export: use codec IDs rather than strings

Vastly improves portability between library versions.

app/codec/exportcodec.h

@@ -0,0 +1,58 @@
+/***
+
+  Olive - Non-Linear Video Editor
+  Copyright (C) 2019 Olive Team
+
+  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 3 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, see <http://www.gnu.org/licenses/>.
+
+***/
+
+#ifndef EXPORTCODEC_H
+#define EXPORTCODEC_H
+
+#include <QObject>
+#include <QString>
+
+#include "common/define.h"
+
+OLIVE_NAMESPACE_ENTER
+
+class ExportCodec : public QObject {
+public:
+  enum Codec {
+    kCodecDNxHD,
+    kCodecH264,
+    kCodecH265,
+    kCodecOpenEXR,
+    kCodecPNG,
+    kCodecProRes,
+    kCodecTIFF,
+
+    kCodecMP2,
+    kCodecMP3,
+    kCodecAAC,
+    kCodecPCM,
+
+    kCodecCount
+  };
+
+  static QString GetCodecName(Codec c);
+
+  static bool IsCodecAStillImage(Codec c);
+
+};
+
+OLIVE_NAMESPACE_EXIT
+
+#endif // EXPORTCODEC_H