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• FFmpeg - How to trim with high precision ?

  11 octobre 2016, par DSalenga

  I am pretty stucked with the way that FFmpeg trims videos, so I would be really grateful if someone could help me.
  Basically, what I am trying to do is : I have a video sequence and I want it to stop in a certain second, freeze the image some seconds (like a pause), and then reproduce again from the same exact frame. I could say that I am dealing with three videos : A.mp4 (first part of the video sequence), B.mp4 (frozen image) and C.mp4 (second part of the video sequence). Besides, I also perform an overlay with filter_complex.

  The part of generating a video from a static image is not a problem, my main concern is to find the way to trim and concatenate videos accurately. From other posts and sources, I discovered that FFmpeg trims from those Frames that are Keyframes, which can be forced. However, the result I obtain is not the appropriate one, because my video A ends in a frame different from the one in the beginning of C.

  The commands I am using are the following ones :

  ffmpeg -y -i VideoSequence.mp4 -c:v libx264 -pix_fmt yuv420p \
  
  -force_key_frames "expr: gte(t,n_forced * 15)" -t 30 VideoOut.mp4

  [Note that everything inside Filter Complex is about an Overlay, which works fine]

  As far as I know, the resulting video should have a Keyframe every 15 seconds. Now, I want to cut the video into 2 parts ("before second 15" and "after second 15") :

  ffmpeg -y -ss 00:00:01 -i VideoOut.mp4 -t 14 -c copy A.mp4
  
  
  
  ffmpeg -y -ss 00:00:15 -i VideoOut.mp4 -t 5 -c copy C.mp4 

  As mentioned, I expect the end of A.mp4 to "match" with the beginning of C.mp4 (at a frame precision), but the result I obtain is far from being perfect.

  Thank you very much, any kind of help will be appreciated !

• Ffmpeg hls live stream video freezes for a second but audio continues and video catches up

  13 décembre 2022, par Bluchip Studio

  I am using the latest version of ffmpeg to create a hls live stream todo this i am using the following command

  


  /root/ffmpeg -y -loglevel debug -threads 0 -probesize 512000 -analyzeduration 512000 -user_agent "Chrome/98.0.4758.102" -i https://example.com/input.m3u8 -c:v copy -c:a copy -async 1 -tune zerolatency -fflags +genpts -hls_init_time 2.002 -hls_time 2.002 -hls_list_size 20 -hls_flags delete_segments+append_list -hls_segment_type mpegts -hls_segment_filename "/var/www/html/hls/segment_%05d.ts" -f hls "/var/www/html/hls/playlist.m3u8"


  


  I initially tried using fmp4 but i noticed the video would lag behind major and the audio would end up well ahead so i switched to mpegts

  


  i managed to fix the audio issue here using -async 1 on fmp4 this made no diffrence now i have a small issue where my stream will open and play but the video will freez every few seconds while the audio continues and then the video will jump to catch back up and continue then it will do it again and again and again

  


  dose anyone know what may be causing this issue i tried swapping to x264 in stead of copying the video stream and using force key frames to set a key frame every 2 seconds but this resulted in well the same issue if not a little worse

  


  i kind of expected the stream to play perfect with the settings i have and with the logs set to debug i cant see any errors at all

  


• The Ultimate YouTube-DL script [on hold]

  30 juillet 2018, par G. L.

  I need help creating/finishing a bash script. What I’m trying to do is to create the perfect YouTube-DL archiving script.
  As of now, the only thing I can do is download all of a Users’ videos, embed subtitles, add metadata but I want to also autosub the files (with script number 2) and convert the downloaded files with ffmpeg or AVConv or handbrake-cli and then remove the video files when I have a successful conversion.

  Script 1 (downloads videos skipping already downloaded ones)

  youtube-dl -i -o "%(title)s-%(id)s.%(ext)s" --all-subs --embed-subs --embed-thumbnail --add-metadata --sleep-interval=20 --rate-limit=1M --exec 'youtube-dl2kodi.py -t tvshow -f {}' --download-archive .archive $(cat url.txt) 

  Note : youtube-dl2kodi.py creates Kodi compatible nfo files so I can view them properly on Kodi with metadata.

  Script 2 (subtitles videos automatically using autosub)

  for file in *I WANT TO AUTOSUB files in this directory and subdirectories*
  
  do
  
    autosub -S de -D de "$file" >> results.out
  
  done

  I want to merge script 1 and 2 and then encode the files and remove original video files (mp4, mkv and webm) if successful.
  My encoding preference is HEVC with CRF 23 and I don’t want to encode the audio. I want to copy the audio. The final video would be a MKV file.