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until myserver; do
    echo "Server 'myserver' crashed with exit code $?.  Respawning.." >&2
    sleep 1
done

參考:

https://stackoverflow.com/a/697064/22299707

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update-alternatives --display cuda

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update-alternatives --config cuda

參考:

https://www.baeldung.com/linux/update-alternatives-command
https://then.tw/switch-gcc-versions-with-update-alternatives/

xrdp設定

https://vegastack.com/tutorials/how-to-install-xrdp-server-on-ubuntu-22-04/
https://dic.vbird.tw/linux_server/unit06.php

注意

1. 如果安裝Ubuntu的時候就已經是安裝Desktop版本，就不需要另外安裝xfce
2. 使用遠端桌面的時候，要登入的帳號不可以在遠端的電腦已經登入，因此必須要把AutoLogin關閉

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Host Target
  HostName 192.168.8.71
  User user1
  ProxyJump JumpServer

Host JumpServer
  HostName 192.168.8.149
  User jumpuser

參考

https://city.shaform.com/zh/2017/10/28/ssh-proxycommand/

apt-offline

https://unix.stackexchange.com/questions/694346/transfering-and-offline-installing-net-tools-in-an-ubuntu-server-with-no-interne

https://gist.github.com/ycku/fa3110bce427cf2c1f1ca4a680d594e8#apt-install

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offline$ sudo apt-offline set install.sig --install-packages apache2 libapache2-mod-php
online$ apt-offline get install.sig --threads 5 --bundle install.zip
offline$ sudo apt-offline install install.zip
offline$ sudo apt-get install apache2 libapache2-mod-php

解決方法

https://github.com/docker/for-linux/issues/1187#issuecomment-1570501567

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sudo mkdir /etc/docker
sudo gedit /etc/docker/daemon.json

加入這個屬性

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{
    "features": {"containerd-snapshotter": true}
}

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sudo systemctl restart docker

自動重新下載docker image

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while ! docker pull nvcr.io/nvidia/deepstream:6.4-gc-triton-devel; do sleep .1; done && echo OK

RTP/RTCP

跟TCP和UDP一樣為傳輸層協議
規範RFC3350
RTCP (RTP Control Protocol)專門用來處理服務品質(Qos)
RTP可以選擇用UDP或是TCP來進行傳輸

https://mark-lin.com/posts/20180912/(主要)
http://albert-oma.blogspot.com/2012/05/rtp.html

bps(bit Per Second)

位元率 (bps) = 採樣率(hz) x 採樣大小(bit) x 通道

編碼

將raw檔轉換壓縮

聲音編碼

例如MP3和AAC

色彩顏色編碼RGB與YUV

影像編碼H26X和VPX

主流有H264和VP8

封裝

將聲音和影像編碼後的結果放進容器的過程

容器

用來盛裝編碼，一種編碼可以放進各種容器，例如MP3編碼可以放進.mp3、.mp4、.avi容器裡面

網路協議

https://www.jianshu.com/p/9f3e879a4c9c

DTS和PTS

https://blog.csdn.net/aggie4628/article/details/130440133

Painless Script

https://www.elastic.co/guide/en/elasticsearch/painless/current/painless-walkthrough.html

只選擇夜間的資料

https://stackoverflow.com/a/35596907

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{
  "query": {
    "bool": {
      "filter": [
        {
          "range": {
            "OccurrenceTime": {
              "gte": "2023-12-01",
              "lt": "2024-01-20"
            }
          }
        },
        {
          "script": {
            "script": "doc.OccurrenceTime.value.hour >= 10 && doc.OccurrenceTime.value.hour <= 21"
          }
        }
      ]
    }
  }
}

Here is the minimal steps.
Here is my enviornment

• Windows 10
• Visual Studio Build Tools 2019
• CMake 3.29.0-rc1 (use default install setting)
• Gstreamer:(Use default install setting)
  MSVC 64-bit (VS 2019, Release CRT)
  1.22.10 runtime installer
  1.22.10 development installer
• Python3.8.10

For example, my gstreamer is install in D disk by default.

1. Add System Environment Variable GSTREAMER_ROOT_X86_64 value D:\gstreamer\1.0\msvc_x86_64
   gstreamer doc
2. Add enviornment variable GST_PLUGIN_PATH value D:\gstreamer\1.0\msvc_x86_64\lib\gstreamer-1.0
3. Add Path enviornment variable value D:\gstreamer\1.0\msvc_x86_64\bin
4. re-login the computer
5. create a Python venv and use it
6. pip install --verbose --no-binary opencv-python opencv-python
7. os.add_dll_directory() Shoud be add to code since from Python 3.8+, Python will NOT search DLL from PATH enviornment variable.ref
8. test code

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import os
os.add_dll_directory("D:\\gstreamer\\1.0\\msvc_x86_64\\bin")
import cv2
gst = 'rtspsrc location=rtsp://192.168.8.57/live1s3.sdp timeout= 30000 ! decodebin ! videoconvert ! video/x-raw,format=BGR ! appsink drop=1'

cap = cv2.VideoCapture(gst,cv2.CAP_GSTREAMER)
while(cap.isOpened()):
  ret, frame = cap.read()
  if not ret:
    break
  cv2.imshow('frame', frame)
  if cv2.waitKey(1) & 0xFF == ord('q'):
    break

cv2.destroyAllWindows()
cap.release()

安裝cmake(不一定要裝)

安裝msvc2019 build tool

安裝python3.8.10

設定GSTREAMER_ROOT_X86_64環境變數

gstreamer doc

<gstreamer資料夾>\1.0\msvc_x86_64

直接安裝source distributions版本的opencv-python(opencv 4.3.0之後的版本)

pip install --verbose --no-binary opencv-python opencv-python

GST_PLUGIN_PATH或是GST_PLUGIN_SYSTEM_PATH(不一定要加)

gstreamer預設尋找plugin的順序如下

1. %HOMEDRIVE%%HOMEFOLDER%/.gstreamer-1.0/plugins
2. C:\gstreamer\1.0\x86\lib\gstreamer-1.0
3. ..\lib\gstreamer-1.0
4. %GST_PLUGIN_PATH%
   <gstreamer資料夾>\1.0\msvc_x86_64\lib\gstreamer-1.0

gstreamer doc

Path變數

<gstreamer資料夾>\1.0\msvc_x86_64\bin

載入時手動加入dll路徑

os.add_dll_directory()
ref

測試

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import os
os.add_dll_directory("D:\\gstreamer\\1.0\\msvc_x86_64\\bin")
import cv2
gst = 'rtspsrc location=rtsp://192.168.8.57/live1s3.sdp timeout= 30000 ! decodebin ! videoconvert ! video/x-raw,format=BGR ! appsink drop=1'

cap = cv2.VideoCapture(gst,cv2.CAP_GSTREAMER)
while(cap.isOpened()):
  ret, frame = cap.read()
  if not ret:
    break
  cv2.imshow('frame', frame)
  if cv2.waitKey(1) & 0xFF == ord('q'):
    break

cv2.destroyAllWindows()
cap.release()

gstreamer載入時錯誤檢查

1. 用 Dependencies 軟體檢查dll缺少哪一些東西
2. plugin找不到的錯誤可能是找不到plugin的dll本身，或是找不到plugin所需要的dll

安裝CUDA

CUDA 設定

從4.0之後CUDA相關的功能被移到opencv_contrib，必須要編一opencv_contrib才能啟用CUDA功能

1. set CMAKE_ARGS="-DWITH_CUDA=ON"
2. pip install –verbose –no-binary opencv-contrib-python opencv-contrib-python

(選擇性)G-API

G-API說明
https://github.com/opencv/opencv/wiki/Graph-API

參考

製作Python-package