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• ffmpeg padding while leaving audio track unchanged

  17 janvier 2016, par mmj

  My cheap 16:9 TV is not able to play correctly a 1280x544 video (I see the 2.35:1 aspect ratio image vertically stretched to 16:9 aspect ratio, incomprehensibly the TV aspect ratio adjustment is disabled if source is USB), so I used ffmpeg (on Windows 10) to add two 88 pixels high horizontal black bars in order to get to a 1280x720 video with a 16:9 aspect ratio, using the following command :

  ffmpeg -i my_input_video.mkv -filter:v "pad=1280:720:0:88" my_output_video.mkv

  My TV play the new video correctly, but it says that the audio is not supported, whereas in the original video it was.

  How can I pad the original video leaving the audio track unchanged ?

• FFmpeg : How to convert horizontal video 16:9 to vertical video 9:16, with blurred background on top and bottom sides

  13 janvier 2016, par gomezo

  I know there is a post to do the contrary :
  FFmpeg : How to convert vertical video with black sides, to video 16:9, with blurred background sides

  but i can’t figure out how to do this with ffmpeg

  here is the input :

  

  and here is the expected result (the background video should be zoomed with the same aspect ratio, cropped to 9/16 and blurred) :

  

  Thanks for your help !

• How to extract time-accurate video segments with ffmpeg ?

  25 mai 2016, par Jim Miller

  This is not a particularly new question area around here, but I’ve tried what’s been suggested there without much luck. So, my story :

  I’ve got a hunk of 15 seconds of straight-from-the-camera.mov video out of which I want to extract a specific chunk, which I can identify by start time and stop time, in seconds. I started by trying to do what I’ll call a "copy extraction" : to get seconds 9 to 12,

  ffmpeg -i test.mov -vcodec copy -acodec copy -ss 9 -to 12 test-copy.mov

  This was a not-bad start, but there are some black frames at the beginning and end of the clip, which I can’t have — it has to be a clean edit from the original. So, I tried recoding the original into a new, trimmed clip :

  ffmpeg -i test.mov -ss 00:00:09 -t 00:00:03 test-out.mov

  This is better, but not quite : There are no longer any black frames at the beginning of the clip, but they’re still there at the end.

  After some more browsing and reading, I then suspected that the problem is that ffmpeg is having trouble finding the proper points because of a lack of keyframes in the original video. So I recoded the original video to (presumably) add keyframes, in a couple of different ways. Since I want to be able to pick video at boundaries of a second ("from 9 seconds to 12 seconds"), I tried, copying various suggestions around the web,

  ffmpeg -i test.mov -force_key_frames "expr:gte(t, n_forced)" test-forced.mp4

  and

  ffmpeg -i test.mov -g 1 test-g-inserted.mp4

  (I built these as mp4’s based on some comments about an mp4 container being needed to support the keyframe search, but I’m honestly just hacking here.) I then tried the extraction as before, but on these new videos that presumably now have keyframes in them. No luck — both seem to be about the same ; the start is OK but there are still black frames at the end. (FWIW, both test-forced.mp4 and test-g-inserted.mp4 also have trailing black frames.)

  So : I’m still stuck, and would like to not be. Any insights out there as to what I’m doing wrong ? I feel like I’m close, but I really need to get rid of those trailing black frames....