1 Overview[edit source]
This article will explain how to stream camera content over network thanks to GStreamer application on top of V4L2 Linux® kernel framework.
Capturing compressed JPEG pictures is an efficient way to send camera images to any local or remote player; JPEG pictures require a limited bandwidth while being fully interoperable.
Find below some examples of command lines allowing to capture a continuous JPEG stream while playing it using various multimedia players, either local or remote.
2 Local streaming[edit source]
Here is an example of a local preview involving V4l2-ctl for JPEG pictures capture and gst-play GStreamer player for JPEG decoding and display. JPEG pictures are sent over a standard Linux pipe.
For STM32MP135 line  , setup the camera subsystem first:
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media-ctl -d /dev/media0 --set-v4l2 "'ov5640 1-003c':0[fmt:JPEG_1X8/640x480@1/30 field:none]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_parallel':0[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':0[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':1[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':1[crop:(0,0)/640x480]" |
Capture JPEG pictures then decode & display them:
v4l2-ctl --set-parm=30;v4l2-ctl --set-fmt-video=width=640,height=480,pixelformat=JPEG --stream-mmap --stream-count=-1 --stream-to=- 2>/dev/null | gst-play-1.0 "fd://0"
--stream-to=- tells V4l2-ctl to output binary captured content to standard output, which is then sent to pipe |.
Special URI fd://0 tells gst-play GStreamer player to read data from the pipe.
Note the 2>/dev/null right after the V4l2-ctl command to remove the logs from console output.
3 UDP streaming[edit source]
An internet connection is required, for example by plugging an ethernet cable on the:
STM32MP135x-DK Discovery kit 
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CN4 Ethernet connector 1 or CN15 Ethernet connector 2 |
| STM32MP157x-DKx Discovery kit
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CN8 Ethernet connector |
| STM32MP157x-EV1 Evaluation board
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CN3 Ethernet connector |
| For STM32MP135 line , setup the camera subsystem first:
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media-ctl -d /dev/media0 --set-v4l2 "'ov5640 1-003c':0[fmt:JPEG_1X8/640x480@1/30 field:none]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_parallel':0[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':0[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':1[fmt:JPEG_1X8/640x480]" media-ctl -d /dev/media0 --set-v4l2 "'dcmipp_dump_postproc':1[crop:(0,0)/640x480]" |
Get the IP address aa.bb.cc.dd of the host PC using ifconfig command:
ifconfig | grep "inet addr"
inet addr:aa.bb.cc.dd Bcast:10.201.23.255 Mask:255.255.252.0
inet addr:127.0.0.1 Mask:255.0.0.0
Then fill the host= udpsink property with this IP address on the remote side:
v4l2-ctl --set-parm=30;v4l2-ctl --set-fmt-video=width=640,height=480,pixelformat=JPEG --stream-mmap --stream-count=-1 --stream-to=- 2>/dev/null | gst-launch-1.0 fdsrc ! jpegparse ! rtpjpegpay ! udpsink host=aa.bb.cc.dd port=5000
Then play the UDP stream on host PC:
gst-launch-1.0 udpsrc port=5000 ! application/x-rtp, encoding-name=JPEG ! rtpjpegdepay ! jpegparse ! decodebin ! autovideosink
A new window will popup on host PC displaying the camera content.
