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• FFmpeg four audiochannels but the first two are static noise

  2 octobre 2014, par sebastian

  I have a handful of videos with one audio stream in which includes four audio channels. I am having trouble in getting the last two channels wherein lies the actual sound. I don’t want to create wave files or anything like that I just want to create a video out of it with the two channels correct channels (three and four). I was thinking about using the -map 0:a:2 and -map 0:a:3 but it does not work quite as well as I had hoped for. Does anyone know a better way or what I am doing wrong ?
  Any help would be appreciated.

  Audio
  
  ID : 2
  
  Format : PCM
  
  Format settings, Endianness : Big
  
  Format settings, Sign : Unsigned
  
  Codec ID : lpcm
  
  Duration : 3mn 54s
  
  Bit rate mode : Constant
  
  Bit rate : 6 144 Kbps
  
  Channel(s) : 4 channels
  
  Sampling rate : 48.0 KHz
  
  Bit depth : 24 bits
  
  Stream size : 172 MiB (3%)
  
  Language : English
  
  Encoded date : UTC 2014-09-25 16:54:09
  
  Tagged date : UTC 2014-09-25 16:55:41

• Ruby Video Upload - Cocaine error when trying to transcode video

  21 janvier 2015, par Scottagecheeze

  I am having a bit of trouble when it comes to transcoding a video being uploaded by Paperclip to S3. I have tried both gem 'paperclip-ffmpeg' and gem 'paperclip-av-transcoder. Both fail when I try to add a new style :

  :styles => {
  
      :medium => { :geometry => "640x480", :format => 'flv' }
  
    }, 
  
    :s3_credentials => {:bucket => ENV['S3_BUCKET_NAME'], :access_key_id => ENV['ACCESS_KEY_ID'], :secret_access_key => ENV['SECRET_ACCESS_KEY']},
  
    :processors => [:ffmpeg],
  
    :path => ":id/:style/:style_:basename.:extension"

  I am able to upload my video as is but I am not able to transcode them. Here is the error that it gives me, sorry for the link, I am not able to post images yet.

  Essentially I want to be able to upload a video in any format and transcode it into a specific format. Any help is greatly appreciated.

  Thanks

• Does the incoming codec or audio-video sync matter when encoding from Xvfb using FFMPEG ?

  15 décembre 2022, par Nav

  How I'm capturing :
  
I'm using Xvfb on Linux, to capture a video and audio from an app that is also running on Linux. I'm using -f x11grab when capturing that video headlessly from Xvfb's frambuffer using FFMPEG, and encoding it using a few other parameters like -c:v libx264 -pix_fmt yuv420p.

  


  The questions :
  
Since I'm reading from Xvfb framebuffer :

  


  

  1. Would it matter that the app uses SVC to encode the video, and I'm using H.264 ?

  


  2. Would it matter if I use a different framerate than the app is using ?

  


  3. Would it matter if I use a different pix_fmt than what the app is using ?

  


  


  Reason for asking :

  


  
  
As shown in the image (blue is the app, red is FFMPEG, green is Xvfb) ;

  


  

  • The CPU percentage consumed by FFMPEG shoots up when the app's CPU percentage shoots up. I've also encountered audio being ahead of video for some participants, but I'm unable to figure out whether it's due to network lag or due to FFMPEG's encoding.

  


  • Also, the aim is to reduce CPU consumption, so I was looking to see if I could do FFMPEG encoding in the same format as the app.