Sur d’autres sites (5471)

• How to read a video stream(H.264) bitrate via ffprobe if the video is VBR

  26 janvier 2021, par Sean
  

  1. if the video stream is VBR, which means the bitrate is variable, so how to read the bitrate via ffprobe ?

  


  2. How to get know the video stream is CBR or VBR ?

  


  


• How to replace a snippet in a video without reencoding the whole video

  3 novembre 2022, par Simon Streicher

  I am trying to edit and replace a section of a video without reencoding the whole video.
Here are the steps I think I need to take :

  


  1. Find keyframes

  


  input :

  


  ffprobe -v error -select_streams v:0 -skip_frame nokey -show_entries frame=pkt_pts_time -of csv=p=0 'example.mkv'


  


  output :

  


  0.000000
1.001000
11.011000
13.430000
20.812000
30.822000
40.832000
50.842000
⋮


  


  2. Export relevant section

  


  For example, export the snippet 40.832000 → 50.842000.

  


  3. Edit and reencode

  


  After editing that section, I need to reencode it to the original codecs for compatibility with the surrounding video. For example, this is the original codecs :

  


  Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x1600 [SAR 1:1 DAR 12:5], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc (default)


  


  4. Inject edit back into the video stream

  


  Finally, I need to use FFmpeg somehow to retain everything from the original file (audio, subtitles, chapters, etc.) and to construct a new video stream (for example, Stream #0:0) that is exactly 0 → 40.832000 of the original, the whole edited section, and 50.842000 → end of the original section.

  


  My main questions are :

  


  

  • A. How do I trim the video stream in 2. without reencoding ?

  


  • B. Assuming that the edited video's resolution will remain the same, what is the command for FFmpeg to encode my edit to the codecs in 3. (and would the video be concatenable with the original video) ?

  


  • C. How should I go about glueing the sections together ? Should I simply trim Stream #0:0 into sections v1 = 0 → 40.832 and v2 = 50.842 → end and then concatenate a new stream as new = v1 + edited + v2 ?

  


  • D. How do I replace Stream #0:0 with new ?

  


  


  And probably the most important question : are my assumptions correct and can this be achieved ?

  


• Vertical video play does not sync with multiple stacked video

  5 novembre 2018, par Sabha

  I dont know if I have wrote the subject well and if that can be understood. Nevertheless, here is an explanation

  I have 7 videos of different dimensions where the width is same (1080). I wish to place them one below the other to get a full hd vertical video (1080x1920). I tried the -filter_complex vstack filter in ffmpeg and got all the videos aligned one below the other and I am getting a perfect 1080x1920 full hd vertical video but they dont sync with each other. Once the videos are in sync, I need to put an audio too which should also sync with the in-sync video that will be made.

  There is so much of complexity. Please advice how do I make them sync. Is there any software that can allow me to put 7 videos one below the other in a timeline ? (if not 7, atleast 3-4 videos). Please advice where and how to start.

  Is there any option in Adobe Premier or any other software ?

  Thanks

  EDIT : I am doing a very long procedure to combine all 7 videos vertically

  first i use

  ffmpeg -i video1.mp4 -i video2.mp4 -preset veryslow -filter_complex vstack video12.mp4

  and then

  ffmpeg -i video12.mp4 -i video3.mp4 -preset veryslow -filter_complex vstack video123.mp4

  so on and so forth

  Is there a better way to do it all in one command ?