diff --git a/include/Makefile.am b/include/Makefile.am
index b16ce5c..ddb25df 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1 +1,5 @@
 SUBDIRS = gapk
+
+if ENABLE_GSMHR
+SUBDIRS += gsmhr
+endif
diff --git a/include/gsmhr/Makefile.am b/include/gsmhr/Makefile.am
new file mode 100644
index 0000000..368a2b8
--- /dev/null
+++ b/include/gsmhr/Makefile.am
@@ -0,0 +1 @@
+noinst_HEADERS =	gsmhr.h
diff --git a/include/gsmhr/gsmhr.h b/include/gsmhr/gsmhr.h
new file mode 100644
index 0000000..17d42cb
--- /dev/null
+++ b/include/gsmhr/gsmhr.h
@@ -0,0 +1,40 @@
+/* HR (GSM 06.20) codec */
+
+/*
+ * This file is part of gapk (GSM Audio Pocket Knife).
+ *
+ * gapk 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.
+ *
+ * gapk 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 gapk.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __GSM_HR_H__
+#define __GSM_HR_H__
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct gsmhr;
+
+struct gsmhr *gsmhr_init(void);
+void          gsmhr_exit(struct gsmhr *state);
+int           gsmhr_encode(struct gsmhr *state, int16_t *hr_params, const int16_t *pcm);
+int           gsmhr_decode(struct gsmhr *state, int16_t *pcm, const int16_t *hr_params);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __GSM_HR_H__ */