<div dir="ltr">thank you. Ross! I found the reason it this answer<div><br></div><div><p style="color:rgb(72,72,72);font-family:verdana,sans-serif;font-size:12px">"But I notice that there's an abrupt change in a stream's presentation times after the first RTCP "SR" packet has been received. Is this a bug?</p><p style="color:rgb(72,72,72);font-family:verdana,sans-serif;font-size:12px">No, this is normal, and expected; there's no bug here. This happens because the first few presentation times - before RTCP synchronization occurs - are just 'guesses' made by the receiving code (based on the receiver's 'wall clock' and the RTP timestamp). However, once RTCP synchronization occurs, all subsequent presentation times will be accurate.<br>This means is that a receiver should be prepared for the fact that the first few presentation times (until RTCP synchronization starts) will not be accurate. The code, however, can check this by calling "RTPSource:: hasBeenSynchronizedUsingRTCP()". If this returns False, then the presentation times are not accurate, and should not be used for synchronization. However, once the call to returns True, then the presentation times (from then on) will be accurate. "</p></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div style="font-size:12.8px"><br></div><div style="font-size:12.8px"><table border="0" cellpadding="0" cellspacing="0" width="450" style="border-spacing:0px;color:rgb(0,0,0);font-family:Lato,Arial,San-serif;font-size:14px;line-height:20px;table-layout:fixed;background-color:transparent"><tbody><tr><td align="left" valign="top" width="170" style="padding:0px"><p style="margin:0px 10px 10px 0px;font-family:Helvetica,Arial,sans-serif;font-size:10px;line-height:12px"><a href="http://www.avtodoria.ru/" style="color:rgb(17,85,204)" target="_blank"><img src="https://docs.google.com/uc?export=download&id=0B4M0RoVeGV5haVBOMHZyUkJzcWs&revid=0B4M0RoVeGV5hU0p6S2YvcGRYYjkva2ZlYm13ZTVKMGtkaHFvPQ" alt=" ООО "Автодория"" width="96" height="19"></a><br></p><p style="margin:0px 0px 10px;font-size:0px;line-height:0;font-family:Helvetica,Arial,sans-serif"></p></td><td align="left" valign="top" nowrap width="16" style="padding:0px;border-left-width:6px;border-left-style:solid;border-left-color:rgb(78,188,80)"><img src="https://s3.amazonaws.com/htmlsig-assets/spacer.gif" width="10" style="border:0px;vertical-align:middle"></td><td align="left" valign="top" nowrap width="274" style="padding:0px"><p style="margin:0px 0px 10px;font-family:Helvetica,Arial,sans-serif;font-size:10px;line-height:12px"><font color="#2d2b2b"><b>Артур Хайруллин</b></font><span style="color:rgb(33,33,33)"> / </span><font color="#2d2b2b">Системный программист</font><br><a href="mailto:ah@avtodoria.ru" style="color:rgb(78,188,80);text-decoration:none;display:inline;background-color:transparent" target="_blank">ah@avtodoria.ru</a><span style="color:rgb(33,33,33)"> / +</span><font color="#2d2b2b">7 904 677 74 46</font><br></p><p style="margin:0px 0px 10px;font-family:Helvetica,Arial,sans-serif;font-size:10px;line-height:12px"><span style="font-weight:bold;color:rgb(45,43,43)">ООО "Автодория"</span> <br><span style="color:rgb(45,43,43)">+7 843 524 74 12</span> <br><span style="color:rgb(45,43,43)">Казань, Технопарк в сфере высоких технологий "ИТ-парк", Петербургская, 52, офис 303</span> <br><a href="http://www.avtodoria.ru/" style="color:rgb(78,188,80);text-decoration:none;display:inline;background-color:transparent" target="_blank">www.avtodoria.ru</a></p><p style="margin:0px 0px 10px;font-family:Helvetica,Arial,sans-serif;font-size:10px;line-height:12px"><b>Инновации спасают жизни!</b></p></td></tr></tbody></table></div><div style="font-size:12.8px"><br></div></div></div></div></div></div>
<br><div class="gmail_quote">2016-10-29 18:02 GMT+03:00 Ross Finlayson <span dir="ltr"><<a href="mailto:finlayson@live555.com" target="_blank">finlayson@live555.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I’m sorry, but I’m not sure that I understand your question. However, please note that LIVE555 programmers should never have to deal with RTP timestamps directly. Our software automatically uses RTCP to convert presentation times to RTP timestamps (when transmitting) and back to presentation times (when receiving). Presentation times are all that you need to think about. (Therefore, please don’t mention the word “timestamp” again; this will lead to unnecessary confusion.)<br>
<br>
Also, if you haven’t done so already, please read our FAQ; especially these entries:<br>
<a href="http://live555.com/liveMedia/faq.html#separate-rtp-streams" rel="noreferrer" target="_blank">http://live555.com/liveMedia/<wbr>faq.html#separate-rtp-streams</a><br>
<a href="http://live555.com/liveMedia/faq.html#rtcp-synchronization-issue" rel="noreferrer" target="_blank">http://live555.com/liveMedia/<wbr>faq.html#rtcp-synchronization-<wbr>issue</a><br>
<br>
Finally, if you are receiving a RTSP/RTP/RTCP stream (i.e., if you are a RTSP client), then it’s perfectly OK for the presentation time of the received frames (after RTCP synchronization) to be different from ‘wall clock’ time. This can happen if the sender (i.e., RTSP server) has a clock that is not set to ‘wall clock’ time. But that’s OK; it’s only the *difference* between successive presentation times that matters (for proper playback, and audio/video synchronization).<br>
<br>
(If, however, you are writing a RTSP *server* that uses our code, then the presentation times that it sends (for each of its frames) should be aligned with the server computer’s ‘wall clock’ time (i.e., the time that you’d get by calling “gettimeofday()”.)<br>
<br>
Ross Finlayson<br>
Live Networks, Inc.<br>
<a href="http://www.live555.com/" rel="noreferrer" target="_blank">http://www.live555.com/</a><br>
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</blockquote></div><br></div>