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• Is it possible to use the signalstats YAVG filter in FFMPEG to control the gamma correction in a video ? [migrated]

  27 décembre 2023, par tuqueque

  I don't know if this is even possible, but something tells me it is… You see, I want to dynamically control the gamma correction in FFMPEG/FFPLAY depending on how bright/dark the frame being reproduced in a video/movie is…

  


  For context, there's a filter in FFMPEG/FFPLAY/FFPROBE called signalstats that reports various useful sets of info about the video being processed/reproduced/analized. There's a YAVG parameter in the signalstats filter that returns the average luma level of the frame (https://ffmpeg.org/ffmpeg-filters.html#signalstats-1) . This is what I want to use to determine/calculate the gamma value to use in the eq filter gamma (https://ffmpeg.org/ffmpeg-filters.html#eq)… For example, in the end, I would like to use a formula like "1-(YAVG/50)+1"…

  


  With the signalstats YAVG filter/parameter I've managed to do these unrelated exercises :

  


  Analyze (with FFPROBE) a video and write a log file with the YAVG value for each frame :

  


  ffprobe -f lavfi movie=VIDEO_INPUT,signalstats -show_entries frame_tags=lavfi.signalstats.YAVG -of csv="p=0" > YAVG.log


  


  I have been able to also play a video (with FFPLAY) and show in the upper-left corner the YAVG values for each frame being reproduced :

  


  First, we need to create a text file in the home folder called in this case "signalstat_drawtext.txt" with the following content :

  


      %{metadata:lavfi.signalstats.YAVG}


  


  Then, we run this command :

  


      ffplay VIDEO_INPUT -vf signalstats,drawtext=fontfile=FreeSerif.ttf:fontcolor=lime:textfile=signalstat_drawtext.txt


  


  However, I haven't been able to find/guess how to use the YAVG output to control (in realtime) the gamma value in the eq filter… I think it's possible, I just don't know how to write the command.

  


  Using FFPLAY, I would imagine something like this :

  


  ffplay VIDEO_INPUT -vf signalstats,eq=gamma="1-(metadata:lavfi.signalstats.YAVG/50)+1":eval=frame


  


  But of course, this doesn't work and I'm sure I'm just writing nonsense.

  


• avcodec/qsv : Added look ahead rate control mode

  21 août 2015, par Sven Dueking

  avcodec/qsv : Added look ahead rate control mode
  Reviewed-by : Ivan Uskov <ivan.uskov@nablet.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/qsvenc.c
  • [DH] libavcodec/qsvenc.h
  • [DH] libavcodec/qsvenc_h264.c

• FFMPEG problem when transcoding one after another

  10 juillet 2022, par Mike woods

  In server A, I have a loop to transcode video files one after another to MPEGTS format, And send them to server B. Server B receives the data and broadcast it to multiple clients. I'm using it to broadcast files like a TV channel. Something like this

  


  //Files is an array of multiple video file names

for(file of files) {
  transcode(file);
  //Transcodes and sends the data to server B.
}

//The ffmpeg command that above function is using to transmit the data is
//ffmpeg -y -hide_banner -loglevel error -re -i file_1.mp4 -vcodec libx264 -acodec aac -c:s copy -map 0 -mpegts_flags pat_pmt_at_frames -f mpegts tcp://147.261.97.32


  


  The problem is when I play the stream as a client, it always freezes when first program ends and next one starts. I log the transferred data and data is coming correctly. which means following loop is working and transferring files one after another. But why does it freeze in player ?