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• Anomalie #4052 : Visualiser ses messages dans le privé

  28 novembre 2017, par tcharlss (*´_ゝ｀)

  J’ai bien ce lien sur contrib, spip.net et forum. C’est tout en bas de la boîte d’infos :

  AUTEUR NUMÉRO
  6944
  Je suis rédacteur
  
  4 articles
  
  24 messages de forum
  
  Voir en ligne
  

• ffmpeg : Audio out of sync after conversion mp4 -> DNxHD

  7 février 2019, par Daniel E

  Based on this post I used the command :

  ffmpeg -i input.mp4 -c:v dnxhd -vf "scale=1280:720,fps=29.90,format=yuv422p" -b:v 110M -c:a pcm_s16le output.mov

  to convert an mp4 file to mov with the dnxhd video codec. I also want the pcm_s16le audio codec.

  Here you can see the input file’s properties :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'mexico-raw-combined.mp4':                                                                                                                                             
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512 
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.23.101
  
    Duration: 00:49:59.01, start: 0.000000, bitrate: 17220 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 16961 kb/s, SAR 1:1 DAR 16:9, 29.90 fps, 29.92 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandle
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 249 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandle

  And here are the output file’s properties :

   Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 512
  
      compatible_brands: qt  
  
      encoder         : Lavf58.12.100
  
    Duration: 00:49:59.01, start: 0.000000, bitrate: 111235 kb/s
  
      Stream #0:0(eng): Video: dnxhd (DNXHD) (AVdn / 0x6E645641), yuv422p(tv, bt709/unknown/unknown), 1280x720, 109733 kb/s, SAR 1:1 DAR 16:9, 29.90 fps, 29.90 tbr, 19136 tbn, 19136 tbc (default)
  
      Metadata:
  
        handler_name    : DataHandler
  
        encoder         : Lavc58.18.100 dnxhd
  
      Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
  
      Metadata:
  
        handler_name    : DataHandler

  The issue is that towards the end of the output file (keep in mind it’s a 50 min video) the audio ends a bit ahead of the video, and the last 1 min 10 seconds are silent for some reason.

  Also note that I chose a framerate of 29.9 fps because that’s what the input file uses.

• ffmpeg slows down as I run it

  14 septembre 2022, par Bambi2k21

  I edit a video such that it speeds up by 8x where the speaker is silent and by 2x when he is speaking. And to do that I use ffmpeg in such a manner :

  


  ffmpeg -i C:\Users\TheD4\Desktop\uni1.mp4 -filter_complex "[0:v]trim=0:0.98,setpts=1*(PTS- 
STARTPTS)[v0]; [0:a]atrim=0:0.98,asetpts=PTS-STARTPTS,atempo=1[a0] 
[0:v]trim=0.98:1.598,setpts=0.5*(PTS-STARTPTS)[v1]; [0:a]atrim=0.98:1.598,asetpts=PTS- STARTPTS,atempo=2[a1]; [0:v]trim=1.598:1.946,setpts=1*(PTS-STARTPTS)[v2]; 
[0:a]atrim=1.598:1.946,asetpts=PTS-STARTPTS,atempo=1[a2]; [0:v]trim=1.946:1.975,setpts=0.5*(PTS- 
STARTPTS)[v3]; [0:a]atrim=1.946:1.975,asetpts=PTS-STARTPTS,atempo=2[a3];............ 
[0:v]trim=1529.04:1537.34,setpts=1*(PTS-STARTPTS)[v1652]; [0:a]atrim=1529.04:1537.34,asetpts=PTS- 
STARTPTS,atempo=1[a1652]; [0:v]trim=1537.34:1537.55,setpts=0.5*(PTS-STARTPTS)[v1653]; 
[0:a]atrim=1537.34:1537.55,asetpts=PTS-STARTPTS,atempo=2[a1653]; 
[0:v]trim=1537.55:1538.73,setpts=1*(PTS-STARTPTS)[v1654]; [0:a]atrim=1537.55:1538.73,asetpts=PTS- 
STARTPTS,atempo=1[a1654]; [0:v]trim=1538.73:1539.15,setpts=0.5*(PTS-STARTPTS)[v1655]; 
[0:a]atrim=1538.73:1539.15,asetpts=PTS-STARTPTS,atempo=2[a1655]; [v0][a0][v1][a1][v2][a2][v3] 
[a3]..........[v1652][a1652][v1653][a1653][v1654][a1654][v1655][a1655]concat=n=1656:v=1:a=1" -preset 
superfast -profile:v baseline


  


  But the thing is, as you might have noticed the filter goes into the thousands, and so the total number of caracters is high(in this example there are around 200000), but cmd(8000) or powershell(30000) have less than that. So to get around that limitation, I divided all of that into smaller parts, but here is where the problem starts, as I run more and more of the "parts code" and ffmpeg does work on later and later parts of the video, the process of making the video from those smaller parts becomes slower as well, even though the size of the video is the same. To see what is wrong, I ran the code from a couple of hundred seconds(so instead of starting from 0s it start from let's say 500s) and I noticed the same effect. So what I think happens is that ffmpeg goes through the entirety of the video until it reaches the specified start. So here is my question is there a way to tell ffmpeg to ignore the start of the video and to start immediately from where I need it to, maybe something like this :

  


  ffmpeg -i C:\Users\TheD4\Desktop\uni1.mp4[500:] -filter_complex ........