Merged in stream-id-to-mime (pull request #259)

codec/codecutil/helpers.go: added helpers.go file with SIDToMIMEType function to provide MIME type given a stream ID

Approved-by: Alan Noble <anoble@gmail.com>

codec/codecutil/helpers.go

@@ -0,0 +1,51 @@
+/*
+DESCRIPTIONS
+  helpers.go provides general codec related helper functions.
+
+AUTHORS
+  Saxon A. Nelson-Milton <saxon@ausocean.org>
+
+LICENSE
+  Copyright (C) 2019 the Australian Ocean Lab (AusOcean).
+
+  It is free software: you can redistribute it and/or modify them
+  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.
+
+  It 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
+  in gpl.txt.  If not, see http://www.gnu.org/licenses.
+*/
+
+package codecutil
+
+import "errors"
+
+// Stream types
+const (
+	H264SID  = 27
+	H265SID  = 36
+	MJPEGSID = 28
+	ADPCMSID = 192
+)
+
+// SIDToMIMEType will return the corresponding MIME type for passed stream ID.
+func SIDToMIMEType(id int) (string, error) {
+	switch id {
+	case H264SID:
+		return "video/h264", nil
+	case H265SID:
+		return "video/h265", nil
+	case MJPEGSID:
+		return "video/x-motion-jpeg", nil
+	case ADPCMSID:
+		return "audio/adpcm", nil
+	default:
+		return "", errors.New("unkown stream ID")
+	}
+}