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• Anomalie #2460 (Fermé) : L’onglet « Ajouter des plugins » a disparu en rév. [18808] et [18813]

  16 décembre 2011, par cedric -

  il est normal que cette fonctionnalité ait disparu du core. C’est le plugin SVP qui la prendra en charge.

• Encoding parameters in videos for web (low in size) while keeping quality good enough ?

  10 juillet 2012, par umutto

  I'm trying to build a video sharing platform much like youtube. So far everything is going great, but i'm having difficulties with my encoding parameters in ffmpeg. I'm using a silverlight media player so the output file must be in wmv format.

  The only thing i can play freely was -qscale parameter and it gets shabby after 8. And i downloaded some youtube videos and they seem to keep amazing quality (definitely not -qscale 8 can achieve) with very low file sizes.

  So what i'm asking is some patterns that can help me convert a video to high, mid and low quality wmv videos.

  The codec i use right now is pretty simple and useless is like this ; (oh btw audio must keep 128k or higher quality for mid and high)

     ffmpeg -i a1.wmv -vcodec wmv2 -qscale 2 -s 852x480 -acodec wmav2 -ar 44100 -ab 128k -y a480.wmv
  
     ffmpeg -i a1.wmv -vcodec wmv2 -qscale 4 -s 640x360 -acodec wmav2 -ar 44100 -ab 128k -y a360.wmv
  
     ffmpeg -i a1.wmv -vcodec wmv2 -qscale 6 -s 354x200 -acodec wmav2 -ar 44100 -ab 128k -y a200.wmv

  the output quality i achieve with this command is more than enough but the sizes are usually 10 times larger than a youtube video near the same or less quality.

  Thanks in advance !

• Non-monotonous DTS when concatenate slowed down video

  23 janvier 2019, par whynotbealion

  Copy from Video StackExchange

  I try to concatenate multiple videos to achieve the following :

  All my videos are in mp4 format.
  One video is first slowed down, then mixed with audio
  Videos are concatenated in the following order : Normal video, normal video, slowed-down video (output.mp4), normal video ...
  The video is slowed down with the following command :

  ffmpeg -y -i raw.mp4 -filter:v 'setpts=1.3333*PTS' silent.mp4

  Audio is added with the following command :

  ffmpeg -y -i silent.mp4 -i audio.mp3 -map 0:0 -map 1:0 output.mp4

  When I concatenate using the Concat demuxer (https://trac.ffmpeg.org/wiki/Concatenate) the audio of the output is not in sync with the video. During the concatenation I get the "Non-monotonous DTS" error.

  I tried the following

  Following this suggestion (https://video.stackexchange.com/a/22941/24238) after I created my slowed down and mixed video (output.mp4) I convert all mp4 videos to mts format. After this I concatenate and with

  ffmpeg -i fullvideo.mts fullvideo.mp4

  I convert the resulting video back to mp4 format. This video plays just fine, but during the convert again I get the following error "Non-monotonous DTS in output stream 0:1 ; previous : 191803, current : 187633 ; changing to 191804. This may result in incorrect timestamps in the output file."

  My question

  Even regardless the error the video plays just fine, even in the browser. Does this solution still have a disadvantage or threat ? Is there a better solution where I don’t get any DTS error ?
  I am thankful for any help as this is all new for me.