web video and video stream tapping 'how-to'

notes/Video-Streaming-Notes.md

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+Video Streaming Notes
+===
+
+Install dependencies and create `/dev/video1`:
+
+```
+apt-get install -y motion v4l2loopback-utils v4l2loopback-source
+modprobe v4l2loopback
+```
+
+Update `motion.conf`:
+
+```
+$ mkdir -p $HOME/log
+$ cat <<EOF > $HOME/.motion/motion.conf
+stream_port 8080
+stream_quality 98
+stream_maxrate 25
+framerate 10
+stream_localhost off
+output_pictures off
+framerate 30
+ffmpeg_video_code mpeg4
+width 320
+height 240
+auto_brightness off
+contrast 0
+saturation 0
+text_right ''
+videodevice /dev/video1
+log_file /home/pi/log/motion.log
+EOF
+```
+
+Motion will, by default, look in `~/.motin/motion.conf` for the config file.
+
+A simple video passthrough can be used to test to make sure everything is working:
+
+```
+ffmpeg -re -f v4l2 -i /dev/video0 -r 11 -q 3 -f avi - | ffmpeg -re -f avi -i - -f v4l2 /dev/video1
+```
+
+After starting `motion`, and pointing a browser to the `motion` port that's been setup (`8080`),
+a 320x240 video feed should be seen.
+
+---
+
+Once the simple test has been done, a more complex example can be done with OpenCV that
+puts an overlay onto the image.
+
+Here is a simple OpenCV Python program to put some text and an alpha blended box into
+the middle of the stream.
+Call it `ocv2-overlay-cap.py`:
+
+```
+#!/usr/bin/python
+#
+import sys
+import cv2
+import numpy as np
+foreground = np.ones((100,100,3),dtype='uint8')*255
+cap = cv2.VideoCapture(0)
+#cap.set(cv2.cv.CV_CAP_PROP_FRAME_WIDTH, 320)
+#cap.set(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT, 240)
+cap.set(cv2.CAP_PROP_FRAME_WIDTH, 320)
+cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 240)
+alpha = 0.4
+while True:
+  ret, background = cap.read()
+  #background = cv2.flip(background,1)
+  added_image = cv2.addWeighted(background[100:200,100:200,:],alpha,foreground[0:100,0:100,:],1-alpha,0)
+  background[100:200,100:200] = added_image
+  font = cv2.FONT_HERSHEY_SIMPLEX
+  #cv2.putText(background,'alpha:{}'.format(alpha),(10,30), font, 1,(255,255,255),2,cv2.CV_AA)
+  cv2.putText(background,'alpha:{}'.format(alpha),(10,30), font, 1,(255,255,255),2,cv2.LINE_AA)
+  sys.stdout.write( background.tostring() )
+cap.release()
+cv2.destroyAllWindows()
+```
+
+Now to run:
+
+```
+python ./ocv2-overlay-cap.py | \
+  ffmpeg -f rawvideo -pixel_format bgr24 -video_size 320x240 -i - -f avi -speed 10 -q 3 -r 11  -fflags nobuffer - | \
+  ffmpeg -f avi -i - -f v4l2 /dev/video1
+```
+
+This will create a 320x240 feed with a simple overlay of text and a box.
+
+Run `motion` and then point your browser to `localhost:8080`.
+
+Misc.
+---
+
+I was getting some errors when trying to load `cv2` from python.
+The following solved the issue:
+
+```
+apt update
+apt upgrade
+reboot
+```
+
+---
+
+Different qualities can be fed in to try and speed up the video with the `-q`, `-r` and `-speed` parameters.
+Some have been chosen above but they can be altered depending on what quality of video and what playback
+speed is desired.
+
+---
+
+The `motion` parameters in `motion.conf` can be added to save to output files:
+
+```
+output_pictures on
+picture_output on
+```
+
+---
+
+The `motion` parameter, `stream_localhost`, in `motion.conf` should be set to `off` to ensure
+only `localhost` streaming can occur:
+
+```
+stream_localhost on
+```
+
+
+References
+---
+
+* [SO: OpenCV Python, reading video from named pipe](https://stackoverflow.com/questions/35166111/opencv-python-reading-video-from-named-pipe)
+* [GH: How to read a video frame from a pipe, for Opencv #120](https://github.com/kkroening/ffmpeg-python/issues/120)
+* [SO: How to stream a local video to webcam using ffmpeg?](https://unix.stackexchange.com/questions/466663/how-to-stream-a-local-video-to-webcam-using-ffmpeg)
+* [Add image to a live camera feed using OpenCV-Python](https://theailearner.com/2019/03/18/add-image-to-a-live-camera-feed-using-opencv-python/)
+* [How to find frame rate or frames per second (fps) in OpenCV ( Python / C++ ) ?](https://www.learnopencv.com/how-to-find-frame-rate-or-frames-per-second-fps-in-opencv-python-cpp/)
+* [How to set cv2.VideoCapture() image size in Python](https://techoverflow.net/2018/12/18/how-to-set-cv2-videocapture-image-size/)
+* [GH: v4l2loopback](https://github.com/umlaeute/v4l2loopback)
+* [SO: Is there any way ffmpeg send video to /dev/video0 on Ubuntu?](https://askubuntu.com/questions/881305/is-there-any-way-ffmpeg-send-video-to-dev-video0-on-ubuntu)
+* [ffmpeg capture/webcam](https://trac.ffmpeg.org/wiki/Capture/Webcam)
+* [Picamera web streaming](https://picamera.readthedocs.io/en/release-1.13/recipes2.html#web-streaming)
+* [Motion: Output - Pipe Options](https://motion-project.github.io/motion_config.html#OptDetail_Pipe)
+* [Making a video with opencv and ffmpeg. How to find the right color format?](https://stackoverflow.com/questions/12503368/making-a-video-with-opencv-and-ffmpeg-how-to-find-the-right-color-format)
+