bits_per_coded_sample: wrote tests, changed docstring, and created wa…

…rning

av/video/codeccontext.pyx

@@ -100,15 +100,24 @@ cdef class VideoCodecContext(CodecContext):
     @property
     def bits_per_coded_sample(self):
         """
-        The number of bits per sample in the codedwords, basically the bitrate per sample. 
-        It is mandatory for this to be set for some formats to decode them.
+        bits per sample/pixel from the demuxer (needed for huffyuv).
+
+            encoding: Set by libavcodec.
+            decoding: Set by user.
+
+         Wraps :ffmpeg:`AVCodecContext::bits_per_coded_sample`
         
         :type: int
         """
         return self.ptr.bits_per_coded_sample
 
     @bits_per_coded_sample.setter
     def bits_per_coded_sample(self, int value):
+        if self.is_encoder:
+            warnings.warn(
+                "Setting VideoCodecContext.bits_per_coded_sample for encoders is deprecated.",
+                AVDeprecationWarning
+            )
         self.ptr.bits_per_coded_sample = value
         self._build_format()
 

tests/test_codec_context.py

@@ -174,6 +174,38 @@ def _assert_parse(self, codec_name, path):
             self.assertEqual(len(parsed_source), len(full_source))
             self.assertEqual(full_source, parsed_source)
 
+    def test_bits_per_coded_sample(self):
+        with av.open(fate_suite("qtrle/aletrek-rle.mov")) as container:
+            stream = container.streams.video[0]
+            stream.codec_context.bits_per_coded_sample = 32
+
+            for packet in container.demux(stream):
+                for frame in packet.decode():
+                    pass
+                self.assertEqual(packet.stream.codec_context.bits_per_coded_sample, 32)
+
+        with av.open(fate_suite("qtrle/aletrek-rle.mov")) as container:
+            stream = container.streams.video[0]
+            stream.codec_context.bits_per_coded_sample = 31
+
+            with self.assertRaises(av.error.InvalidDataError):
+                for packet in container.demux(stream):
+                    for frame in packet.decode():
+                        pass
+                    self.assertEqual(
+                        packet.stream.codec_context.bits_per_coded_sample, 31
+                    )
+
+        with av.open(self.sandboxed("output.mov"), "w") as output:
+            stream = output.add_stream("qtrle")
+
+            with warnings.catch_warnings(record=True) as captured:
+                stream.codec_context.bits_per_coded_sample = 32
+                self.assertEqual(
+                    captured[0].message.args[0],
+                    "Setting VideoCodecContext.bits_per_coded_sample for encoders is deprecated.",
+                )
+
 
 class TestEncoding(TestCase):
     def test_encoding_png(self):