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• How to divide my video horizontally using ffmpeg (without any other side-effects) ?

  1er février 2021, par Mayank Thapliyal

  I am processing my video(640 X 1280 dimensions). I want to divide my video horizontally into 2 separate videos(each video will now be 640 X 640 in dimensions),then combine them horizontally (video dimension will be now 1280 X 640)in a single video. I did the research on the internet and my issue was solved and not solved at the same time

  


  I made a batch file and add these commands in it :-

  


  ffmpeg -i input.mp4 -filter_complex "[0]crop=iw:ih/2:0:0[top];[0]crop=iw:ih/2:0:oh[bottom]" -map "[top]" top.mp4 -map "[bottom]" bottom.mp4
ffmpeg -i top.mp4 -i bottom.mp4 -filter_complex hstack output.mp4


  


  Yes,my task got solved but many other issues also came out of it :-

  


  1.) My output video has NO audio in it. No idea why there is no audio in the end results

  


  2.) My main video file (on which I am doing all this) is 258 MB in size. But the result was only 38 MB in size. No idea what is happening ? And even worse,I closely looked at the video,results were pretty same (only animation were not as smooth in output file as compared to input file)

  


  3.) It is taking too much time(I know that computing takes some time but maybe there may be some way/sacrifice to make the process much quicker)

  


  Thanks in advance for helping me

  


• What is the equivalent of ImageMagick's -liquid-rescale in FFMPEG

  22 février 2024, par Mouaad Abdelghafour AITALI

  I'm interested in the Content-Aware Scale effect. So far, the only way to achieve it is by using ImageMagick (distortion algorithm)

  


  

  


  cmd = f"magick {curFramePath}\

-liquid-rescale {100-DISTORT_PERCENTAGE}x{100-DISTORT_PERCENTAGE}%!\

-resize {videoSize[0]}x{videoSize[1]}\! {resFramePath}"


  


  I would love to achieve comparable results using only FFMPEG.

  


  Thank you for your help

  


• How to generate video as fast as possible with subtitles and audio on node.js + ffmpeg ?

  12 septembre 2018, par DSeregin

  Intro :

  We receive from the site some pieces of text
  Pieces arrive to node.js-server

  At the output we need to get a video, merged from all the pieces of text, voiced by the machine voice, with the added subtitles and audio substrate. So that user could be share this video in the social networks. MKV format doesn`t supported by VK.com

  The options that we have tried :
  1. Get all the text at once, generate the entire speech, create a file with subtitles, burn subtitles in the video .mp4 (vk.com does not support the .mkv container). It took 12 seconds of operations for a 45-second video on the local computer.
  2. Generate audio and video files for each piece of text (with added subtitles). It took one second for one piece of text. At the final request, we merge all pieces together. The last request (merging) took 2-3 seconds, which is already bearable.

  The second variant looks acceptable in terms of speed, but if you run 50 clients at the same time, then the computer (tested on a MacBook PRO 2013, 2.4 GHz i7, 8gb 1600 Mhz DDR3, SSD 256gb) processed only 1 piece from 1 client in 60 seconds (60 times slower), then the computer hung tight.

  • Generation of audio is done through Amazon Polly
  • Generate subtitles via https://github.com/gsantiago/subtitle.js#readme
  • From node.js we call ffmpeg using https://github.com/fluent-ffmpeg/node-fluent-ffmpeg
  • Resolution for video - 1280x720

  The commands we used :

  • Burn video subtitles and trim up to conditional 6 seconds (in the code send unix timestamp)

  ffmpeg -i import / back.mov -i export_0 / tmp.srt -scodec mov_text -t 6 export_0 / output.mov

  • Merging all audio

  ffmpeg -i audio1.mp3 .... -i audio15.mp3 merged.mp3

  • Overlay audio-substrate on the text

  ffmpeg -i merged.mp3 -i back.mp3 -filter_complex amerge -ac 2-c: a libmp3lame -q: a 4 -shortest audio.mp3

  • Merging all videos

  ffmpeg -i video.txt -f concat -c copy video.mp4

  • Overlay audio on video

  ffmpeg -i audio.mp3 -i video.mp4 -i test.mp4 -i export / output.mp3 -c: v copy -c: a aac -map 0: v: 0 -map 1: a: 0 -shortest output .mp4

  Questions that torment :

  1. Is it faster ?

  2. Can I use other codecs or methods of gluing without re-encoding ?

  3. Try to call ffmpeg directly without a wrapper ? (in fact, it gives 50-100 ms of speed)

  4. Try not to save to disk, and write data to Stream and have them glue together in the end ?