-------- Original Message --------
Subject: Re: [Live-devel] Delay problem of the first RTCP "SR" packet
From: Steve Ha <[email protected]>
To: LIVE555 Streaming Media - development & use <[email protected]>
Date: 2021-01-22 04:52+0300
Thanks for your quick and useful response,
I have checked it and admit that the "SR" always comes to the client before the
first RTP packet.
But I still wonder about two things:
1) Since the RTPTimestamp bound to the first "SR" is different from the one
bound to the first RTP packet, how can PTS be synchronized to the server's NTP correctly
at the client side?
Steve,
This might get mangled (ASCII art formatting) but
From RFC 3550, 6.5.1
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
sender | NTP timestamp, most significant word |
info +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NTP timestamp, least significant word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTP timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The NTP time stamp in the sender report is accompanied by the random offset NTP
stream timestamp also used RTP packet headers, so the receiver should be able
to carry forward the offset between sender NTP time and RTP packets.
2) Does PTS at client always monotonically increase even in case RTPTimestamp
(32-bit) is wrapped around?.
that I don't know....
Regards.
Steve.
On Fri, Jan 22, 2021 at 4:01 PM Ross Finlayson <[email protected]
<mailto:[email protected]>> wrote:
> On Jan 22, 2021, at 4:05 PM, Steve Ha <[email protected]
<mailto:[email protected]>> wrote:
>
> My question is how can I force the first RTCP "SR" packet to be delivered
at the same time as the first RTP packet so that the RTSP client could get all frames with
correct PTS?
Basically, you can’t. (But even if you could, there’d be no guarantee that
it would be received, as it (like all RTCP (and RTP packets) are datagrams.)
However, our RTSP server implementation *does* send an initial RTCP “SR”,
before the first RTP packet, precisely for this reason. (See
“OnDemandServerMediaSubsession.cpp”, line 550.)
Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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