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• Call system package with Go on App Engine Standard

  8 novembre 2019, par reidreid46

  I’m trying to use FFmpeg in a Go application thats running on Google App Engine Standard. I can get this to run locally, when I point to a local instance of the FFmpeg binary using exec.Command()

  cmd := exec.Command(
  
      "/Users/justin/Desktop/conversion/ffmpeg", // this won't work on a remote server
  
      "-i", "pipe:0",
  
      "-ac", "1",
  
      "-codec:a", "libmp3lame",
  
      "-b:a", "48k",
  
      "-ar", "24000",
  
      "-f", "mp3",
  
      "pipe:1",
  
    )
  
  
  
    cmd.Stdin = bytes.NewReader(synthResp.AudioContent)
  
  
  
    var output bytes.Buffer
  
    cmd.Stdout = &output
  
    err = cmd.Run()

  Obviously, this won’t work when I deploy the application, so I need a way to point to a hosted version of the FFmpeg binary. It seems ffmpeg is a system package for the go1.11 App Engine Standard environment.

  What are "System packages" and how do I use them ?
  When I look for documentation, I find a lot of documentation on apt-get, and no documentation on how to use them, App Engine or otherwise. Do I need to install it, or should it already be part of the container(?) that App Engine is running ?

  Do I call it, like I’d call other executables ? If so, that I’d expect this to work, but it doesn’t

  cmd := exec.Command(
  
      "ffmpeg", // <------ what should this be?
  
      "-i", "pipe:0",
  
      "-ac", "1",
  
      "-codec:a", "libmp3lame",
  
      "-b:a", "48k",
  
      "-ar", "24000",
  
      "-f", "mp3",
  
      "pipe:1",
  
    )
  
  
  
    cmd.Stdin = bytes.NewReader(synthResp.AudioContent)
  
  
  
    var output bytes.Buffer
  
    cmd.Stdout = &output
  
    err = cmd.Run()

  Logging err, I see exec: "ffmpeg": executable file not found in $PATH

• ffmpeg - convert image sequence to video with reversed order

  8 avril 2017, par 0__

  Looking at the docs, it is not apparent to me whether ffmpeg would allow me to convert an image sequence to a video in reverse order, for example using this sequence :

  frame-1000.jpg
  
  frame-999.jpg
  
  frame-998.jpg
  
  ...
  
  frame-1.jpg

  Is it possible to give a "step direction" for the frame indices ?

• Ideal bitrates for different video resolutions

  15 octobre 2018, par Ramesh Navi

  I am building a Video-on-demand service for a closed community. I using FFMPEG for video processing and dash.js for adaptive bitrate player with custom resolution selector. Can somebody please suggest what ideal bitrates should I use while video/audio transcoding ?

  I am talking about -b:v and -ab option

  ffmpeg -i vid.mp4 -c:v libvpx-vp9 -keyint_min 150 \
  
  -g 150 -tile-columns 4 -frame-parallel 1  -f webm -dash 1 \
  
  -an -vf scale=144:-1 -b:v 120k -dash 1 video_1.webm \
  
  -an -vf scale=240:-1 -b:v 250k -dash 1 video_2.webm \
  
  -an -vf scale=360:-1 -b:v 500k -dash 1 video_3.webm \
  
  -an -vf scale=480:-1 -b:v 750k -dash 1 video_4.webm \
  
  -an -vf scale=720:-1 -b:v 1500k -dash 1 video_5.webm

  And

  ffmpeg -i vid.mp4 -vn -acodec libvorbis -ab 96k -dash 1 audio_96k.webm

  Any suggestions/hacks or examples to tackle real-world network situations are appreciated.