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• ffmpeg settings for high quality youtube videos [migrated]

  1er avril 2018, par pb.

  I am trying to record short video of my desktop and upload it to youtube.
  The problem is that every time when I upload it to youtube or even dropbox (as video), the quality is much worse.

  My ffmpeg execution :

  ffmpeg -f x11grab -s 1366x768 -r 30 -i :0.0 -codec:v libx264 -crf 10 -bf 20 -flags +cgop -pix_fmt yuv440p -movflags faststart help.mp4

  based on :

  ffmpeg -i <input file="file" /> -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart .mp4

  which I found here

  Original file (.zip) :
  https://www.dropbox.com/s/xlkr83rkqfxon23/help.mp4.zip?dl=0

  File after upload to youtube :
  https://www.youtube.com/watch?v=ewEUgpXOpmg

  As you can see, I loss quality after upload to youtube.

  Could you help me ?
  How should I choose the appropriate parameters to record and upload high quality video ?

• Extract just the audio link from a youtube video without converting

  19 janvier 2017, par kamron shaw

  I know there are hundreds of sites to convert youtube video to mp3. Most of them do it by first downloading the video and then converting it to mp3(or any other audio format) on their server using youtube-dl, ffmpeg or similar programs.

  What I want to know is, is there any way I can just extract the audio link for any youtube video ? I don’t know if it’s possible but I saw a couple of websites doing it .

  First Website : Openaisearch.com
  This website simply gives a download link for the audio(getting it from youtube videos). I searched for a song and saw the download url, it looked something like this :

  https://redirector.googlevideo.com/videoplayback?source=youtube&requiressl=yes&clen=3814013&upn=dzwY9aUVYME&lmt=1469875393441562&expire=1484854959&mime=audio%2Fmp4&nh=IgpwcjAxLnNlYTA5Kg01Mi45NS4yMTYuMTAy&itag=140........... 

  I believe that this is not done by first downloading and converting the video to audio format(Correct me if I am wrong).
  Although the file which gets downloaded after using this link is without any extension, but adding ".m4a" at the end of downloaded file does the work.

  Second Website : http://keepvid.com/ ?url=https ://www.youtube.com/watch?v=PT2_F-1esPk

  Again similar website with similar audio link. You can check by visiting the URL and see link of audio files.

  Any idea how these websites get that "googlevideo.com" link ? Do they scrap the youtube video links or something ?

  Thanks.

• Watch multi-stream video file while being recorded by ffmpeg

  20 janvier 2020, par Luke Gorrie

  I am using ffmpeg to record four 1080p video streams simultaneously and I would like to view these streams in real time while they are being recorded. Ideally I would like to view them from a separate machine, using some convenient Linux data sharing method like ssh/sshfs/..., but that is a nice-to-have. Is there a practical way to accomplish this ?

  The ffmpeg recording command that I currently use is like this :

  ffmpeg \
  
    -f v4l2 -i $cam0 \
  
    -f v4l2 -i $cam1 \
  
    -f v4l2 -i $cam2 \
  
    -f v4l2 -i $cam3 \
  
    -f matroska \
  
    -map 0 \
  
    -map 1 \
  
    -map 2 \
  
    -map 3 \
  
    -c copy \
  
    $output.mkv

  My problem would be solved if I could use a command like ffplay or vlc to play one or more of the video streams, always tracking close to the end of the stream, playing more as data becomes available. I haven’t found such an option though.

  One alternative might be to have the recording ffmpeg process also tile the four 1080p videos into one 4K grid and pipe that to ffplay. Then I could at least preview on the same machine that is recording. I have not been able to work out the right ffmpeg command to do the tiling though and would appreciate an example.