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• Displaying text on video while recording and if saved then also (add text to video when start recording)

  25 novembre 2017, par J4GD33P 51NGH

  i’m using this android project from git hub and now want to add text to video when start recording. text should also there if we watch saved video later. can anyone suggest me an idea to do this.

• Displaying text on video while recording and if saved then also(add text to video when start recording)

  25 novembre 2017, par J4GD33P 51NGH

  i’m using this android project from git hub and now want to add text to video when start recording. text should also there if we watch saved video later. can anyone suggest me an idea to do this.

• Issue with MJPEG stream playback speed when encoding with FFmpeg

  6 janvier, par Arciiix

  I'm working with a MJPEG stream source

  


  Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 1280x720 [SAR 1:1 DAR 16:9], 25 tbr, 25 tbn

  


  I want to capture this stream and save it to an MP4 file using FFmpeg, but I am running into a weird issue.

  


  The only way it works fine is when I just copy the stream without reencoding and using wallclock as timestamps (cmd 1) :

  


  ffmpeg -use_wallclock_as_timestamps 1 -i "http://IP/video/1280x720" -c:v copy output_good.mp4


  


  However, when I try encoding the stream with libx264, the playback speed of the resulting video becomes slower than 100%, causing the video to gradually fall out of sync with real-time. This happens even when I use any encoding, also when I explicitly set the frame rate or vsync. For example, these commands fail :

  


  

  • CMD 2 : ffmpeg -i "http://IP/video/1280x720" -c:v libx264 -r 30 -preset fast output_bad1.mp4

  


  • CMD 3 : ffmpeg -use_wallclock_as_timestamps 1 -i "http://IP/video/1280x720" -c:v libx264 output.mp4

  


  


  https://www.youtube.com/watch?v=PF0fuCu7Xao

  


  As you can see in the comparison of the resulting videos, the playback gradually slows down with CMD 2 and CMD 3, while it's alright with CMD 1.

  


  What I've noticed is that on the FFmpeg stdout, when using encoding, the speed= and FPS= go up and up, e.g. to 31 FPS even though my source is technically at 25 FPS.

  


  What I've tried :

  


  

  • different encoding codecs (e.g. libvpx)

  


  • -re

  


  • preset ultrafast on encoding

  


  • vsync (fps_mode), both ctr and vfr

  


  • fps=30 filter

  


  


  Has anyone encountered a similar issue or know how to force FFmpeg to preserve the correct playback speed while encoding or enforcing a frame rate ? Thanks !