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• FFMPEG detect color bars and tone in video

  23 novembre 2016, par Chris Harvey

  I am trying to detect if a video has any valid content or is just the standard broadcasting bars & tone. So far I’ve looked at this question : http://superuser.com/questions/1036449/detect-color-bars-ffmpeg/1036478#1036478
  which generates bars & tone from the first frame and then compares that against the rest of the stream but in my case I need to run the ffmpeg command within a folder that only has one file that has already been found by my python script.

  Is it possible to use ffmpeg’s blend=difference to check that a short bars & tone clip is a subclip of one of my video files ? I’m thinking of this in the same way you can check if a string is within a string, or is there a better way to check for bars that I’m not thinking of ?

  Thanks !

• Video to image sequence export (preserving color range)

  20 août 2017, par Floating Point

  When I convert the material which is in legal range (tv) to prores, legal range is preserved, but when I export it to image sequence (tiff), I get files which are already in full range, although I try to preserver the original values with -vf "zscale=rin=limited:r=limited".

  Is ffmpeg automatically changes color range when exporting to images ?

• H264 to MP4 with Bframe play back and forth on google chrome[ffmpeg]

  2 mai 2017, par Ravi Agola

  I want to generate a mp4 container with h264 encoded file.

  H264 file contains [I P B B][P B B][P B B][P B B] frames.

  when I generate a mp4 file with FFmpeg, It works well with FFplay as well as VLC but on google-chrome mp4 file plays frame back and forth.

  ffmpeg -i input.h264 -vcodec copy output.mp4

  when i use internal codec library(libx264) it works well on (ffplay,vlc and google-chrome)

  ffmpeg -i input.h264 -vcodec h264 output.mp4

  as above command transcode h264(native) to h264(x264), I don’t want to transcode file as I will be using it with ffmpeg library.

  when I use h264 without B frame it works well in both cases.

  I have tried some experiment with sample test file available here.

  direct conversion(MKV to MP4) works well with chrome as below

  ffmpeg -i jellyfish-3-mbps-hd-h264.mkv -vcodec copy output.mp4

  (MKV to H264 and H264 to MP4) plays back and forth on chrome

  ffmpeg -i jellyfish-3-mbps-hd-h264.mkv -vcodec copy output.h264
  ffmpeg -i output.h264 -vcodec copy output.mp4

  I get message in this case
  [mp4 @ 0xb6f8b20] Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly
  [mp4 @ 0xb6f8b20] pts has no value"

  what can be a reason behind this behavior ?

  Thanks.