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• Batch ffmpeg program

  18 juillet 2017, par Fer

  I would like to learn (do not give the full answer, just hints, please, will give out progress on comments) to program a batch program where, besides adding options given by user input (as in, bitrate, codec to be used, etc) with the tool ffmpeg (which I have installed on C :\Windows\System32) it waits for user input for each of the options ffmpeg has. Example :

  Machine output - Select mp3
  
  User input - Foo.mp3
  
  Machine output - where do you want to begin to cut the mp3?
  
  User input - 00:00:00 (or any other specific time.)
  
  Machine output - We will cut Foo.mp3 at time 00:00:00. When do you want the time to be cut? 
  
  User input - 00:02:10
  
  ...
  
  ...
  
  And so on with all the FFMPEG options.

  How can I exactly do this ? Any hint is appreciated... but do not give the full answer.

• avutil/pixfmt : improve definition of AVColorRange

  18 septembre 2020, par Jan Ekström

  avutil/pixfmt : improve definition of AVColorRange
  As it was brought up that the current documentation leaves things
  
  as specific to YCbCr only, ICtCp and RGB are now mentioned.
  
  Additionally, the specifications on which these definitions of
  
  narrow and full range are defined are mentioned.
  This way, the documentation of AVColorRange should now match how
  
  most people seem to read interpret it at this point, and thus
  
  flagging RGB AVFrames as full range is valid not only according to
  
  common sense, but also the enum definition.
  

  • [DH] libavutil/pixfmt.h

• vframes option ignored in ffmpeg ?

  25 mars 2016, par cooper

  I have a directory that contains 2001 PNG files. I can convert all of the frames to an mp4 video using ffmpeg and the following command :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -c:v libx264 -r 30 \
  
  -pix_fmt yuv420p input1ia.mp4

  This works fine. However, I am creating a more complicated application that needs to read only the first 1020 files in the directory (specifically 0 thru 1019). Some googling around led me to the -vframes option. My problem is — it seems to get ignored or at least interpreted differently than I expect.

  My modified command looks like :

  ffmpeg -framerate 60 -start_number 0 \
  
  -i pic.comp2.%07d.png -vframes 1020 -c:v libx264 
  
  -r 30 -pix_fmt yuv420p input1.mp4

  It seems like many other people doing the same thing as me do not encounter this issue. So I did some more digging. I tried changing vframes from 1020 to -vframes 20, and this seemed to work properly. So now I am thinking it might be some kind of mismatch between -framerate and -r ?

  The full resultant video is 33 sec long... which makes sense mathematically.

   1 sec
  
   ---------   x  2001 frames = 33.35 seconds
  
   60 frames

  That’s why I thought that specifying 1/2 of the PNGs as the ’end point’ would result in a video of the first 16-17 seconds. But I always get the full length video from using the -vframes option.

  I assume my input to -vframes must be incorrect mathematically, since a small number of frames seems to work. However, I do not understand why.

  The most educated guess I can seem to make is that it is reading the PNGs as 60fps (-framerate), but the -r makes the output video 30fps or something ? However, then I would assume that the full output video would not be 33 seconds long.