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• ffmpeg - invalid duration

  22 septembre 2016, par OmidAntiLong

  For a project I’m working on I have a small bash script that loops over an input csv file of timecodes, and uses ffmpeg to create screenshots of a given film at each timecode. The csv file is in the format hh:mm:ss,id - it looks like this (extract)

  00:00:08,1
  
  00:00:49,2
  
  00:01:30,3
  
  00:02:38,4
  
  00:03:46,5
  
  00:04:08,6
  
  00:04:26,7
  
  00:04:37,8
  
  00:04:49,9
  
  00:05:29,10
  
  00:05:52,11
  
  00:06:00,12
  
  00:06:44,13
  
  00:07:49,14
  
  00:08:32,15
  
  00:09:28,16
  
  00:10:17,17
  
  00:10:44,18
  
  00:11:48,19
  
  00:12:07,20

  I’ve used it without issue in the past, but today I’ve come to update some of the films and I’m getting a weird issue where ffmpeg is complaining that my input timecode is invalid, despite being in the right format.

  The new input csv files are the same format as the old ones, but it seems like every so often ffmpeg drops the hours from the hh:mm:ss timestamp. If I comment out the ffmpeg line, everything prints to the terminal as expected (but obviously I get no screenshots).

  This is my loop code :

  while read code a
  
  do
  
    echo $code
  
    f="$(printf "%03d" $i)"
  
  
  
    ffmpeg -loglevel error -y -ss $code -i $FILM -vframes 1 -q:v 2 $OUTPUT/$f.jpg
  
  
  
    ((i++))
  
  done < $INPUT

  I’ve tried all sorts, including padding the csv with extra 0s - which works until the hours tick over to 01.

  

  Does anyone have any ideas ? I’m scratching my head.

  Cheers

• Convert Transparent PNGs to a Transparent Video

  15 février 2023, par Aurora7979

  I have a set of transparent PNG pictures, and I want to convert them into a video with transparent background (play the PNGs continuously).

  


  First, I used ffmpeg with the terminal command :

  


  ffmpeg -framerate 30 -pattern_type glob -i '*.png' \-c:v libx264 -pix_fmt yuva420p out.mp4


  


  And I learnt that the codec libx264 does not compatible with the alpha channel. Then, I changed to another codec and used the following command :

  


  ffmpeg -framerate 30 -pattern_type glob -i '*.png' \-c:v libvpx-vp9 -pix_fmt yuva420p out.mp4


  


  However, QuickTime Player cannot play the resulting out.mp4. I don't know if it was because the video conversion failed or it was the fault of QuickTime Player. The terminal didn't show any error message, though.

  


  Therefore, I would like to ask :

  


  


  1. Which codec I should use to create a transparent video that a normal video player can play ?

     


  


  2. Can the output MP4 video format support transparent videos ?

     


  


  3. If there is another tool that is far more superior than ffmpeg for my purpose, I am willing to give it a try.

     


  


  


  Thank you for any advice.

  


  All the best,

  


  Aurora

  


• matplotlib "RuntimeError : No MovieWriters available" when ffmpeg is installed

  11 août 2014, par user1637894

  I’m using OSX Mavericks and the Enthought Canopy distribution of python. I’m trying to run any simple example script that uses matplotlib.animation to save an animation, but I always get the following error :

  Traceback (most recent call last):
  
  File "/Users/Sam/Google Drive/Spyder workspace/MiscScripts/animation.py", line 14, in <module>
  
      FFMpegWriter = manimation.writers['ffmpeg']
  
  File "/Users/Sam/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/matplotlib/animation.py", line 63, in __getitem__
  
      raise RuntimeError("No MovieWriters available!")
  
  RuntimeError: No MovieWriters available!
  
  </module>

  Ffmpeg is installed on my system : I can access it by typing ffmpeg into a new terminal. So I’m guessing matplotlib simply doesn’t know that ffmpeg is available because it is not in the python path. So I tried typing which ffmpeg into a new terminal window to find where ffmpeg was installed, then I added this string to my python path via sys.append('path_here'), but this didn’t help.