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• Cutting HEVC video results in parts stating with no video (black image) but correct audio for a few seconds

  8 juin 2020, par Oliver

  i have large HEVC video files and want to cut out parts of them. I use ffmpeg for that with the following command :

  



  ffmpeg -i input.mp4 -ss 01:18:47.040 -c:v copy -c:a copy -to 01:18:42.640 output.mp4


  



  i know that there can be problems when copy is used and no re-encoding, that is why i checked before that the frames specified in the -ss and -to parameters where keyframes (i-frames).

  



  So iam expecting to get a clean cut at the beginning and at the end. But what i get is 10 seconds of black image with normal audio in the beginning until the video starts. To make this clear : 10 seconds of video are missing in the beginning but the audio is fine.

  



  Btw : when moving the -ss part before the -i there seem to be no problems with the video (at least in the beginning). I know about the differences of putting -ss before and after the -i, but i also know, that using -ss after the -i should be slower (and was more accurate in the past) but should not make any differences in the final result. That is why I am so irritated.

  


• How to generate a video by looping an image and then concat with another very long video without re-encoding using ffmpeg ?

  23 mars 2021, par Linghao Chen

  I have an image and a very long video (1.5h).
Now I want to generate a heading video about 5 seconds by looping the image, and then concatenate it with the long video. Since the video is long, I don't want to re-encode the videos.
I have tried to generate the heading video using

  


  ffmpeg -loop 1 -i image.png -c:v libx264 -t 5 -pix_fmt yuv420p head.mp4


  


  and then

  


  ffmpeg -f concat -i list.txt -c:v copy concat.mp4


  


  where the list.txt contains

  


  file head.mp4
file longvideo.mp4


  


  I have tried these operations on two machines.
On one machine, the concatenated video has no audio. Moreover, it stucks at 5-10 seconds and directly jump to 11s.
On the other machine, the video and audio are not synchronized.

  


  To provide more information, I have checked the codecs of the two videos by

  


  ffprobe -v error -select_streams v:0 -show_entries stream=codec_name \
  -of default=noprint_wrappers=1:nokey=1 xxxxx.mp4


  


  Both of them are h264.

  


  My question is, how to generate it correctly with ffmpeg ? If it is hard using ffmpeg, is there any method to do it fast ? As far as I know, Adobe Premiere and Final Cut Pro do not export as fast as I expect because they re-encode the videos.

  


• ffmpeg encoded video has video/audio sync delay when uploading to Facebook & WhatsApp

  13 décembre 2019, par royherma

      "fluent-ffmpeg": "^2.1.2",
  
      "ffmpeg": "^0.0.4",
  
      node : 8

  Code to reproduce

  let command = ffmpeg()
  
          .input(tempFilePath)
  
          .input(watermarkFilePath)
  
          .complexFilter([
  
              "[0:v][1:v]overlay=W-w-20:H-h-20"
  
          ])
  
          .videoBitrate(2500)
  
          .videoCodec('libx264')
  
          .audioCodec('aac')
  
          .format('mp4')
  
          .output(targetTempFilePath)

  When applying the ffmpeg encoding command on the attached video, it plays fine on a local device - the issue however is when uploading to Facebook/WhatsApp the audio/video becomes out of sync

  Any ideas on what i need to change in terms of the video/audio settings so that the audio + video are in sync, even when uploaded to the various social networks ?

  Here’s a link to the 3 video files (original, post ffmpeg, post whatsapp upload that includes delay) if you want to get a better idea !

  https://wetransfer.com/downloads/445dfaf0f323a73c56201b818dc0267b20191213052112/24e635

  Thank you and appreciate any help !!