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• avfilter : add grayworld video filter

  28 août 2021, par Paul Buxton

  avfilter : add grayworld video filter
  Implements a gray world color correction algorithm
  
  using a log scale LAB colorspace.
  Signed-off-by : Paul Buxton <paulbuxton.mail@googlemail.com>
  
  Signed-off-by : Paul B Mahol <onemda@gmail.com>
  

  • [DH] Changelog
  • [DH] doc/filters.texi
  • [DH] libavfilter/Makefile
  • [DH] libavfilter/allfilters.c
  • [DH] libavfilter/version.h
  • [DH] libavfilter/vf_grayworld.c

• DrawText and crossfade effect - ffmpeg

  22 juillet 2018, par Geek

  I have one video with crossfade effect and i want add text on this video (drawtext).
  However when i add a filter text, he remove a crossfade effect in the final video.

  Command to create video with crossfade effect :

  ffmpeg -i first.mp4 -i second.mp4 -filter_complex 
  
      "[0:v]trim=start=0:end=2,setpts=PTS-STARTPTS[0_clip_1];
  
      [0:v]trim=start=2:end=3,setpts=PTS-STARTPTS[fadeoutsrc_0];
  
      [fadeoutsrc_0]format=pix_fmts=yuva420p,fade=t=out:st=0:d=1:alpha=1[fadeout_0];
  
      [fadeout_0]fifo[fadeoutfifo_0];[1:v]trim=start=1,setpts=PTS-STARTPTS[1_clip_2];
  
      [1:v]trim=start=0:end=1,setpts=PTS-STARTPTS[fadeinsrc_1];
  
      [fadeinsrc_1]format=pix_fmts=yuva420p,fade=t=in:st=0:d=1:alpha=1[fadein_1];
  
      [fadein_1]fifo[fadeinfifo_1];
  
      [fadeoutfifo_0][fadeinfifo_1]overlay[crossfade_1];
  
      [0_clip_1][crossfade_1][1_clip_2]concat=n=3[output];[0:a][1:a] acrossfade=d=1 [audio]" 
  
  -map "[output]" -map "[audio]" videoWithCrossfade.mp4

  Command to add filter text :

  ffmpeg -i videoWithCrossfade.mp4 -filter_complex 
  
      "/Windows/fonts/arial.ttf':text='hello world!':fontcolor=white:fontsize=40:box=1:boxcolor=red
  
      @0.5:boxborderw=10:x=500:y=500"
  
      output.mp4

  this is the link of video : http://www.mediafire.com/file/kw3lvdb2rp1bs6u/videoWithCrossfade.mp4/file
  http://www.mediafire.com/file/iycdzozsqzosq87/output.mp4/file

  Thanks for your help !

• Is ffmpeg able to read ArrayBuffer input from stream

  7 juillet 2017, par jAndy

  I want to accomplish the following tasks :

  • Record Video+Audio from any HTML5 (MediaStream) capable browser
  • Send that data via WebSocket as Blob / ArrayBuffer chunks to a server
  • Broadcast that input stream-data to multiple clients

  As it turns out, this brought me into a world of pain. The first task is fairly simple using the HTML5 MediaStream objects alongside WebSockets.

  // ... for simplicity...
  
  navigator.mediaDevices.getUserMedia({ audio: true, video: true }).then(stream => {
  
      let mediaRecorder = new MediaRecorder( stream );
  
      // ...
  
      mediaRecorder.ondataavailable = e => {
  
          webSocket.send( 'newVideoData', e.data ); // configured for binary data
  
      };
  
  });

  Now, I want to receive those data fragments and stream those via nginx vod module, because I guess I want the output stream in HLS or DASH.
  I could write a little nodejs script as backend, which just receives the binary chunks and write them to a file or stream, and just reference it so nginx vod module could possibly read it and create the m3u8 manifest on the fly ?

  I am wondering now,

  • if ffmpeg is able to read that binary data directly (should be webm format), without a man-in-the-middle script, "somehow" ?
  • If not, do I have to write the data down into a file and pass that as input to ffmpeg or can I (should I) pipe the data to a self spawned ffmpeg instance ? (if so, how ?)
  • Do I actually need the nginx server (probably alongside rtmp module) to deliver the output stream as HLS or could I just use ffmpeg to also create a dynamic manifest ?
  • Is the nginx vod module capable of creating a dynamic hls/dash manifest or must the input data be complete beforehand ?
  • Ultimately, am I on the totally wrong track here ? :P

  Actually I just want to create a little video-live-chat demo, without any plugins or 3rd party encoding software, pure browser.