--- a/libgsmfrp/internal.h	Sat Nov 19 09:03:57 2022 +0000
+++ b/libgsmfrp/internal.h	Sat Nov 19 20:16:09 2022 +0000
@@ -11,12 +11,19 @@
 	LOST_SID,
 };
 
-typedef unsigned char cparam;
-
 struct gsmfr_preproc_state {
 	enum rx_state	rx_state;
 	int		got_valid_sid;
 	gsm_frame	speech_frame;
-	cparam		cnoise_larc[8];
-	cparam		cnoise_xmaxc[4];
+	gsm_byte	sid_prefix[5];
+	uint8_t		sid_xmaxc[4];
+	uint32_t	cn_random_lfsr;
+	unsigned	cn_random_6fold;
 };
+
+/* we use the same LFSR PRNG for CN as ETSI EFR implementation */
+#define PN_INITIAL_SEED 0x70816958L   /* Pseudo noise generator seed value  */
+
+/* internal function */
+extern void gsmfr_preproc_gen_cn(struct gsmfr_preproc_state *state,
+				 gsm_byte *frame);