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• batch file for encoding videos with ffmpeg - "variable" : %%a

  8 juin 2015, par labrat

  what is the meaning of ’%%a’ and ’%% na’ in this expression : http://www.pasteall.org/58875 ?

  for %%a in ("*.*") do ffmpeg -i "%%a" "newfiles\%%~na.mp4"pause

  I want to batch encode a couple of video files. all are in the same folder with nothing else in it. I found explanations which tell that it is a variable. but for what does a variable like this stand ?

  working on win 7 ult 64bit.

• ffmpeg through python subprocess fails to find camera

  27 juillet 2021, par Ofer Sadan

  Weird problem here, i use this command to capture my webcam through ffmpeg (through cmd on windows) :

  



  ffmpeg -y -t 300 -rtbufsize 1024M -f dshow -i video="Lenovo EasyCamera" -c:v libx264 -preset veryslow -crf 25 Desktop.mkv


  



  and everything works fine. But when i try the very same command through python as a subprocess it fails. Here's the python code :

  



  from subprocess import Popen
cmd = ['ffmpeg', '-y', '-t', '300', '-rtbufsize', '1024M', '-f', 'dshow', '-i', 'video="Lenovo EasyCamera"', '-c:v', 'libx264', '-preset', 'veryslow', '-crf', '25', 'Desktop.mkv']
p = Popen(cmd)


  



  Outputs the following error and freezes :

  



  [dshow @ 00000000023a2cc0] Could not find video device with name ["Lenovo EasyCamera"] among source devices of type video.
video="Lenovo EasyCamera": I/O error


  



  Can anyone figure this out and tell me what i'm doing wrong ? Or is it some known bug in python or the subprocess module (using python 3.6.1, but not attached to the specific version if it will help me solve this problem) ?

  



  Thanks in advance !

  



  P.S. This question is a follow up to this one, if that's relevant : How to grab laptop webcam video with ffmpeg in windows

  


• Large Panorama to Panning Video in FFMPEG

  7 octobre 2018, par Sogree

  I have been looking for a command line based solution for panning panorama’s like this : Large Panorama to Panning Video Based on that answer I’ve been experimenting with switches and formulas but they are a bit too complex for me (even after reading the ffmpeg command line help functions). What I would like to do :

  Pan an image from left to right. The input file is an PSD that has a large resolution (for example 3350x13140 pixels) but this is variable. So I would like ffmpeg to :

  1) Resize/scale the image to a set height of 1080 (so the height is set, but the width is flexible for the Pan) (is this step needed ??)

  2) Crop (and loop=1) the image to 1920x1080 (for me, combining scale and crop gives an error)

  3) But before starting the pan I would like it to wait for 2 seconds (so the most left part of the image would stand still for 2 seconds before panning)

  4) And after finishing the pan I would like it to wait for 2 seconds again (so the most right part of the image would stand still for 2 seconds before panning)

  5) Panning speed : Based on the width of the image (in this case 13140 pixels) I would like the panning speed to be 3,5 seconds per 1000 pixels. So in this case 46 seconds for the pan (and the end result (video length) would be 50 seconds (2 + 46 + 2).

  Only bullet 2 (with 1) I seem to be able to do.

  ffmpeg -loop 1 -framerate 60 -i in.psd -vf crop=1920:ih :’min((iw/10)*t,9*iw/10)’:0 -t 20 -c:v out.mp4

  So how should I alter the above options ? And in another posting this was listed :

  ffmpeg -loop 1 -r 60 -i in.psd -vf crop=1920:1080:n:0 -frames:v 11220 -pix_fmt yuv420p -preset fast -crf 25 out.mkv

  https://www.reddit.com/r/ffmpeg/comments/9051f1/i_want_to_pan_across_an_image_from_left_to_right/e2ukaah/

  But that command does not rescale the image (only pans the top (1920x1080) of the image).

  Maybe I need a combination of the two ? Or is using the zoompan command (with zoom set to off ?) a better option ?