--- a/amrefr/Makefile	Wed May 08 23:43:26 2024 +0000
+++ b/amrefr/Makefile	Thu May 09 00:12:33 2024 +0000
@@ -1,6 +1,6 @@
 CC=	gcc
 CFLAGS=	-O2
-PROGS=	amrefr-encode-r amrefr-tseq-dec amrefr-tseq-enc
+PROGS=	amrefr-decode-r amrefr-encode-r amrefr-tseq-dec amrefr-tseq-enc
 LIBEFR=	../libgsmefr/libgsmefr.a
 LIBAMR=	../libtwamr/libtwamr.a
 LIBTEST=../libtest/libtest.a
@@ -10,6 +10,9 @@
 
 all:	${PROGS}
 
+amrefr-decode-r:	decode-r.o ${LIBST}
+	${CC} ${CFLAGS} -o $@ $^
+
 amrefr-encode-r:	encode-r.o ${LIBST}
 	${CC} ${CFLAGS} -o $@ $^
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/amrefr/decode-r.c	Thu May 09 00:12:33 2024 +0000
@@ -0,0 +1,75 @@
+/*
+ * amrefr-decode-r is a counterpart to gsmefr-decode-r, implementing
+ * "alternative EFR" by way of libtwamr.  Unlike standard gsmefr-decode-r,
+ * this version cannot handle SID frames in input: they are not explicitly
+ * checked for, but an input containing SIDs will not be decoded correctly.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "../libgsmefr/gsm_efr.h"
+#include "../libtwamr/tw_amr.h"
+#include "../libtest/binreader.h"
+#include "../libtest/robewrite.h"
+
+main(argc, argv)
+	char **argv;
+{
+	FILE *binf, *outf;
+	struct amr_decoder_state *state;
+	uint8_t frame[BINFILE_MAX_FRAME];
+	struct amr_param_frame amr_frame;
+	int16_t pcm[160];
+	int rc, bfi;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: %s input.gsmx output.robe\n", argv[0]);
+		exit(1);
+	}
+	binf = fopen(argv[1], "r");
+	if (!binf) {
+		perror(argv[1]);
+		exit(1);
+	}
+	outf = fopen(argv[2], "w");
+	if (!outf) {
+		perror(argv[2]);
+		exit(1);
+	}
+	state = amr_decoder_create();
+	if (!state) {
+		perror("amr_decoder_create()");
+		exit(1);
+	}
+	amr_frame.mode = 0x87;
+	for (;;) {
+		rc = binfile_read_frame(binf, frame);
+		if (rc < 0) {
+			fprintf(stderr, "error: garbage in %s\n", argv[1]);
+			exit(1);
+		}
+		if (!rc)
+			break;
+		if (frame[0] == 0xBF)
+			bfi = 1;
+		else if ((frame[0] & 0xF0) == 0xC0)
+			bfi = 0;
+		else {
+			fprintf(stderr,
+				"error: %s is not in EFR codec format\n",
+				argv[1]);
+			exit(1);
+		}
+		if (bfi)
+			amr_frame.type = RX_NO_DATA;
+		else {
+			amr_frame.type = RX_SPEECH_GOOD;
+			EFR_frame2params(frame, amr_frame.param);
+		}
+		amr_decode_frame(state, &amr_frame, pcm);
+		write_pcm_to_robe(outf, pcm);
+	}
+	fclose(outf);
+	exit(0);
+}