audio: From RTP point of view we can use one payload for HR/FR AMR

Remove the separation of half-rate and full-rate AMR. The used rate
can be found inside the AMR payload. The signalling of what kind of
traffic channel is used can be done with the GSM 08.08 Chosen
Channel IE in the Assignment Complete message.

This way I can use a fixed payload type in the MGCP GateWay but
have a mixed TCH/F and TCH/H config. E.g. use TCH/F FR3 for some
subscribers when connected to MSC A but use AMR5.9 on a TCH/F for
MSC B when all TCH/Hs are gone.

openbsc/include/openbsc/rtp_proxy.h

@@ -32,8 +32,7 @@
 #define RTP_PT_GSM_FULL 3
 #define RTP_PT_GSM_HALF 96
 #define RTP_PT_GSM_EFR 97
-#define RTP_PT_AMR_FULL 98
-#define RTP_PT_AMR_HALF 99
+#define RTP_PT_AMR 98
 
 enum rtp_rx_action {
 	RTP_NONE,

openbsc/src/libbsc/abis_rsl.c

@@ -1543,9 +1543,8 @@ static uint8_t ipa_rtp_pt_for_lchan(struct gsm_lchan *lchan)
 	case GSM48_CMODE_SPEECH_AMR:
 		switch (lchan->type) {
 		case GSM_LCHAN_TCH_F:
-			return RTP_PT_AMR_FULL;
 		case GSM_LCHAN_TCH_H:
-			return RTP_PT_AMR_HALF;
+			return RTP_PT_AMR;
 		default:
 			break;
 		}