decoder/ffmpeg: add AVFrame wrapper class

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -27,6 +27,7 @@
 #include "lib/ffmpeg/LogError.hxx"
 #include "lib/ffmpeg/Init.hxx"
 #include "lib/ffmpeg/Buffer.hxx"
+#include "lib/ffmpeg/Frame.hxx"
 #include "../DecoderAPI.hxx"
 #include "FfmpegMetaData.hxx"
 #include "FfmpegIo.hxx"
@@ -574,15 +575,7 @@ FfmpegDecode(DecoderClient &client, InputStream &input,
 
 	FfmpegParseMetaData(client, format_context, audio_stream);
 
-	AVFrame *frame = av_frame_alloc();
-	if (!frame) {
-		LogError(ffmpeg_domain, "Could not allocate frame");
-		return;
-	}
-
-	AtScopeExit(&frame) {
-		av_frame_free(&frame);
-	};
+	Ffmpeg::Frame frame;
 
 	FfmpegBuffer interleaved_buffer;
 

src/lib/ffmpeg/Frame.hxx

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2003-2019 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_FFMPEG_FRAME_HXX
+#define MPD_FFMPEG_FRAME_HXX
+
+extern "C" {
+#include <libavutil/frame.h>
+}
+
+#include <new>
+
+namespace Ffmpeg {
+
+class Frame {
+	AVFrame *frame;
+
+public:
+	Frame():frame(av_frame_alloc()) {
+		if (frame == nullptr)
+			throw std::bad_alloc();
+	}
+
+	~Frame() noexcept {
+		av_frame_free(&frame);
+	}
+
+	Frame(const Frame &) = delete;
+	Frame &operator=(const Frame &) = delete;
+
+	AVFrame &operator*() noexcept {
+		return *frame;
+	}
+};
+
+} // namespace Ffmpeg
+
+#endif