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• How do I reverse a video in ffmpeg ?

  19 avril 2023, par Will Beeson

  - Full Error :

  


  Stream specifier 's1:v' in filtergraph description [0]split=2:outputs=2[s0][s1] ;[s1:v]reverse[s2] ;[s0][s2]concat=a=0:n=2:v=1[s3] matches no streams.

  


  - Formatted Error

  


  

  • [0]split=2:outputs=2[s0][s1] ;

  


  • [s1:v]reverse[s2] ;

  


  • [s0][s2]concat=a=0:n=2:v=1[s3]

  


  


  - Code :

  


  instances = (
    ffmpeg
    .input(self.video_file)
    .filter_multi_output(filter_name="split", outputs=2)
)
ordered_edits = []
for i in range(2):
    if i%2 == 0:
        ordered_edits.append(
            instances[i]
        )
    else:
        ordered_edits.append(
            instances[i].video.filter(filter_name="reverse")
        )
(
    ffmpeg
    .concat(*ordered_edits, a=0, v=1)
    .output('done/output.mp4')
    .run(overwrite_output=True))


  


  Looking at the error code, it seems like s1:v should be a valid reference. The only thing I can think of is that there is an issue saving an exclusive video input into a nonspecified output. The files don't actually have any audio, I just want the video.

  


  I'm lost, please help ffmpeg experts of the world !

  


• How can I download a video with url beginning with blob:https://…

  11 août 2017, par iMax

  I would like to know if it is possible to download a video from a URL beginning with blob :

  blob:https://www.xyz123…

  i would prefer a terminal solution (ffmpeg ?, youtube-dl ?). but i have not found anything on the world wide web.

  Again : I have the url of the video stream, which looks like the above. How can I download the complete video ?

  Update

  Ok. I now found a webpage which allowed me to download the video file I wanted :
  https://video-download.online/

  But I am still wondering if there is a Terminal solution for downloading video with blob-URL (like in arte mediathek [ example arte ] or in zdf mediathek [ example zdf ]).

  Does nobody know how to do it ?

• ffmpeg : Dynamically set output duration based on sliding text width

  18 janvier 2016, par John Whiteman

  I need to create a smooth ’news ticker’ on a low powered android device. Unfortunately this is impossible at runtime using HTML or native code as there is always some stutter or glitch.

  I’ve created a solution that gives me a smooth result by encoding an mp4 for each message and displaying one video after the other. This is the code I’m using :

  ffmpeg -f lavfi -i color=c=black:s=1280x100 -vf "drawtext=BebasNeue.otf:fontsize=60:fontcolor=white:y=h-line_h-30:x=-(4*n)+1280:text='Hello world'" -t 10 output.mp4

  Problem :
  I need to set the video’s duration dynamically so that the video stops when the text has completed it’s journey from right to left. The messages will be of varying lengths and I need each message to scroll at a constant speed (ie. an mp4 with a longer message would have a longer duration).

  Is this possible via an expression ? If not is there some clever way I can calculate this outside of ffmpeg and pass it to the ’-t’ (duration) parameter ?

  ** Edit **
  To calculate outside of ffmpeg I can do a calculation like video_width + text_width / video_fps (ie. 1280 + 262 / 25) to give me the duration. So now I’m just looking to see if this is possible within the ffmpeg command line itself. t

  Many thanks