Video-Pis

Research-documentation for H264-encoding and streaming with Raspberry Pis.

• max. supported resolution: 1080p30. Theoretically CSI-2 with two lanes should be capable of handling 1080p50 in UYVY colorspace, but this fails so far, even as UYVY seems to be in use. (It's unclear if everything will literally melt, too ;)
• The iframe-peroid of 2 frames is quiet aggressive.
• I/O-mode = auto. Result unclear, it seems popular stating DMAbuf here. Investigate!

Since 2020 there is an implementation of SMPTE 2022-1 in gstreamer, done in MPEGTS via UDP with 2D-FEC: blog-post by Mathieu.

Documentation: rtpst2022-1-fecdec, rtpst2022-1-fecenc

• Tested by wtf with an Raspberry Pi 4B+ with Raspberry Pi OS 2023-10-10, Debian Bookworm each, in March 2024.
• Works per multicast as well as per unicast.
• Latency: ca. 1 second
• Receiver needs a static route towards 224.0.0.0/4 on eth0 in order to receive multicast.
• Receiver needs to be started before (first) launch of sender. Help needed! Issue at Mathieu.
• Don't forget to remove “netsim drop-probability=0.01” before flight!

Sender, using Audio from HDMI-In and sending video-input to display:

gst-launch-1.0  \
    rtpbin name=rtp fec-encoders='fec,0="rtpst2022-1-fecenc\ rows\=4\ columns\=4";' \
      v4l2src device=/dev/video0 io-mode=0 do-timestamp=true ! "video/x-raw,framerate=30/1,format=UYVY,colorimetry=bt601" ! \
      tee name=input ! \
      v4l2h264enc output-io-mode=0 extra-controls="controls,h264_profile=4,h264_level=11,video_bitrate=15000000,video_bitrate_mode=0,h264_i_frame_period=2;" ! \
      "video/x-h264,profile=high, level=(string)4" ! h264parse ! \
      mpegtsmux name=mux ! rtpmp2tpay ssrc=0 ! rtp.send_rtp_sink_0  \
        rtp.send_rtp_src_0 ! udpsink host=${ipAddress} port=5000 multicast-iface=eth0 \
        rtp.send_fec_src_0_0 ! udpsink host=${ipAddress} port=5002 async=false multicast-iface=eth0 \
        rtp.send_fec_src_0_1 ! udpsink host=${ipAddress} port=5004 async=false multicast-iface=eth0 \
      alsasrc device=hw:tc358743 do-timestamp=true ! audio/x-raw,format=S16LE,rate=48000,channels=2 ! \
      audioconvert ! voaacenc bitrate=48000 ! aacparse ! queue ! mux. \
      input. ! queue ! videoconvert ! fbdevsink device="/dev/fb0" sync=false  

Receiver, with audio-out on Headphone-jack:

gst-launch-1.0 \
  rtpbin latency=100 fec-decoders='fec,0="rtpst2022-1-fecdec\ size-time\=100000000";' name=rtp \
  udpsrc address=224.0.23.1 port=5002 caps="application/x-rtp, payload=96" ! queue ! rtp.recv_fec_sink_0_0 \
  udpsrc address=224.0.23.1 port=5004 caps="application/x-rtp, payload=96" ! queue ! rtp.recv_fec_sink_0_1 \
  udpsrc address=224.0.23.1 port=5000 caps="application/x-rtp, media=video, clock-rate=90000, encoding-name=mp2t, payload=33" ! \
    queue ! netsim drop-probability=0.01 ! rtp.recv_rtp_sink_0 \
  rtp. ! queue ! decodebin name=decode  ! videoconvert ! queue !  kmssink \
  decode. ! audioconvert ! queue ! alsasink card-name="bcm2835 Headphones"

• Tested by wtf with an Raspberry Pi 4B+ with Raspberry Pi OS 2023-10-10, Debian Bookworm each, in March 2024.
• Latency: ca. 0.7 seconds
• SRT-desired latency is with 40ms VERY aggressive! The suggested value is 2.5 times the round-trip-time (RTT) between both hosts.
• starting/restarting-order seems strange and needs to be investigated.

Sender, using Audio from HDMI-In and sending video-input to display:

gst-launch-1.0 -v \
  v4l2src device=/dev/video0 io-mode=0 do-timestamp=true ! "video/x-raw,framerate=30/1,format=UYVY,colorimetry=bt601" ! \
  tee name=input ! \
  v4l2h264enc output-io-mode=0 extra-controls="controls,h264_profile=4,h264_level=11,video_bitrate=15000000,video_bitrate_mode=0,h264_i_frame_period=2;" ! \
  "video/x-h264,profile=high, level=(string)4" ! \
  mpegtsmux name=mux ! srtsink uri=srt://:8888 latency=40 mode=listener wait-for-connection=true \
  input. ! queue ! videoconvert ! fbdevsink sync=false \
  alsasrc device=hw:tc358743 do-timestamp=true ! audio/x-raw,format=S16LE,rate=48000,channels=2 ! audioconvert ! voaacenc bitrate=48000 ! aacparse ! queue ! mux. 
  

Receiver, with audio-out on Headphone-jack:

gst-launch-1.0 \
  srtclientsrc latency=20 mode=caller uri=srt://${ipAddress}:8888 ! \
  tsdemux latency=40 name=demux demux. ! queue ! decodebin name=decode ! videoconvert ! queue ! kmssink \
  demux. ! queue ! avdec_aac ! audioconvert ! alsasink card-name="bcm2835 Headphones"