Expose the current sequence number via an AVOption - this can
be used both for setting the initial sequence number, or for
querying the current number.
---
libavformat/rtpenc.c | 10 +++++++++-
libavformat/rtpenc.h | 2 +-
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/libavformat/rtpenc.c b/libavformat/rtpenc.c
index 0f5307d..d0140ee 100644
--- a/libavformat/rtpenc.c
+++ b/libavformat/rtpenc.c
@@ -35,6 +35,7 @@ static const AVOption options[] = {
{ "payload_type", "Specify RTP payload type", offsetof(RTPMuxContext,
payload_type), AV_OPT_TYPE_INT, {.i64 = -1 }, -1, 127,
AV_OPT_FLAG_ENCODING_PARAM },
{ "ssrc", "Stream identifier", offsetof(RTPMuxContext, ssrc),
AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
{ "cname", "CNAME to include in RTCP SR packets", offsetof(RTPMuxContext,
cname), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, AV_OPT_FLAG_ENCODING_PARAM },
+ { "seq", "Starting sequence number", offsetof(RTPMuxContext, seq),
AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, AV_OPT_FLAG_ENCODING_PARAM },
{ NULL },
};
@@ -124,6 +125,13 @@ static int rtp_write_header(AVFormatContext *s1)
/* Round the NTP time to whole milliseconds. */
s->first_rtcp_ntp_time = (s1->start_time_realtime / 1000) * 1000 +
NTP_OFFSET_US;
+ // Pick a random sequence start number, but in the lower end of the
+ // available range, so that any wraparound doesn't happen immediately.
+ // (Immediate wraparound would be an issue for SRTP.)
+ if (s->seq < 0)
+ s->seq = av_get_random_seed() & 0x0fff;
+ else
+ s->seq &= 0xffff; // Use the given parameter, wrapped to the right
interval
if (s1->packet_size) {
if (s1->pb->max_packet_size)
@@ -309,7 +317,7 @@ void ff_rtp_send_data(AVFormatContext *s1, const uint8_t
*buf1, int len, int m)
avio_write(s1->pb, buf1, len);
avio_flush(s1->pb);
- s->seq++;
+ s->seq = (s->seq + 1) & 0xffff;
s->octet_count += len;
s->packet_count++;
}
diff --git a/libavformat/rtpenc.h b/libavformat/rtpenc.h
index f797348..d19b0fd 100644
--- a/libavformat/rtpenc.h
+++ b/libavformat/rtpenc.h
@@ -31,7 +31,7 @@ struct RTPMuxContext {
int payload_type;
uint32_t ssrc;
const char *cname;
- uint16_t seq;
+ int seq;
uint32_t timestamp;
uint32_t base_timestamp;
uint32_t cur_timestamp;
--
1.7.9.4
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