How to stream camera over network

Applicable for

STM32MP13x lines, STM32MP15x lines

---

1. Overview

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

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.

ExpandFor STM32MP135 line , setup the camera subsystem first:

Board $> 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:

Board $> 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

An internet connection is required, for example by plugging an ethernet cable on the:

STM32MP135x-DK unknown board type identifier	CN4 Ethernet connector 1 or CN15 Ethernet connector 2
STM32MP157x-DKx Discovery kit	CN8 Ethernet connector
STM32MP157x-EV1 Evaluation board	CN3 Ethernet connector

ExpandFor STM32MP135 line , setup the camera subsystem first:

Board $> 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:

PC $> 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:

Board $> 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:

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.

Information

Due to SDP protocol signaling, this solution is not fully interoperable because it needs a dedicated GStreamer command line to be played on host side