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µStreamer

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µStreamer is a lightweight and very quick server to stream MJPEG video from any V4L2 device to the net. All new browsers have native support of this video format, as well as most video players such as mplayer, VLC etc. µStreamer is a part of the Pi-KVM project designed to stream VGA and HDMI screencast hardware data with the highest resolution and FPS possible.

µStreamer is very similar to mjpg-streamer with input_uvc.so and output_http.so plugins, however, there are some major differences. The key ones are:

Feature µStreamer mjpg-streamer
Multithreaded JPEG encoding
Hardware image encoding
on Raspberry Pi
Behavior when the device
is disconnected while streaming
Shows a black screen
with NO SIGNAL on it
until reconnected
✘ Stops the streaming 1
DV-timings support -
the ability to change resolution
on the fly by source signal
Partially yes 1
Option to skip frames when streaming
static images by HTTP to save the traffic
2
Streaming via UNIX domain socket
Systemd socket activation
Debug logs without recompiling,
performance statistics log,
access to HTTP streaming parameters
Option to serve files
with a built-in HTTP server
Regular files only
Signaling about the stream state
on GPIO using libgpiod
Access to webcam controls (focus, servos)
and settings such as brightness via HTTP
Compatibility with mjpg-streamer's API :)

Footnotes:

  • 1 Long before µStreamer, I made a patch to add DV-timings support to mjpg-streamer and to keep it from hanging up no device disconnection. Alas, the patch is far from perfect and I can't guarantee it will work every time - mjpg-streamer's source code is very complicated and its structure is hard to understand. With this in mind, along with needing multithreading and JPEG hardware acceleration in the future, I decided to make my own stream server from scratch instead of supporting legacy code.

  • 2 This feature allows to cut down outgoing traffic several-fold when streaming HDMI, but it increases CPU usage a little bit. The idea is that HDMI is a fully digital interface and each captured frame can be identical to the previous one byte-wise. There's no need to stream the same image over the net several times a second. With the --drop-same-frames=20 option enabled, µStreamer will drop all the matching frames (with a limit of 20 in a row). Each new frame is matched with the previous one first by length, then using memcmp().


TL;DR

If you're going to live-stream from your backyard webcam and need to control it, use mjpg-streamer. If you need a high-quality image with high FPS - µStreamer for the win.


Building

You'll need make, gcc, libevent with pthreads support, libjpeg9/libjpeg-turbo and libbsd (only for Linux).

  • Arch: sudo pacman -S libevent libjpeg-turbo libutil-linux libbsd.
  • Raspbian: sudo apt install libevent-dev libjpeg8-dev libbsd-dev. Add libgpiod-dev for WITH_GPIO=1 and libsystemd-dev for WITH_SYSTEMD=1.
  • Debian/Ubuntu: sudo apt install build-essential libevent-dev libjpeg-dev libbsd-dev.
  • Alpine: sudo apk add libevent-dev libbsd-dev libjpeg-turbo-dev musl-dev. Build with WITH_PTHREAD_NP=0.

To enable GPIO support install libgpiod and pass option WITH_GPIO=1. If the compiler reports about a missing function pthread_get_name_np() (or similar), add option WITH_PTHREAD_NP=0 (it's enabled by default). For the similar error with setproctitle() add option WITH_SETPROCTITLE=0.

$ git clone --depth=1 https://github.com/pikvm/ustreamer
$ cd ustreamer
$ make
$ ./ustreamer --help

AUR has a package for Arch Linux: https://aur.archlinux.org/packages/ustreamer.

FreeBSD port: https://www.freshports.org/multimedia/ustreamer.


Usage

For M2M hardware encoding on Raspberry Pi, you need at least 5.15.32 kernel. OpenMAX and MMAL support on older kernels is deprecated and removed.

Without arguments, ustreamer will try to open /dev/video0 with 640x480 resolution and start streaming on http://127.0.0.1:8080. You can override this behavior using parameters --device, --host and --port. For example, to stream to the world, run:

# ./ustreamer --device=/dev/video1 --host=0.0.0.0 --port=80

Please note that since µStreamer v2.0 cross-domain requests were disabled by default for security reasons. To enable the old behavior, use the option --allow-origin=\*.

The recommended way of running µStreamer with Auvidea B101 on Raspberry Pi:

$ ./ustreamer \
    --format=uyvy \ # Device input format
    --encoder=m2m-image \ # Hardware encoding on V4L2 M2M driver
    --workers=3 \ # Workers number
    --persistent \ # Don't re-initialize device on timeout (for example when HDMI cable was disconnected)
    --dv-timings \ # Use DV-timings
    --drop-same-frames=30 # Save the traffic

Please note that to use --drop-same-frames for different browsers you need to use some specific URL /stream parameters (see URL / for details).

You can always view the full list of options with ustreamer --help.


Raspberry Pi Camera Example

Example usage for the Raspberry Pi v1 camera:

$ sudo modprobe bcm2835-v4l2
$ ./ustreamer --host :: -m jpeg --device-timeout=5 --buffers=3 -r 2592x1944

Please note that newer camera models have a different maximum resolution. You can see the supported resolutions at the PiCamera documentation.

If you get a poor framerate, it could be that the camera is switched to photo mode, which produces a low framerate (but a higher quality picture). This is because bcm2835-v4l2 switches to photo mode at resolutions higher than 1280x720. To work around this, pass the max_video_width and max_video_height module parameters like so:

$ modprobe bcm2835-v4l2 max_video_width=2592 max_video_height=1944

Integrations

Janus

µStreamer supports bandwidth-efficient streaming using H.264 compression and the Janus WebRTC server. See the Janus integration guide for full details.

Nginx

When uStreamer is behind an Nginx proxy, it's buffering behavior introduces latency into the video stream. It's possible to disable Nginx's buffering to eliminate the additional latency:

location /stream {
    postpone_output 0;
    proxy_buffering off;
    proxy_ignore_headers X-Accel-Buffering;
    proxy_pass http://ustreamer;
}

Tips & tricks for v4l2

v4l2 utilities provide the tools to manage USB webcam setting and information. Scripts can be use to make adjustments and run manually or with cron. Running in cron for example to change the exposure settings at certain times of day. The package is available in all Linux distributions and is usually called v4l-utils.

  • List of available video devices: v4l2-ctl --list-devices.
  • List available control settings: v4l2-ctl -d /dev/video0 --list-ctrls.
  • List available video formats: v4l2-ctl -d /dev/video0 --list-formats-ext.
  • Read the current setting: v4l2-ctl -d /dev/video0 --get-ctrl=exposure_auto.
  • Change the setting value: v4l2-ctl -d /dev/video0 --set-ctrl=exposure_auto=1.

Here you can find more examples. Documentation is available in man v4l2-ctl.


See also


License

Copyright (C) 2018-2022 by Maxim Devaev mdevaev@gmail.com

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.