleFormat format, lib.AVChannelLayout layout, unsigned int nb_samples, unsigned int align)
     cdef void _init_user_attributes(self)
+    cdef int _nb_planes(self)
 
 cdef AudioFrame alloc_audio_frame()

av/audio/frame.py

@@ -141,14 +141,18 @@ def from_ndarray(array, format="s16", layout="stereo"):
             plane.update(array[i, :])
         return frame
 
+    @cython.cfunc
+    def _nb_planes(self) -> cython.int:
+        return self.layout.nb_channels if self.format.is_planar else 1
+
     @property
     def planes(self):
         """
         A tuple of :class:`~av.audio.plane.AudioPlane`.
 
         :type: tuple
         """
-        nb_planes: cython.int = self.layout.nb_channels if self.format.is_planar else 1
+        nb_planes: cython.int = self._nb_planes()
         plane_count: cython.int = 0
         while plane_count < nb_planes and self.ptr.extended_data[plane_count]:
             plane_count += 1

av/audio/plane.py

@@ -6,9 +6,7 @@
 @cython.cclass
 class AudioPlane(Plane):
     def __cinit__(self, frame: AudioFrame, index: cython.int):
-        nb_planes: cython.int = (
-            frame.layout.nb_channels if frame.format.is_planar else 1
-        )
+        nb_planes: cython.int = frame._nb_planes()
         if index < 0 or index >= nb_planes:
             raise ValueError(f"plane index {index} out of range for {nb_planes} planes")
 

tests/test_audioframe.py

@@ -56,6 +56,17 @@ def test_manual_fltp_7_1_constructor() -> None:
     assertNdarraysEqual(frame.to_ndarray(), array)
 
 
+def test_manual_fltp_22_2_constructor() -> None:
+    # More than 8 planes: extended_data is a separate heap array of exactly
+    # nb_channels pointers, so reading past it would be out of bounds.
+    frame = AudioFrame(format="fltp", layout="22.2", samples=160)
+    assert len(frame.planes) == 24
+
+    array = np.arange(24 * 160, dtype="f4").reshape(24, 160)
+    frame = AudioFrame.from_ndarray(array, format="fltp", layout="22.2")
+    assertNdarraysEqual(frame.to_ndarray(), array)
+
+
 def test_manual_s16_mono_constructor() -> None:
     frame = AudioFrame(format="s16", layout="mono", samples=160)
     assert frame.format.name == "s16"