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• lavc/qtrle : Use AV_PIX_FMT_PAL8 for 1-bit video

  29 décembre 2015, par Mats Peterson

  lavc/qtrle : Use AV_PIX_FMT_PAL8 for 1-bit video
  This commit fixes the lack of palettized display of 1-bit video
  
  in the qtrle decoder. It is related to my commit of
  
  lavf/qtpalette, which added 1-bit video to the "palettized video"
  
  category. As far as I can see, everything works fine, but comments are
  
  of course welcome.
  Below are links to sample files, which should now be displayed properly
  
  with bluish colors, but which were previously displayed in black &
  
  white.
  Matroska :
  
  https://drive.google.com/open?id=0B3_pEBoLs0faNjI0cHBMWDhYY2c
  
  Earth Spin 1-bit qtrle.mkv
  QuickTime (mov) :
  
  https://drive.google.com/open?id=0B3_pEBoLs0faUlItWm9KaGJSTEE
  
  Earth Spin 1-bit qtrle.mov
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/qtrle.c
  • [DH] tests/ref/fate/qtrle-1bit

• lavf/qtpalette : Ignore greyscale bit in certain cases

  2 janvier 2016, par Mats Peterson

  lavf/qtpalette : Ignore greyscale bit in certain cases
  The QuickTime File Format Specification states the following :
  "Depth : A 16-bit integer that indicates the pixel depth of the
  
  compressed image. Values of 1, 2, 4, 8 ,16, 24, and 32 indicate the
  
  depth of color images. The value 32 should be used only if the image
  
  contains an alpha channel. Values of 34, 36, and 40 indicate 2-, 4-, and
  
  8-bit grayscale, respectively, for grayscale images."
  There is no mention of value 33, i.e. 1-bit video (0x01) with the
  
  greyscale bit (0x20) set. I therefore suggest that we ignore the
  
  greyscale bit when processing 1-bit video. Another reason to do this is
  
  that the first 1-bit sample file below will be displayed properly with
  
  blue colors in QuickTime in Windows or Mac *in spite of* the greyscale
  
  bit being set.
  Also, QuickTime in Windows or Mac ignores the greyscale bit if the
  
  video sample description contains a palette, regardless of bit depth.
  
  This is undocumented behaviour, but I think we should do the same, and
  
  it seems pretty logical after all, since one wouldn’t really bother
  
  putting a customized palette into a grayscale file anyway. See the
  
  second 8-bit sample file below, which has the greyscale bit set, and
  
  which contains a palette in the video sample description. In Windows or
  
  Mac, it will be displayed with the palette in the sample description, in
  
  spite of the greyscale bit being set.
  Sample file 1 (1-bit QuickTime Animation) :
  
  https://drive.google.com/open?id=0B3_pEBoLs0faTThSek1EeXQ0ZHM
  
  Earth Spin 1-bit qtrle orig.mov
  Sample file 2 (8-bit QuickTime Animation) :
  
  https://drive.google.com/open?id=0B3_pEBoLs0fad2s0V1YzUWo5aDA
  
  quiz-palette+gs.mov
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/qtpalette.c

• Why ffmpeg take lot of data while extracting frames from a online video ?

  28 juillet 2023, par strcurious

  I just extracted frames from a online video , it extracted around 956 frames. Size of all the extracted frames is 28.6 mb on hard drive but it just consume around 400-500 mb data. I extracted 1 frame every 3 second

  


  here is the command

  


  ffmpeg -ss 00:02:45.000 -i 'example.com/1mp4' -t 45:02.000 -vf fps=1/3 %01d.jpeg


  


  Is there any way I can see frames of a video online whenever I hover pointer on duration of video ?

  


  I expected to consume it's less data