--- a/test-voice/rtp_tx.c	Sat May 11 22:10:38 2024 -0800
+++ b/test-voice/rtp_tx.c	Sat May 11 22:27:07 2024 -0800
@@ -119,6 +119,7 @@
 	else {
 		free(play_buffer);
 		play_buffer = 0;
+		printf("file play finished\n");
 	}
 }
 
@@ -236,6 +237,53 @@
 }
 
 void
+play_file_offset(filename, offset)
+	char *filename;
+	unsigned offset;
+{
+	int fd;
+	struct stat st;
+	unsigned pre_offset;
+
+	if (play_buffer) {
+		fprintf(stderr, "error: file play already in progress\n");
+		return;
+	}
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
+		perror(filename);
+		return;
+	}
+	fstat(fd, &st);
+	if (!S_ISREG(st.st_mode)) {
+		close(fd);
+		fprintf(stderr, "error: %s is not a regular file\n", filename);
+		return;
+	}
+	if (st.st_size % 160) {
+		close(fd);
+		fprintf(stderr,
+			"error: size of %s is not a multiple of 160 bytes\n",
+			filename);
+		return;
+	}
+	play_buffer = malloc(st.st_size + 160);
+	if (!play_buffer) {
+		close(fd);
+		fprintf(stderr, "unable to malloc buffer for %s\n", filename);
+		return;
+	}
+	pre_offset = 160 - offset;
+	memset(play_buffer, pcm_fill_octet, pre_offset);
+	read(fd, play_buffer + pre_offset, st.st_size);
+	close(fd);
+	memset(play_buffer + pre_offset + st.st_size, pcm_fill_octet, offset);
+	play_buf_nframes = st.st_size / 160 + 1;
+	play_buf_ptr = 0;
+	play_loop = 0;
+}
+
+void
 play_file_stop()
 {
 	if (!play_buffer)