Re: [Live-devel] How framerate is passing to rtsp client

Paweł Domagalski Fri, 01 Apr 2016 05:09:31 -0700

I have compared logs from my rtsp server ( runned on embedded device)and rtsp client ( runned on PC) and I found difference in timestamps.

On the server has elapsed 4.7 s
On the testRTSPClient has elapsed 1.6 s.

First timestamps are similar but next one is +110 ms on the server and +40 ms on the client.

I have dumped RTP transmission using wireshark and I have checked thattimestamp field is incremented by 3600 with every frame;I have read document RFC6184 chapter 5. RTP payload format. There isdescription of timestamp:"Timestamp: 32 bits The RTP timestamp is set to the sampling timestampof the content. A 90 kHz clock rate MUST be used."

I am working on embedded device and I assume that my system timer is not90kHz clocked. Am I right ? I must investigate how timestamp iscalculated. Any advice ? RTPSink class will be good place to investigate ?

What else, I see that first packet is not displayed by testRTSPClientbut it is another issue which probably has not influence on my problem.


Below I pasted logs from my server and from testRTSPClient application.

Regards

Server:
PIPE:LOS: Sending 13164 bytes   Presentation time: 567993726.600011
PIPE:LOS: Sending 10742 bytes   Presentation time: 567993726.719010
PIPE:LOS: Sending 11823 bytes   Presentation time: 567993726.827011
PIPE:LOS: Sending 11831 bytes   Presentation time: 567993726.946010
PIPE:LOS: Sending 11840 bytes   Presentation time: 567993727.053011
PIPE:LOS: Sending 12131 bytes   Presentation time: 567993727.173045
PIPE:LOS: Sending 11929 bytes   Presentation time: 567993727.281011
PIPE:LOS: Sending 11992 bytes   Presentation time: 567993727.399010
PIPE:LOS: Sending 11987 bytes   Presentation time: 567993727.508013
PIPE:LOS: Sending 15912 bytes   Presentation time: 567993727.625010
PIPE:LOS: Sending 11970 bytes   Presentation time: 567993727.744019
PIPE:LOS: Sending 11889 bytes   Presentation time: 567993727.854011
PIPE:LOS: Sending 11817 bytes   Presentation time: 567993727.965011

PIPE:LOS: Sending 4137 bytes with truncated 7685 bytes Presentationtime: 567993728.084010

PIPE:LOS: Sending 7685 bytes    Presentation time: 567993728.094322
PIPE:LOS: Sending 11821 bytes   Presentation time: 567993728.193010
PIPE:LOS: Sending 11857 bytes   Presentation time: 567993728.311010
PIPE:LOS: Sending 11833 bytes   Presentation time: 567993728.421011
PIPE:LOS: Sending 11788 bytes   Presentation time: 567993728.541010
PIPE:LOS: Sending 15631 bytes   Presentation time: 567993728.650010
PIPE:LOS: Sending 11713 bytes   Presentation time: 567993728.768010
PIPE:LOS: Sending 11683 bytes   Presentation time: 567993728.877011
PIPE:LOS: Sending 11784 bytes   Presentation time: 567993728.996011
PIPE:LOS: Sending 11707 bytes   Presentation time: 567993729.104011
PIPE:LOS: Sending 11759 bytes   Presentation time: 567993729.224049
PIPE:LOS: Sending 11814 bytes   Presentation time: 567993729.334011

PIPE:LOS: Sending 8925 bytes with truncated 2975 bytes Presentationtime: 567993729.447011

PIPE:LOS: Sending 2975 bytes    Presentation time: 567993729.459502
PIPE:LOS: Sending 11726 bytes   Presentation time: 567993729.560011
PIPE:LOS: Sending 15451 bytes   Presentation time: 567993729.679049
PIPE:LOS: Sending 11609 bytes   Presentation time: 567993729.788010
PIPE:LOS: Sending 11605 bytes   Presentation time: 567993729.907035
PIPE:LOS: Sending 11724 bytes   Presentation time: 567993730.016011
PIPE:LOS: Sending 11697 bytes   Presentation time: 567993730.134052
PIPE:LOS: Sending 11729 bytes   Presentation time: 567993730.243012
PIPE:LOS: Sending 11911 bytes   Presentation time: 567993730.361011
PIPE:LOS: Sending 12043 bytes   Presentation time: 567993730.471021
PIPE:LOS: Sending 12031 bytes   Presentation time: 567993730.590034
PIPE:LOS: Sending 15888 bytes   Presentation time: 567993730.698011

PIPE:LOS: Sending 9609 bytes with truncated 2372 bytes Presentationtime: 567993730.818010

PIPE:LOS: Sending 2372 bytes    Presentation time: 567993730.833537
PIPE:LOS: Sending 11981 bytes   Presentation time: 567993730.928011
PIPE:LOS: Sending 12015 bytes   Presentation time: 567993731.046010
PIPE:LOS: Sending 12124 bytes   Presentation time: 567993731.157018
PIPE:LOS: Sending 12024 bytes   Presentation time: 567993731.275042
PIPE:LOS: Sending 12051 bytes   Presentation time: 567993731.383011


testRTSPClient:

Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received10738 bytes. Presentation time: 567993726.682812Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11819 bytes. Presentation time: 567993726.722812Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11827 bytes. Presentation time: 567993726.762812Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11836 bytes. Presentation time: 567993726.802800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12127 bytes. Presentation time: 567993726.842800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11925 bytes. Presentation time: 567993726.882800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11988 bytes. Presentation time: 567993726.922800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11983 bytes. Presentation time: 567993726.962800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received15908 bytes. Presentation time: 567993727.002800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11966 bytes. Presentation time: 567993727.042800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11885 bytes. Presentation time: 567993727.082800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11813 bytes. Presentation time: 567993727.122800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11818 bytes. Presentation time: 567993727.162800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11817 bytes. Presentation time: 567993727.202800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11853 bytes. Presentation time: 567993727.242800Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11829 bytes. Presentation time: 567993727.282788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11784 bytes. Presentation time: 567993727.322788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received15627 bytes. Presentation time: 567993727.362788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11709 bytes. Presentation time: 567993727.402788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11679 bytes. Presentation time: 567993727.442788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11780 bytes. Presentation time: 567993727.482788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11703 bytes. Presentation time: 567993727.522788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11755 bytes. Presentation time: 567993727.562788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11810 bytes. Presentation time: 567993727.602788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11896 bytes. Presentation time: 567993727.642788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11722 bytes. Presentation time: 567993727.682788Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received15447 bytes. Presentation time: 567993727.722776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11605 bytes. Presentation time: 567993727.762776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11601 bytes. Presentation time: 567993727.802776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11720 bytes. Presentation time: 567993727.842776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11693 bytes. Presentation time: 567993727.882776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11725 bytes. Presentation time: 567993727.922776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11907 bytes. Presentation time: 567993727.962776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12039 bytes. Presentation time: 567993728.002776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12027 bytes. Presentation time: 567993728.042776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received15884 bytes. Presentation time: 567993728.082776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11977 bytes. Presentation time: 567993728.122776Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received11977 bytes. Presentation time: 567993728.162764Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12011 bytes. Presentation time: 567993728.202764Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12120 bytes. Presentation time: 567993728.242764Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12020 bytes. Presentation time: 567993728.282764Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received12047 bytes. Presentation time: 567993728.322764




On 31/03/16 22:33, Ross Finlayson wrote:

The (64-bit) "presentation time” values are not passed directly from the server 
to the client; instead, they are transferred implicitly, using the (32-bit) RTP 
timestamps in each RTP packet, plus periodic RTCP packets that provide the mapping 
from RTP timestamp to “presentation time”.  This is all very complicated, and is 
(IMHO) a flaw in the RTP/RTCP design; it was done to save space in each RTP packet.  
However, our code (at both the server end and the client end) handles this all 
automatically, so that you don’t need to worry about it.

HOWEVER, for this to work properly (when writing a server that uses the LIVE555 
code), the "presentation time” values that the server generates MUST be aligned 
with ‘wall clock’ time - i.e., the times that you’d get by calling “gettimeofday()”.

Therefore, you should go back to using “gettimeofday()” to generate your 
presentation times (in your server code).  (However, if you have more than one 
NAL unit for the same video frame, then each of these NAL units should be given 
the same presentation time.)


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/


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Paweł Domagalski
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Mobica Ltd.
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Re: [Live-devel] How framerate is passing to rtsp client

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