trying to analyze RTP

[Chuck Crisler]

WOW! Thank you! :-)

On Thu, Mar 14, 2013 at 10:59 AM, Olivier Crête <olivier.crete at collabora.com
> wrote:

> Hi,
>
> You should instead feed the pcap file to GStreamer directly using
> pcapparse, you can tell pcapparse which src/dest ip/port tuple to use.
> Then you get the packets properly timestamped and delimited.
>
> Olivier
>
> On Thu, 2013-03-14 at 07:55 +0000, Thomas Greenwood wrote:
> > I think your issue may relate to packetizing of the rtp.  In udp each
> > packet is delineated by the udp packet, but when put into a file the
> > information of where each packet ends isn't available. So I guess the
> > file source will just read  chunks that don't match a single whole rtp
> > packet.  It's the same issue with sending rtp over tcp - take a look
> > at what it says in the spec http://www.ietf.org/rfc/rfc3551.txt
> >
> > Btw I haven't looked at your file so I am making some presumptions.
> >
> > -----Original Message-----
> >
> > From: Chuck Crisler
> > Sent: 13 Mar 2013 19:06:55 GMT
> > To: Discussion of the development of and with GStreamer
> > Subject: trying to analyze RTP
> >
> >
> > I am trying to establish tools to analyze RTP streams. I have a
> > wireshark packet capture that has RTP video that successfully
> > displayed. In wireshark I decoded the specific UDP as RTP, then set
> > the default H264 RTP payload type properly to analyze the packets has
> > H264. I then selected 'follow conversation' to only select that
> > particular stream. I verified that the resulting wireshark display
> > only contained the entire RTP payload from all of the selected
> > packets, the UDP headers had been removed. To do that I simply
> > compared the isolated stream display to the standard wireshark display
> > for the selected packet and matched where the initial bytes lined up.
> > I then saved that isolated stream to a file that I gave the 'rtp'
> > extension to. I then used a gstreamer based script to read the file,
> > rtp depay, h264 decode and display the stream. But the depay operation
> > failed. Here is my pipeline to process the file:
> >
> > gst-launch -v filesrc location=$1 !
> >
> 'application/x-rtp,media=video,payload=104,clock-rate=90000,encoding-name=H264'
> \
> >          ! queue ! rtph264depay ! ffdec_h264 ! ffmpegcolorspace !
> > xvimagesink
> >
> > Here are the initial log messages from the script. I had debugging for
> > rtph264depay:5
> >
> > /GstPipeline:pipeline0/GstQueue:queue0.GstPad:src: caps =
> > application/x-rtp, media=(string)video, payload=(int)104, clock-rat
> > e=(int)90000, encoding-name=(string)H264
> > /GstPipeline:pipeline0/GstRtpH264Depay:rtph264depay0.GstPad:src: caps
> > = video/x-h264
> > /GstPipeline:pipeline0/GstRtpH264Depay:rtph264depay0.GstPad:sink: caps
> > = application/x-rtp, media=(string)video, payload=(int
> > )104, clock-rate=(int)90000, encoding-name=(string)H264
> > WARNING: from
> > element /GstPipeline:pipeline0/GstRtpH264Depay:rtph264depay0: Could
> > not decode stream.
> > Additional debug info:
> > gstbasertpdepayload.c(368): gst_base_rtp_depayload_chain
> > (): /GstPipeline:pipeline0/GstRtpH264Depay:rtph264depay0:
> > Received invalid RTP payload, dropping
> > WARNING: from
> > element /GstPipeline:pipeline0/GstRtpH264Depay:rtph264depay0: Could
> > not decode stream.
> >
> > I can do this process for MP2T packets. I know that RTP is not a valid
> > 'container' for this but I would think that by isolating the RTP
> > portion of each packet, writing them to a binary file, reading the
> > packets and passing them to the RTP H264 depayloader should address
> > those problems.
> >
> > In attempting to isolate problems, I also captured video from a
> > webcam, H264 encoded it, ran it through the rtph264payloader and wrote
> > it to a file. This same script fails the same way with that file.
> >
> > Can anyone suggest where I have goofed? BTW - ffplay also fails.
> >
> > Thank you,
> > Chuck Crisler
> >
> > _______________________________________________
> > gstreamer-devel mailing list
> > gstreamer-devel at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
> > _______________________________________________
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>
> --
> Olivier Crête
> olivier.crete at collabora.com
>
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