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• Merging 2 videos with overlay causes async problems

  3 novembre 2014, par Gnagy

  I’m using following FFMPEG command to merge 2 MKV inputs with the overlay parameter.
  The result should be one output with input1 on top of input2.
  In the process, the output should be webm.
  Both inputs are of the same length (with a margin of a second).

  ffmpeg -i input1.mkv -i input2.mkv -y -filter_complex [0:v]select=1, setpts=PTS-STARTPTS, scale=400:300, pad=400:600 [top]; [1:v]select=1, setpts=PTS-STARTPTS, scale=400:300 [bottom]; [top][bottom] overlay=0:300 [out]; [0:a:0][1:a:0] amerge=inputs=2 [a]; [a] asetpts=PTS-STARTPTS [a] -map [a] -c:v libvpx -crf 10 -b:v 360K -q:v 7 -c:a libvorbis -b:a 32k -map [out] output.webm

  This command does what it’s supposed to do.

  However, the 2 videos are not totally in sync.

  The input1 on the top plays decently while the input2 on the bottom has black frames, slows down or speeds up and causes the audio and video to be out of sync.

  To rule out the individual quality of the inputs, we switched the position of the videos and the top video always plays decently.

  How can we fix this ?

• FFMPEG - speed up/slow down video, add jitter etc

  27 septembre 2019, par Darrell

  I’m trying to put together a Windows script that will process short videos in a folder.
  The videos will be shot at a high frame rate 60+ fps and be about 4-5 secs long.

  Basically I am looking to make various style clips, using fast/slow effects, back and forth etc.
  So, the script might process a video, make it start normal speed, then slow motion. Next video might be normal speed, slomo, normal speed slomo. Next video might be forwards,back, forwards back, slomo.

  See example : (this is a compliation, I’m looking at processing individual videos in a folder.)

  http://www.youtube.com/watch?v=K03IBQZu8SQ

  I’m guessing there is no way to do this, other than splitting a clip using FFMPEG, processing the bits, then merging back together ? I can’t seem to find a way to do it as one clip.

• Extract specific frames of youtube video without downloading video

  22 janvier 2023, par Kashish Arora

  I need to extract specific frames of an online video to work on an algorithm but I don't want to download the whole video because that would make it highly inefficient.

  


  For starters, I tried working with youtube videos. I can download whole of the video using youtube-dl in this way :

  


  ydl_opts = {'outtmpl': r'OUTPUT_DIRECTORY_HERE',}
with youtube_dl.YoutubeDL(ydl_opts) as ydl:
    ydl.download([url])


  


  And then I can capture individual frames.

  


  I need to avoid downloading the whole video. After some research, I have found that ffmpeg might help me do this. I found no way to download just the frames so if this is not possible, the second option is that I can download specific portions of the video. One such example in linux is here but I couldn't find any solution for python.

  


  What is a good way to download just the frames, or portions of videos (in python) without downloading the entire thing ?