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<p>Steve,</p>
<p><br>
</p>
<p>Thanks for the answer. Unfortunately, I don't entirely
understand either. Basically I was having trouble with FFMPEG,
but I tested with VLC and it did sync. I will try rebuilding
ffmpeg and resyncing and I set up a local NTP server to improve
device NTP synchronization, I'm not sure why that would matter as
I had multiple streams from the same camera failing to sync - and
they share the same device clock. So maybe ffmpeg isn't the
answer.</p>
<p>I chased down RFC6051 as I thought if it were fairly easy to turn
on, it is likely many media sinks would understand it and Do The
Right Thing.</p>
<p>Unfortunately, this can be muddy waters because ONVIF chose a
slightly different method of achieving the same goal and while
similar the header extension is not identical. Optimally, there
would be easily enabled code to generate the necessary header
extensions for RFC 6051 compliant headers (A or B), ONVIF
compliant NTP headers, both, or neither.</p>
<p>If implementing RFC 6051 header decode (assuming it were
available) is problematic - it might be easier to look at sending
rapid resynchronization request packets - RFC 6051 3.2:</p>
<pre class="newpage"> If the RTP/AVPF profile [<a href="https://tools.ietf.org/html/rfc4585" title=""Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)"">RFC4585</a>] is in use, this feedback message
MAY be sent by a receiver to indicate that it's unable to synchronise
some media streams, and desires that the media source transmit an
RTCP SR packet as soon as possible</pre>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">-David</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">-------- Original Message --------<br>
Subject: Re: [Live-devel] Delay problem of the first RTCP "SR"
packet<br>
From: Steve Ha <a class="moz-txt-link-rfc2396E" href="mailto:steveha@u2sr.com"><steveha@u2sr.com></a><br>
To: LIVE555 Streaming Media - development & use
<a class="moz-txt-link-rfc2396E" href="mailto:live-devel@us.live555.com"><live-devel@us.live555.com></a><br>
Date: 2021-01-22 05:09+0300<br>
</div>
<blockquote type="cite"
cite="mid:CAOckaMe7tPYE+TtRwEhHOA159TF63q5vozFDKUaip+zdtuB=LA@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Hi David,
<div>The RFC-6051 seems good for quickly synchronization, but it
requires a big effort to adapt to the current library and I am
not sure if it is worth enough to do so.</div>
<div>I don't understand your issue well so I have no idea.
Sorry.</div>
<div><br>
</div>
<div>Steve.</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Jan 22, 2021 at 8:44
PM David Gessel <<a href="mailto:gessel@blackrosetech.com"
moz-do-not-send="true">gessel@blackrosetech.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Steve,<br>
<br>
I am having some issues with sync due to either late or
ignored SR packet timestamps. Ross provided a really good
answer to my question - to which I owe a response and am
working toward (side-quests have intervened as a kernel update
once again broke my e1000e network driver and this time the
fixes are not fixin' the problem - totally irrelevant to
this).<br>
<br>
In any event there is a standard defined to extend the RTP
packet structure to include NTP time stamps, RFC 6051,
precisely to enable more rapid synchronization of multi-source
RTSP streams. I feel Live555 would benefit from at least
having the capability of optionally adding RFC6051 NTP header
extensions.<br>
<br>
-David<br>
<br>
<br>
<br>
-------- Original Message --------<br>
Subject: Re: [Live-devel] Delay problem of the first RTCP "SR"
packet<br>
From: Ross Finlayson <<a
href="mailto:finlayson@live555.com" target="_blank"
moz-do-not-send="true">finlayson@live555.com</a>><br>
To: LIVE555 Streaming Media - development & use <<a
href="mailto:live-devel@us.live555.com" target="_blank"
moz-do-not-send="true">live-devel@us.live555.com</a>><br>
Date: 2021-01-22 10:01+0300<br>
<br>
> <br>
> <br>
>> On Jan 22, 2021, at 4:05 PM, Steve Ha <<a
href="mailto:steveha@u2sr.com" target="_blank"
moz-do-not-send="true">steveha@u2sr.com</a>> wrote:<br>
>><br>
>> 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?<br>
> <br>
> 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.)<br>
> <br>
> 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.)<br>
> <br>
> <br>
> Ross Finlayson<br>
> Live Networks, Inc.<br>
> <a href="http://www.live555.com/" rel="noreferrer"
target="_blank" moz-do-not-send="true">http://www.live555.com/</a><br>
> <br>
> <br>
> _______________________________________________<br>
> live-devel mailing list<br>
> <a href="mailto:live-devel@lists.live555.com"
target="_blank" moz-do-not-send="true">live-devel@lists.live555.com</a><br>
> <a
href="http://lists.live555.com/mailman/listinfo/live-devel"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://lists.live555.com/mailman/listinfo/live-devel</a><br>
> <br>
_______________________________________________<br>
live-devel mailing list<br>
<a href="mailto:live-devel@lists.live555.com" target="_blank"
moz-do-not-send="true">live-devel@lists.live555.com</a><br>
<a href="http://lists.live555.com/mailman/listinfo/live-devel"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://lists.live555.com/mailman/listinfo/live-devel</a><br>
</blockquote>
</div>
<br>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
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</blockquote>
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