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• Revision 35436 : Petites pétouilles en passant par là (écriture aux dernières normes ...

  22 février 2010, par marcimat@… — Log

  Petites pétouilles en passant par là (écriture aux dernières normes ISO)…

• ffmpeg - how to handle video and audio URL's streams separately ?

  13 mai 2022, par Rubem Pacelli

  I am trying to create a zsh function that uses youtube-dl and ffmpeg to download a portion of a YouTube video. I did achieve this goal with the following function :

  


  # $1 - youtube URL
# $2 - start position in hh:mm:ss.msms format (ms=miliseconds)
# $3 - final position in hh:mm:ss.msms format (ms=miliseconds)
# $4 - output file name (optional)
function youtubedl_snippet()(
  local url_stream=$(youtube-dl -f best --get-url $1)
  local output_name=$(youtube-dl --get-title $1)

  ffmpeg -ss $2 -to $3 -i $url_stream -c:v copy -c:a copy ${4:-"$output_name.mp4"}
)


  


  The command youtube-dl -f best --get-url $1 return a single URL with the best possible quality. In order to understand better how ffmpeg works, I tried to create another function with the same goal but with a different approach :

  


  # $1 - youtube URL
# $2 - start position in hh:mm:ss.msms format (ms=miliseconds)
# $3 - final position in hh:mm:ss.msms format (ms=miliseconds)
# $4 - output file name (optional)
# $5 - output video codec type (optional, for instance: libx264)
# $6 - output audio codec type (optional, for instance: aac)
function youtubedl_snippet2()(
  local url_streams=$(youtube-dl --get-url $1)
  local output_name=$(youtube-dl --get-title $1)

  local url_array=(${(f)url_streams}) # expand urls by lines url_array[1] -> video stream url_array[2] -> audio stream

  ffmpeg -ss $2 -to $3 -i ${url_array[1]} -ss $2 -to $3 -i ${url_array[2]} -map 0:v -map 1:a -c:v ${5:-copy} -c:a ${6:-copy} ${4:-"$output_name.mp4"}
)


  


  What I suppose that is going on here :

  


  

  1. url_streams is a line-separated URL. url_array[1] is the video URL and url_array[2] is the audio URL.

  


  2. I am setting both audio and video to the same intervals.

  


  3. I mapped the first stream to video, and the second to audio

  


  4. If $5 and $6 does not give different codecs, ffmpeg just copy from the original source.

  


  


  Well, it seems that everything is ok. But when I try

  


  start=$SECONDS; youtubedl_snippet2 'https://www.youtube.com/watch?v=g-_hVXzkn0o' 00:00:05.00 00:00:15.00; echo "it takes $(( SECONDS - start )) seconds"


  


  It will take 368 seconds. Moreover, I cannot open it in my android (only audio works)

  


  

  


  On the other hand,

  


  start=$SECONDS; youtubedl_snippet 'https://www.youtube.com/watch?v=g-_hVXzkn0o' 00:00:05.00 00:00:15.00; echo "it takes $(( SECONDS - start )) seconds"


  


  takes only 40 seconds, and the video can be played on Android.

  


  Here is the youtubedl_snippet log file. And here is the youtubedl_snippet2 log file.

  


• run ffmpeg commands from my own project

  28 octobre 2013, par bruno

  I'm starting a project where I want ppl to upload videos of a talk and a the video of slides for that talk and want to merge them (to play at the same time) and then show results.

  My question is :
  Is it possible to do that from code ? if it is, can you point me to the right doc ?
  I was able to do it running command line, but as I want this to run on a server with different ppl uploading their videos I think this would not be the best approach.
  I have a preference for Java if it's possible to do it, but I can manage to use other languages what do you guys suggest ?

  The idea would be to have a service where I can point the urls of the videos stored in my server and it would merge them and save file where I can later stream. With different ppl uploading videos at the same time and being able to watch the result in a reasonable amount of time.

  I used this tutorial to test :
  https://trac.ffmpeg.org/wiki/Create%20a%20mosaic%20out%20of%20several%20input%20videos

  Thanks for your time