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• FFMPEG : Reversing only a segment of a video file

  25 juillet 2019, par N. Johnson

  I am writing a script that takes a piece of video and then reverses the same piece of video and then concats the two together so the final video plays forwards and then loops backwards. I should note that eventually I want to be able to pull an unequal length for the reverse part.

  I can get the entire file to do this, but getting just a segment is not working as expected.

  See code below

  I’ve tried :

  %1 = timecode to seek to (the video file is only 20 seconds and never any longer)

  %2 = length of segment to pull out

  %3 = usually the same as %2 but may be different if we want to only reverse 2 seconds instead of the full 5 for example.

  ffmpeg -ss 00:00:%1 -an -i test.mp4 -t 00:00:%2 out.mp4
  
  :: the above works as expected
  
  
  
  :: this doesn't, no matter what I put into -ss. I've also tried moving -ss out front of the -i as suggested in the documentation? It gives me the right length of segment but never starts in the right place. 
  
  
  
  ffmpeg  -an -i test.mp4 -ss 00:00:xx -t 00:00:%3 -vf reverse reversed2.mp4
  
  
  
  :the below works fine
  
  ffmpeg -f concat -safe 0 -i mylist.txt -c copy output.mp4

  When I run this with say %1 = 05 and %2 = 05, I get a segment from 5 seconds in that lasts 5 seconds. Then I get a seemingly random starting point and 5 seconds of reversed video. I’ve tried a number of inputs in "XX" from 10 (which I think is right) to 0 to 19 and all of them produce output. But it’s all wrong.

• ffmpeg itsoffset doesnt apply offset to mp4

  26 juillet 2019, par brux

  The following command mixes an mp4 and an mp3 together, keeping the audio from the mp4.

  ffmpeg -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  The command works as expected.

  Now I want to offset the mp4 file (both the audio and video stream of the mp4) so that there is a delay of 500ms at the start of the mp4, here is my command :

  ffmpeg -itsoffset 00:00:00.500 -i video.mp4 -i audio.mp3 -map 0:v -c:v copy -filter_complex '[0:a][1:a]amix[aout]' -map '[aout]' -shortest out.mp4

  This doesnt work as expected, the output doesnt have the expected delay of 500ms at the start of the mp4 streams. It appears the output is just the same as the first command I ran.

  The version of ffmpeg I am using is :

  ffmpeg version n4.0-39-gda39990

  Here are the files I’m using :

  video.mp4

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/storage/emulated/0/video.mp4':
  
        Metadata:
  
          major_brand     : mp42
  
          minor_version   : 0
  
          compatible_brands: isommp42
  
          creation_time   : 2019-07-26T03:28:49.000000Z
  
          com.android.version: 8.0.0
  
        Duration: 00:00:07.64, start: 0.000000, bitrate: 20534 kb/s
  
          Stream #0:0(eng): Video: h264 (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1920x1080, 20966 kb/s, SAR 1:1 DAR 16:9, 29.70 fps, 29.75 tbr, 90k tbn, 180k tbc (default)
  
          Metadata:
  
            rotate          : 270
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : VideoHandle
  
          Side data:
  
            displaymatrix: rotation of 90.00 degrees
  
          Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
          Metadata:
  
            creation_time   : 2019-07-26T03:28:49.000000Z
  
            handler_name    : SoundHandle

  audio.mp3

  Input #0, mp3, from '/storage/emulated/0/audio.mp3':
  
        Metadata:
  
          album           : Sunflower (Spider-Man: Into the Spider-Verse) - Single
  
          composer        : Louis Bell, Carter Lang, Austin Richard Post, Billy Walsh & Khalif Malik Ibin Shaman Brown
  
          genre           : Hip-Hop/Rap
  
          copyright       : This Compilation ℗ 2018 Republic Records, a division of UMG Recordings, Inc.
  
          title           : Sunflower (Spider-Man: Into the Spider-Verse)
  
          artist          : Post Malone & Swae Lee
  
          album_artist    : Post Malone & Swae Lee
  
          track           : 01/01
  
          TYER            : 2018-10-18T07:00:00Z
  
        Duration: 00:02:38.07, start: 0.000000, bitrate: 325 kb/s
  
          Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 320 kb/s
  
          Stream #0:1: Video: mjpeg, yuvj444p(pc, bt470bg/unknown/unknown), 1400x1400 [SAR 300:300 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
  
          Metadata:
  
            comment         : Cover (front)

• ffmpeg image + audio to video [ERROR width not divisible by 2 (2001x2048)]

  30 août 2019, par Martin

  I am trying to use ffmpeg to take an audio file, image, and render a video. I need to encode this video correctly to be able to upload to YouTube, but am running into an error saying :

  [libx264 @ 0x7fffbc28a380] width not divisible by 2 (2001x2048) 
  
  Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  I get this error after using the following command to render the video :

  $ ffmpeg -loop 1 -framerate 2 -i 'front.jpg' -i 'output.mp3' -c:v libx264 -preset medium -tune stillimage -crf 18 -c:a copy -shortest -pix_fmt yuv420p outputReEncoded.mkv

  The image is a square, so I wan’t my output video file to not stretch the image, and just have the square image ontop of a black background. I’m having trouble using scale to fix the width, can anyone help me fix my ffmpeg statement so that my video will correctly render, and be uploadable to YouTube ? Thx