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• Split a video file into separate video and audio files using a single ffmpeg call ?

  25 novembre 2015, par sdaau

  Background : I would like to use MLT melt to render a project, but I’d like that render to result with separate audio and video files. I’d intend to use melt’s "consumer" avformat which uses ffmpeg’s libraries, so I’m formulating this question as for ffmpeg.

  According to Useful FFmpeg Commands For Converting Audio & Video Files (labnol.org), the following is possible :

  ffmpeg -i video.mp4 -t 00:00:50 -c copy small-1.mp4 -ss 00:00:50 -codec copy small-2.mp4

  ... which slices the "merged" audio+video files into two separate "chunk" files, which are also audio+video files, in a single call ; that’s not what I need.

  Then, ffmpeg Documentation (ffmpeg.org), mentions this :

  ffmpeg -i INPUT -map_channel 0.0.0 OUTPUT_CH0 -map_channel 0.0.1 OUTPUT_CH1

  ... which splits the entire duration of the content of two channels of a stereo audio file, into two mono files ; that’s more like what I need, except I want to split an A+V file into a stereo audio file, and a video file.

  So I tried this with elephantsdream_teaser.ogv :

  ffmpeg -i /tmp/elephantsdream_teaser.ogv \
  
    -map 0.0 -vcodec copy ele.ogv -map 0.1 -acodec copy ele.ogg

  ... but this fails with "Number of stream maps must match number of output streams" (even if zero-size ele.ogv and ele.ogg are created).

  So my question is - is something like this possible with ffmpeg, and if it is, how can I do it ?

• Load processed video instead of original video - Rails, Dragonfly

  1er février 2016, par Michael B

  In my Rails 4-Project, I am using Dragonfly to upload images and videos.
  For image-processing I use imagemagick, for videoprocessing I use ffmpeg.

  Videos are uploaded and stored in the folder uploads/videos. After processing, they are stored in public/ffmpeg_videos/

  My question is : How can I use the processed-video instead of the uploaded video ?

  e.g. I use this code in the view, to display a video :

  <video src="&lt;%=@video.video.url%>"></video>

  This successfully loads the original video from the upload-path. But what do I have to change, to load the video from the ffmpeg-path ?

  initializers/dragonfly.rb

  require 'dragonfly'
  
  
  
  # Configure
  
  Dragonfly.app(:images).configure do
  
    plugin :imagemagick
  
    protect_from_dos_attacks false
  
    secret 'd045734b043b4383a246c5c8daf2d3e31217dc8b030f21861e4fd16c4b72d382'
  
    url_format '/media/:job/:name'
  
  
  
    datastore :file,
  
              root_path: Rails.root.join('uploads/images/'),
  
              server_root: Rails.root.join('uploads')
  
  end
  
  
  
  Dragonfly.app(:videos).configure do
  
    secret 'd045734b043b4383a246c5c8daf2d3e31217dc8b030f21861e4fd16c4b72d382'
  
    url_format "/video/:job/:name"
  
  
  
    datastore :file,
  
              root_path: Rails.root.join('uploads/videos/'),
  
              server_root: Rails.root.join('uploads')
  
  end
  
  
  
  # Logger
  
  Dragonfly.logger = Rails.logger
  
  
  
  # Mount as middleware
  
  Rails.application.middleware.use Dragonfly::Middleware, :images
  
  Rails.application.middleware.use Dragonfly::Middleware, :videos
  
  
  
  # Add model functionality
  
  if defined?(ActiveRecord::Base)
  
    ActiveRecord::Base.extend Dragonfly::Model
  
    ActiveRecord::Base.extend Dragonfly::Model::Validations
  
  end

• Saving Raw Uncompressed Video Files using OpenCv, Gstreamer, and/or FFMPEG ?

  20 septembre 2022, par adav0033

  I have been trying to implement the cv::VideoWriter function from OpenCV to generate a an uncompressed (raw) video file. I started this because of a statement within the OpenCV Documentation which I will link here along with the statement.

  


  cv::VideoWriter::VideoWriter    (   const String &  filename,
int     fourcc,
double  fps,
Size    frameSize,
bool    isColor = true 
)       


  


  "If FFMPEG is enabled, using codec=0 ; fps=0 ; you can create an uncompressed (raw) video file."

  


  Ref. https://docs.opencv.org/3.4/dd/d9e/classcv_1_1VideoWriter.html

  


  However whilst troubleshooting the function I came across the refuting statement,

  


  " VideoCapture and VideoWriter do not provide interface to access raw compressed video stream, except maybe MJPEG in some cases.
Make sure you actually use FFmpeg backend by setting apiPreference parameter : VideoWriter("outfile.avi", cv2.CAP_FFMPEG, ...)"

  


  Ref. https://github.com/opencv/opencv/issues/14573

  


  I am now confused about how I go about writing the cv::VideoWriter function to satisfy the requirements to create a raw uncompressed video file (.avi) and if it is even possible. If it is not possible how do I achieve the outcome of saving an raw uncompressed video file, as I assume it would use some combination of FFMPEG, OpenCV,or Gstreamer.

  


  Note : My code is implemented in c++