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• c# using pipes to get output stream

  1er janvier 2017, par lilscarecrow

  I am trying to pipe youtube-dl output to ffmpeg as input, but cannot seem to get the piping part to work. In normal cmd, I can do something like

   C:\YT\youtube-dl.exe -o - https://www.youtube.com/watch?v=L4aLQ0ki9Tk | ffmpeg -i pipe:0 -f asf pipe:1 

  but in c# this doesn’t work. Currently, I have c# create 2 processes :

  one for youtube-dl

  C:\YT\youtube-dl.exe -o - https://www.youtube.com/watch?v=L4aLQ0ki9Tk

  and another for ffmpeg

  ffmpeg  -i {yt.StandardOutput} -f s16le -ar 48000 -ac 2 pipe:1

  The problem is with the {yt.StandardOutput} (where yt is the process name of the youtube-dl process and -i specifies the input file/stream). Using pipe:0 doesn’t work either and I am not sure how to link the piped output of the first to the input of the second.

• Architecture of video-based service for mobile phones

  27 juin 2015, par David Azar

  I guess this is more of a conceptual question than a technical one.

  I’m trying to figure out the best way to upload short videos to a server and also be able to download them and watch them on both Android and iOS.

  Lets focus on Android for the moment.

  I’ve done some experiments, and my results have been :

  • I’m able to compress 12-14MB video down to 500KB using FFMPEG lib with pretty good results in quality, but it takes about 12 seconds.

  • Next, im uploading those videos to my Parse backend as ParseFile to store them.

  • Finally, i can download them and watch them with no problem using a VideoView widget.

  Now, for the tests i’ve been running, these are great results. But i want to see if there is a better way to manage and scale all of this.

  My questions are :

  • Is there a better, lighter way to compress video ?

  • Is Parse the right way to go ?

  • How can i stream videos instead of downloading them and storing the on local storage before playing them ? i know this will cause my app to use significant space on disk and i dont want that.

  • How do big companies do this kind of tasks ?

  I’ve heard Amazon S3 is a cool thing for projects like this one, also Google Cloud Platform. I want to understand the best approach before building everything so i can do it the right way and also, provide the absolute best user experience for watching these videos.

• Creating a smooth animation with ffmpeg filters

  30 mai 2021, par user1503606

  I am trying to add a watermark to a video using ffmpeg and have it animated from left to right in the center of the video.

  


  I have it working with the following command.

  


  ffmpeg -y -i Volkswagen.mp4 -loop 1 -i logo.png -filter_complex overlay=x='W/30*mod(t,30):enable=gt(mod(t,60),0)':y=main_h/2-overlay_h/2:shortest=1 Volkswagen_watermarked.mp4


  


  It works but the outcome looks like this.

  


  https://www.youtube.com/watch?v=M31wG2ub1Lg

  


  The video is from here : https://gist.github.com/jsturgis/3b19447b304616f18657

  


  http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/VolkswagenGTIReview.mp4

  


  As you can see its not very smooth. I am just trying to get my head around the ffmpeg filter functions this is the first time I have used them so would appreciate some advise or is this as good as it gets ?

  


  I have looked at a few other posts but cant find any that can help with this maybe there is another filter I should be using ?

  


  I can run a draw filter command like this and the animation is smoother.

  


  ffmpeg -y -i Volkswagen.mp4 -vf "drawtext=fontfile=/Montserrat-Medium.ttf:text='Text':x=200:y=h-20*t: fontsize=36:fontcolor=yellow@0.9: box=1: boxcolor=black@0.6" -c:a copy VolkswagenText.mp4


  


  But it is obviously not looping.

  


  https://www.youtube.com/watch?v=wdANCWUHaMc

  


  I dont really understand whats happening here.

  


  w*mod(t\,10):enable=gt(mod(t\,60)\,0)

w = width of text
t = time in seconds


  


  I understand if I just have this.

  


  -filter_complex "overlay=x=w*t:y=main_h/2-overlay_h/2:shortest=1"

w*t = every second the x position is incremented by the text width * time


  


  so if the text width is 100px it would be something like this.

  


  1x100 = 100;
2x100 = 200;
etc


  


  What does the mod() function do ? I cant find any help really here https://ffmpeg.org/ffmpeg-filters.html

  


  is this saying when x is greater than the width of the viewport start again ?

  


  enable=gt(mod(t\,60)\,0)


  


  Thanks