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• how to convert any audio file to wav on server side with node.js [on hold]

  9 juin 2014, par pufmaigre

  my dear stackoverflow

  I spent hours looking for an efficient and pretty way to transcode audio on server side, and I found a lot of informations... actually too much informations.

  Sox for Node.js looks fine but there are not so much documentation, I was unable to convert a mp3 to wav with it :

  https://www.npmjs.org/package/sox

  Then fluent ffmpeg sounds good but I have the feeling I will loose a lot of time to achieve my goal with it :

  https://github.com/fluent-ffmpeg/node-fluent-ffmpeg

  and then i found some more obscure stuff like those ones :

  https://github.com/andrewrk/node-plan-transcode

  https://github.com/benvanik/node-transcoding

  I’m not sure it’s really the "stackoverflow spirit" but I’m asking you wich way would you choose to achieve my goal because I’m feeling lost in the codec jungle.

  thanks in advance !! love :)

• Rotate mp4 videos without re-encoding

  6 juillet 2024, par stedes

  I'm looking for a way to rotate videos shot with my Nexus 4 on my Debian Wheezy sytem. The videos are shot in portrait mode and I would like to rotate them to landscape mode. Preferably the rotation is command-line driven.

  



  I have found several previous questions which are hinting at a good solution but I can't seem to manage to get it working.

  



  To begin with there was this question :
Rotating videos with FFmpeg

  



  But it indicates that ffmpeg is outdated and that I should use avconv. I found this question detailing the way to go forward.
https://askubuntu.com/questions/269429/how-can-i-rotate-video-by-180-degrees-with-avconv

  



  This made me using following command :

  



  avconv -i original.mp4 -vf "transpose=1" -codec:v libx264 -preset slow -crf 25 -codec:a copy flipped.mp4


  



  However, this is painstakingly slow (last test took me more than 6 hours for less than 3 minutes of footage) and does not result in a playable movie. I also get an error in logging output which states Mb Rate > level limit.

  



  Is there an issue here with the re-encoding ? Should I first re-encode the videos from my phone to another, more "workable" encoding before applying the rotations ? Or am I missing another important point ?

  


• ffplay / ffmpeg with audio and video filters

  20 juillet 2018, par user10104150

  i tried to modify a already existing code for ffplay for hours, but I could not get it.
  I could not find a manual for vertical and horizontal stacking parameters. I’m always getting invalid argument errors when I try to adopt it to my needs.
  So I’m asking here for help.

  My idea is based on that : ffplay / ffmpeg setup table with audio and video filters

  The working code that I modified a little but want to modify further without luck is :

  ffplay -f lavfi \
  
           "amovie=in.mp4,asplit=3[sv][eb][av]; \
  
            [sv]showvolume=b=4:f=0:ds=log:c=VOLUME:w=720:h=68[sv-v]; \
  
            [eb]ebur128=video=1:size=720x540:meter=18[eb-v][out1]; \
  
            [av]avectorscope=s=720x540:zoom=1.3:rc=2:gc=200:bc=10:rf=1:gf=8:bf=7[av-v]; \
  
            [sv-v][eb-v][av-v]vstack=3[1c]; \
  
            movie=in.mp4,split=4[v][wf][wfc][vs]; \
  
            [wf]waveform=m=1:d=0:r=0:c=7[wf-vus]; \
  
            [wf-vus][v]scale2ref=iw:1220-ih[wf-va][sig]; \
  
            [wf-va]setsar=1[wf-v]; \
  
            [wfc]waveform=m=0:d=0:r=0:c=7,scale=610x610,setsar=1[wfc-v]; \
  
            [vs]vectorscope=m=color3:g=color,scale=610x610,setsar=1[vs-v]; \
  
            [sig][wf-v]vstack[2c]; \
  
            [wfc-v][vs-v]vstack[3c]; \
  
            [1c][2c][3c]hstack=3,scale=1920:-1[out0]"

  I’d like to change it to that style - I’m not yet allowed to post images directly in this question, so I need to link it :

  Link to image how I’d like the layout to be

  I’d like to have the video shown in 1920x1080 (keeping aspect ratio, downscale if necessary).