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• Screen Recording Issues using Python and FFMPEG [closed]

  3 juin, par Kevin McDowell

  I am trying to record a walkthrough of a 3D space contained within a Chrome browser session. The goal is to create deterministic output. If I run this command from a VS Code terminal, it records 30 seconds of video from the window that's about 6MB :

  


  ffmpeg -f gdigrab -framerate 30 -i "title=My3D - Google Chrome" -t 30 "My3D - Google Chrome_screenRecording_v0.mp4"


  


  However, if I call it from Python like so :

  


  subprocess.run("ffmpeg -f gdigrab -framerate 30 -i \"title=My3D - Google Chrome\" -t 15 \"My3D - Google Chrome_screenRecording_v0.mp4\"")


  


  The output video is 30 seconds, but while I can see the mouse moving on the screen, the image is all black and the filesize is only 94KB.

  


  This is on a Windows 11 machine with GPU acceleration disabled in the OS as well as in Chrome. I've also tried it with other web pages and those are also recorded black. Any ideas what is causing this or how to record the screen using Python ?

  


  I've got other alternatives working (using Selenium or PyGet to capture screenshots and then using the VideoWriter class from OpenCV to write them to a video file), but that has a limitation of only about 10 FPS and you can't control the recording time like you can with FFMPEG. If you screen capture for 30 seconds, the actual output may only be 12-18 seconds.

  


• ffmpeg gdigrab offset_x, offset_y and -video_size do not affect output

  15 octobre 2022, par Matthew Basford

  Consider the following javascript string used to run an ffmpeg command that records my screen until q is pressed (including desktop audio)

  


  ffmpeg -probesize 10M -f gdigrab -framerate ${framerate} -i desktop -f dshow -i audio="${audioOutputName}" -offset_x ${left} -offset_y ${top} -video_size ${width}x${height} "tmp/videoshot_raw_${videoshotID}.mp4" -y


  


  And here is an example filled in with some values

  


  ffmpeg -probesize 10M -f gdigrab -framerate 30 -i desktop -f dshow -i audio="VoiceMeeter Output (VB-Audio VoiceMeeter VAIO)" -offset_x 994 -offset_y 231 -video_size 643x256 "tmp/videoshot_raw_5cfc23aa.mp4" -y


  


  The audio and video quality works just fine. I have two monitors and instead of the expected output of an X by Y size video offset by X and Y. All of the video is still intact


  


  I would much prefer to not have to crop the video file in a seperate ffmpeg command, but unless I can figure out why these ffmpeg arguments are not doing as they should, I may have to.

  


  Thank you for reading, and I hope you can help me

  


• creating a jack client from inside a docker container

  19 novembre 2018, par unameuname

  I use jack to route audio between multiple sound cards in my pc.
  To record the audio i use a very convenient FFmpeg command which creates a writable jack client :
  ffmpeg -f jack -i  -strict -2 -y .
  so far this works very well.

  The problem starts here :

  I also have an nginx docker which records my data and makes it available for streaming. when trying to use the same command inside the docker i get the following error :"Unable to register as a JACK client".

  I started to look in to the FFmpeg code and found out that the FFmpeg command calls the jack_client_open command from the jack API, which fails.

  Seems like there is some kind of a problem in the connection between the FFmpeg request from inside the docker to the jackd server running on the host.

  Is there a simple way to create a connection between the two [exposing ports] ?

  (I saw some solutions like netjack2, but before creating a more complex server-client architecture i’d like to find a more elegant solution).

  Thanks for the help !