decoder/ffmpeg: use AVCodecParameters on FFmpeg 3.1

The AVCodecContext attribute is deprecated.

NEWS

@@ -2,6 +2,7 @@ ver 0.19.18 (not yet released)
 * decoder
   - ffmpeg: fix crash with older FFmpeg versions (< 3.0)
   - ffmpeg: log detailed error message
+  - ffmpeg: support FFmpeg 3.1
 
 ver 0.19.17 (2016/07/09)
 * decoder

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -76,6 +76,24 @@ ffmpeg_init(gcc_unused const config_param &param)
 	return true;
 }
 
+#if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(57, 5, 0)
+
+gcc_pure
+static const AVCodecParameters &
+GetCodecParameters(const AVStream &stream)
+{
+	return *stream.codecpar;
+}
+
+gcc_pure
+static AVSampleFormat
+GetSampleFormat(const AVCodecParameters &codec_params)
+{
+	return AVSampleFormat(codec_params.format);
+}
+
+#else
+
 gcc_pure
 static const AVCodecContext &
 GetCodecParameters(const AVStream &stream)
@@ -90,6 +108,8 @@ GetSampleFormat(const AVCodecContext &codec_context)
 	return codec_context.sample_fmt;
 }
 
+#endif
+
 gcc_pure
 static bool
 IsAudio(const AVStream &stream)