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I want to learn more about synchronization of different streams with RTCP with Gstreamer. A video was divided into 4 parts vertically so that synchronization can be better observed at the receiver. Following are the codes used for sender and receiver.

sender:

gst-launch -v \
\
gstrtpbin name=rtpbin1 \
filesrc location=/home/chinthaka/Desktop/MageHeenaye101.avi ! decodebin ! x264enc ! rtph264pay ! rtpbin1.send_rtp_sink_0 \
rtpbin1.send_rtp_src_0 ! udpsink host=192.168.1.100 port=5011 \
rtpbin1.send_rtcp_src_0 ! udpsink host=192.168.1.100 port=5012 \
udpsrc port=5013 ! rtpbin1.recv_rtcp_sink_0 \
\
gstrtpbin name=rtpbin2 \
filesrc location=/home/chinthaka/Desktop/MageHeenaye102.avi ! decodebin ! x264enc ! rtph264pay ! rtpbin2.send_rtp_sink_0 \
rtpbin2.send_rtp_src_0 ! udpsink host=192.168.1.100 port=5021 \
rtpbin2.send_rtcp_src_0 ! udpsink host=192.168.1.100 port=5022 \
udpsrc port=5023 ! rtpbin2.recv_rtcp_sink_0 \
\
gstrtpbin name=rtpbin3 \
filesrc location=/home/chinthaka/Desktop/MageHeenaye103.avi ! decodebin ! x264enc ! rtph264pay ! rtpbin3.send_rtp_sink_0 \
rtpbin3.send_rtp_src_0 ! udpsink host=192.168.1.100 port=5031 \
rtpbin3.send_rtcp_src_0 ! udpsink host=192.168.1.100 port=5032 \
udpsrc port=5033 ! rtpbin3.recv_rtcp_sink_0 \
\
gstrtpbin name=rtpbin4 \
filesrc location=/home/chinthaka/Desktop/MageHeenaye104.avi ! decodebin ! x264enc ! rtph264pay ! rtpbin4.send_rtp_sink_0 \
rtpbin4.send_rtp_src_0 ! udpsink host=192.168.1.100 port=5041 \
rtpbin4.send_rtcp_src_0 ! udpsink host=192.168.1.100 port=5042 \
udpsrc port=5043 ! rtpbin4.recv_rtcp_sink_0

Receiver:

gst-launch -v \
videomixer name=mix ! ffmpegcolorspace ! autovideosink sync=false async=false \
\
gstrtpbin name=rtpbin1 \
udpsrc port=5011 caps = "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, sprop-parameter-sets=(string)\"Z01AFeygbCPNLgIgAAADAC7msoAB4sWywA\\=\\=\\,aOvssg\\=\\=\", payload=(int)96, ssrc=(uint)861153369, clock-base=(uint)4026289255, seqnum-base=(uint)30449" ! rtpbin1.recv_rtp_sink_0 rtpbin1. ! rtph264depay ! queue ! ffdec_h264 ! videobox border-alpha=0 top=0 left=0 ! mix. \
udpsrc port=5012 ! rtpbin1.recv_rtcp_sink_0 \
rtpbin1.send_rtcp_src_0 ! udpsink port=5013 host=192.168.1.104 \
\
gstrtpbin name=rtpbin2 \
udpsrc port=5021 caps = "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, sprop-parameter-sets=(string)\"Z01AFeygbCPNLgIgAAADAC7msoAB4sWywA\\=\\=\\,aOvssg\\=\\=\", payload=(int)96, ssrc=(uint)861153369, clock-base=(uint)4026289255, seqnum-base=(uint)30449" ! rtpbin2.recv_rtp_sink_0 rtpbin2. ! rtph264depay ! queue ! ffdec_h264 ! videobox border-alpha=0 top=-120 left=0 ! mix. \
udpsrc port=5022 ! rtpbin2.recv_rtcp_sink_0 \
rtpbin2.send_rtcp_src_0 ! udpsink port=5023 host=192.168.1.104 \
\
gstrtpbin name=rtpbin3 \
udpsrc port=5031 caps = "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, sprop-parameter-sets=(string)\"Z01AFeygbCPNLgIgAAADAC7msoAB4sWywA\\=\\=\\,aOvssg\\=\\=\", payload=(int)96, ssrc=(uint)861153369, clock-base=(uint)4026289255, seqnum-base=(uint)30449" ! rtpbin3.recv_rtp_sink_0 rtpbin3. ! rtph264depay ! queue ! ffdec_h264 ! videobox border-alpha=0 top=-240 left=0 ! mix. \
udpsrc port=5032 ! rtpbin3.recv_rtcp_sink_0 \
rtpbin3.send_rtcp_src_0 ! udpsink port=5033 host=192.168.1.104 \
\
gstrtpbin name=rtpbin4 \
udpsrc port=5041 caps = "application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264, sprop-parameter-sets=(string)\"Z01AFeygbCPNLgIgAAADAC7msoAB4sWywA\\=\\=\\,aOvssg\\=\\=\", payload=(int)96, ssrc=(uint)861153369, clock-base=(uint)4026289255, seqnum-base=(uint)30449" ! rtpbin4.recv_rtp_sink_0 rtpbin4. ! rtph264depay ! queue ! ffdec_h264 ! videobox border-alpha=0 top=-360 left=0 ! mix. \
udpsrc port=5042 ! rtpbin4.recv_rtcp_sink_0 \
rtpbin4.send_rtcp_src_0 ! udpsink port=5043 host=192.168.1.104

I can receive the 4 videos in the same video, but synchronization of each streams is not perfect.

  • I just used the same caps for all the receivers. Just found out that caps generated at each time is different at the sender. Is there a good way to send the caps generated to the receiver so that same caps can be used at the receiver?

  • Is there any best way to synchronize multiple streams using RTCP?

  • Here different ports are used for different RTP and RTCP sessions. Is it advisable or should I use only two ports, one for RTP and one for RTCP.

Please kindly advice. I am quite new to the Gstreamer and trying my best to get familiar with the synchronization.

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1 回答 1

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我强烈建议您改为在代码中开始执行此操作。启动线非常适合原型设计，但是当涉及到像同步这样的细粒度控制时，您应该改用代码。

GStreamers rtpbin 可以很好地处理 RTCP 同步。如果两个或多个流具有相同的 cname，它将计算（使用 RTCP）在发送方看到的这些流之间的相对时间戳差异，然后使用 gstrtpjitterbuffers ts-offset 在接收方上复制它。理论上，如果您的媒体在发送时是同步的，那么您也应该能够在接收器处同步渲染它。

于 2013-06-26T22:12:57.810 回答