[tests] use "h264" instead of "libx264" for tests (fixes: #951)

This allows running the test suite against FFmpeg builds which do not
have libx264 enabled.

tests/test_codec_context.py

@@ -204,7 +204,7 @@ def image_sequence_encode(self, codec_name):
                 self.assertEqual(frame.format.name, pix_fmt)
 
     def test_encoding_h264(self):
-        self.video_encoding("libx264", {"crf": "19"})
+        self.video_encoding("h264", {"crf": "19"})
 
     def test_encoding_mpeg4(self):
         self.video_encoding("mpeg4")
@@ -282,11 +282,7 @@ def video_encoding(self, codec_name, options={}, codec_tag=None):
                 packet_sizes.append(packet.size)
                 f.write(packet)
 
-        dec_codec_name = codec_name
-        if codec_name == "libx264":
-            dec_codec_name = "h264"
-
-        ctx = av.Codec(dec_codec_name, "r").create()
+        ctx = av.Codec(codec_name, "r").create()
         ctx.open()
 
         decoded_frame_count = 0

tests/test_encode.py

@@ -120,7 +120,7 @@ def test_encoding_with_pts(self):
         path = self.sandboxed("video_with_pts.mov")
 
         with av.open(path, "w") as output:
-            stream = output.add_stream("libx264", 24)
+            stream = output.add_stream("h264", 24)
             stream.width = WIDTH
             stream.height = HEIGHT
             stream.pix_fmt = "yuv420p"