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• How to rotate an image overlay in ffmpeg around the image center ?

  14 mars 2023, par ktrace

  I'm using ffmpeg to scale, rotate and overlay an image on a video. I'm able to rotate the image by the desired angle but the overlay ends up being moved both vertically and horizontally from the expected position.

  


  The commands I've tried and their corresponding outputs are shown below. Command 1 gives the expected output, 2 and 3 do not.

  


  How can I modify my commands in general, to rotate the overlay image around the image center, to get the expected output ?

  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=0:c=none:ow=rotw(0):oh=roth(0)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=0.8017360589297406:c=none:ow=rotw(0.8017360589297406):oh=roth(0.8017360589297406)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=5.493783719179012:c=none:ow=rotw(5.493783719179012):oh=roth(5.493783719179012)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  Links to input files :

  


  

  • graphpaper.mp4 https://imgur.com/a/daHI7j0

  


  • arrow.png https://imgur.com/a/wWwnnfq

  


  


• Using ffmpeg without hardware acceleration (C++)

  13 février 2018, par MadMarky

  I’m working on an application (c++/Linux) that uses the ffmpeg 3.4 libraries to do video encoding. Since version 3.3 hardware acceleration is enabled by default if the platform supports it. The graphics card in my dev system has hardware acceleration support, but the tool also has to run on older systems that do not.
  How can i configure ffmpeg to disable hardware acceleration for video encoding ? There is a ton of info about enabling, but i just cant find how to disable it.

  ps.
  There already is a similar question : How to turn off ffmpeg hardware acceleration but its a year old and unfortunately still unanswered.

• How to implement live video streaming with ffmpeg without using WebRTC ?

  8 août 2024, par Artem

  Following up on my previous question, I'd like to inquire about alternative methods for live video streaming using ffmpeg (WebRTC is not an option due to certain constraints I prefer not to discuss here).

  


  Context :

  


  I have a Go application where a goroutine launches ffmpeg to process a video stream, which is then delivered to the main goroutine via a chan []byte. I tried using WebSocket, but encountered issues as described in the previous question. HLS also didn't work well due to significant latency and artifacts like green squares on the video.

  


  Based on a comment in the previous question, I attempted to stream the video via a simple GET request. Here's the Go handler I implemented :

  


  func stream(helperApp agent.Helper) func(rw http.ResponseWriter, rr *http.Request) {
   a := atomic.Bool{}
   return func(rw http.ResponseWriter, rr *http.Request) {
      if !a.CAS(false, true) {
         http.Error(rw, "already running", http.StatusInternalServerError)
         return
      }

      rw.Header().Set("Access-Control-Allow-Origin", "*")
      rw.Header().Set("Content-Type", "video/mp2t")

      out := make(chan []byte)

      // create StreamParam
      go ScreenCaptureForLiveStream(StreamParam, out) // ffmpeg process starts inside

      r, w := io.Pipe()
      go func() {
         for data := range out {
            w.Write(data)
            fmt.Println(len(data))
         }
      }()
      io.Copy(rw, r)
   }
}



  


  On the client side (HTML) :

  


  <video muted="muted" src="http://localhost:8080/stream" controls="controls"></video>&#xA;

  


  In the browser console, I can see data being received, but the video doesn't play.

  


  FFmpeg is executed with these parameters :

  


  -loglevel error -f avfoundation -framerate 5 -capture_cursor 1 -capture_mouse_clicks 1 -i 1 -c:v libx264 -pix_fmt yuv420p -vf pad='ceil(iw/2)*2:ceil(ih/2)*2' -threads 0 -preset veryfast -bf 2 -f mpegts pipe:1



  


  For validation, I ran :

  


  ffmpeg -i http://localhost:8080/stream -c copy out.mp4



  


  The video was successfully saved and plays.

  


  Question :
What alternative methods exist to implement live video streaming with ffmpeg, aside from WebRTC ? Why does the current approach of streaming video via HTTP GET request not function correctly in the browser, and how can this be resolved ?