rtp: fix wrong time arithmetics in osmo_rtp_build

rtp.c:154:26: warning: The left operand to '/' is always 0
        frame_diff = (usec_diff / 20000);
                      ~~~~~~~~~ ^
rtp.c:157:43: warning: The left operand to '-' is always 0
                long int frame_diff_excess = frame_diff - 1;
                                             ~~~~~~~~~~ ^
rtp.c:153:39: warning: The right operand to '+' is always 0
        usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec;
                                             ^ ~~~~~~~~~~~~~~~
rtp.c:153:29: warning: The left operand to '*' is always 0
        usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec;
                    ~~~~~~~~~~~~~~ ^
4 warnings generated.

Reported by Holger Hans Peter Freyther.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/rtp.c b/src/rtp.c
index 6245194..2a6ba54 100644
--- a/src/rtp.c
+++ b/src/rtp.c
@@ -143,11 +143,11 @@ osmo_rtp_build(struct osmo_rtp_handle *h, uint8_t payload_type,
 {
 	struct msgb *msg;
 	struct rtp_hdr *rtph;
-	struct timeval tv, tv_diff = {};
+	struct timeval tv, tv_diff;
 	long int usec_diff, frame_diff;
 
 	gettimeofday(&tv, NULL);
-	timersub(&tv_diff, &h->tx.last_tv, &tv);
+	timersub(&tv, &h->tx.last_tv, &tv_diff);
 	h->tx.last_tv = tv;
 
 	usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec;