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• 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....

• FFMPEG images to video with different frame(image) sizes

  11 mars 2016, par Prem Reddy

  I stumbled upon this problem where ffmpeg video of images passed to it gave me a video of fixed frame sizes.Like stretching lesser sized images or shrinking larger images.But what i want is a video like we get in windows movie maker.With maintaining sizes and if lesser one comes fills black bothsides and displays image as it is.Please answer it ASAP.So,basically different frame sizes.

• FFMPEG drops every odd frame

  28 mars 2016, par Oleksiy Druzhynin

  At running of

  ffmpeg -i /usr/local/Videos/Ads/Samples/DX/DXd_src.ts -vf drawtext=fontfile=/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-R.ttf:text=’%pict_type %pts:hms %pts:raw %eif:n:u’ : fontcolor=white@0.8:fontsize=40:x=7:y=200:box=1:boxcolor=black@0.8 -copyts -muxdelay 0 -muxpreload 0 -copytb 1 -vsync 0 -xerror /usr/local/Videos/Ads/Samples/DX/DXd.ts

  FFMPEG removes every odd frame in for some set of video. I couldn’t understand why ?

  See more on FFMpeg forum