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• How to generating waveform from video & show it with video

  25 novembre 2016, par Salil

  We are using Rails as a backend & AngularJS on Front End side in my App where we need to show Video & audio waveform of that video.

  We are using ’wavesurfer.js’ to show the waveform on Front End side & ’node-pcm’ to generate pcm from video file on BackEnd side.

  This is working as expected but in some of the videos while creating waveform from pcm data instead of showing small sine waves we get flat line.
  Also it takes too much time to show the waveform for every page reload.

  To overcome this issue we are planning to create waveform image using ffmpeg

  ffmpeg -i 'https://s3.amazonaws.com/aadasdsadsadasdas/xyz.mp4' -filter_complex showwavespic -frames:v 1 output.png

  This is working fine but it also takes too much time (Ofcourse only once ) to generate the image for remote video (i.e. We are saving videos on S3)

  Problem with this i don’t get any library to integrate the waveform image with the Video.

  Can someone suggest any better approach related to this.

• How to convert a Video to a Slideshow with synced audio ? [closed]

  25 mai 2013, par Henry Mazza

  I want a simple way to convert a Ted Talk Presentation to a SlideShow + (synced)Audio format so I can listen to it in my car. I don't want to lose most of the visuals as it does in the audio format and also want to reduce the storage/cell data needs of the video format.

  So far I already extracted the key scenes with timing and the audio, now I must glue this together in a synced fashion.

  Possible ways I found but couldn't make work :

  • MP4Box to make a .m4b (audiobook/enhanced podcast) with mp4chap to set each image as a chapter image (but I could find proper documentation on how to do this)
  • FFMPEG to make a flat movie with the images (but I couldn't make each image stay for a random period of time)

  Ultimately I will automate this process in my VPS and make my private podcast server, so no fancy tools that don't work in Linux, please.

  EDIT : actually the Podcast is a lousy idea, the artwork must be in a square aspect ratio and has great compatibility problems with varius players. Still studing the Book format.

• ffmpeg generate overlay complex filter for audio with background image

  8 janvier 2016, par user1793606

  I am experimenting with ffmpeg and would like to generate overlay complex filter for audio with background image. The code normally works, except for when adding -filter_complex "[0:a]showwaves=s=1280x720:mode=line,format=yuv420p[v]" -map "[v]" -map 0:a
  it crashes. I found the example code at https://trac.ffmpeg.org/wiki/Waveform Any help is appreciated.

  Command '['c:/ffmpeg/bin\\ffmpeg.exe', '-y', '-loop', '1', '-r', '1', '-i', 'temp\\bg.png', '-i', 'test.mp3', '-filter_complex', '[0:a]showwaves=s=1280x720:mode=line,format=yuv420p[v]', '-map', '[v]', '-map', '0:a', '-c:v', 'libx264', '-preset', 'ultrafast', '-tune', 'stillimage', '-crf', '15', '-pix_fmt', 'yuv420p', '-strict', 'experimental', '-c:a', 'aac', '-b:a', '256k', '-shortest', '-threads', '0', 'done/test.mp4']'

  EDIT 1 :

  I tested this with the new verson : ffmpeg -y -i input.mp3 -i background.png -filter_complex "[0:a]showwaves=s=1280x720:mode=line,format=yuv420p[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy output.mp4

  It generates an output file, but only the waveform, no background included. My end goal is to generate the waveform over the background.