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• FFmpeg Negative Duration [migrated]

  22 septembre 2014, par filby

  i have a large number of small videos (parts of a larger) of the form :

  Metadata:
  
  major_brand     : isom
  
  minor_version   : 512
  
  compatible_brands: isomiso2avc1mp41
  
  encoder         : Lavf55.43.100
  
  Duration: 00:00:05.53, start: -1.831497, bitrate: 3355 kb/s
  
  Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 4760 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
  Metadata:
  
    handler_name    : VideoHandler
  
  Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 157 kb/s (default)
  
  Metadata:
  
    handler_name    : SoundHandler

  I want to completely discard the negative start, the 1.83 seconds, and keep only the 3.67 seconds in the positive ’axis’.

  I cut the videos with the correct duration however i believe due to some sync i did in sound (in the original), resulted in me having a video of 5.53 second, of which 1.83 is audio only, and the last 3.67 seconds are the ones i want to keep (and the ones i did cut).

  In a video player i can watch the 3.67 seconds i want to however if i extract the audio i get +1.83 seconds of audio at start from the original video (from which i cut the parts) which i didnt intend to cut. What can i do ;

  P.S.
  Example of the command i used to cut the part :

  ffmpeg -ss 818 -i input -t 3.67 -codec:v libx264 -profile:v high -preset slow -b:v 5000k -maxrate 5000k -threads 0 -codec:a copy output

• ffmpeg to rip mp3 from mp4 in ruby

  11 septembre 2014, par RichardC

  Trying to make basic Ruby script utilising ffmpeg to download a video from Youtube and then rip the mp3 from that video.
  Problem is each time the script fails when trying to separate the two, even though the command themselves run fine outside of the.
  I think the issue is that Ruby is treating the video as a string, but I’m not sure.

  def input
  
      #print "Enter Video URL: "
  
      #@target_video = gets
  
      #@target_video ||= ''
  
      #@target_video.chomp
  
      @target_video = 'https://www.youtube.com/watch?v=bYG1qccSUAw'
  
  end
  
  
  
  def grab
  
      #@video = `viddl-rb #{@target_video}`
  
      `viddl-rb #{@target_video}`
  
  end
  
  
  
  def rip
  
      `ffmpeg -i #{grab} new.mp3`
  
  end
  
  
  
  input
  
  rip

  I tested it in irb and when I tried @video.class it returned string, I think this is where it’s going wrong but I’m not certain.
  The video does download successfully but fails on teh rip.

  Output and error :

  ruby youtube_downloader.rb 
  
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
  
                                   Dload  Upload   Total   Spent    Left  Speed
  
  100 30.4M  100 30.4M    0     0  2580k      0  0:00:12  0:00:12 --:--:-- 2683k
  
  ffmpeg version 2.3.3 Copyright (c) 2000-2014 the FFmpeg developers
  
    built on Aug 25 2014 19:47:15 with Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.3.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid
  
    libavutil      52. 92.100 / 52. 92.100
  
    libavcodec     55. 69.100 / 55. 69.100
  
    libavformat    55. 48.100 / 55. 48.100
  
    libavdevice    55. 13.102 / 55. 13.102
  
    libavfilter     4. 11.100 /  4. 11.100
  
    libavresample   1.  3.  0 /  1.  3.  0
  
    libswscale      2.  6.100 /  2.  6.100
  
    libswresample   0. 19.100 /  0. 19.100
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Loading: No such file or directory
  
  sh: line 1: Plugins: command not found
  
  sh: line 2: Will: command not found
  
  sh: line 3: Analyzing: command not found
  
  sh: line 4: Using: command not found
  
  sh: line 5: [YOUTUBE]: command not found
  
  sh: line 6: [YOUTUBE]: command not found
  
  sh: line 7: Using: command not found
  
  sh: line 8: Download: command not found
  
  sh: line 9: Error:: command not found
  
  sh: line 11: Backtrace:: command not found
  
  sh: -c: line 12: syntax error near unexpected token `:27:in'
  
  sh: -c: line 12: `(eval):27:in `initialize''

• Streaming a video to /dev/video0 using gstreamer and v4l2 shows a black screen [on hold]

  24 septembre 2019, par Lawliet

  I’ve been trying to use a video as a webcam for quite a while now. The command

  gst-launch-1.0 filesrc location=newflag.webm ! decodebin ! videoconvert ! v4l2sink device=/dev/video0

  Using this command, i’m able to watch the stream using VLC but Discord and Firefox display a black screen when using /dev/video0 as a webcam.

  I got it working using ffmpeg to stream the video in yuv420p so I suspect videoconvert converts the stream to YUY2 which is I guess not supported by Discord nor Firefox.

  Any idea on how to get this to work ?