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• Révision 20018 : Quand le logo n’est pas editable, et qu’il n’y a ni logo normal ni logo survol d...

  20 novembre 2012, par cedric -

• How to flatten a VR video to display in normal screen ? [closed]

  14 mai 2023, par d-b

  I am not sure about the terminology here, but I have a VR-video that is intended to be shown using a headset with separate screens for each eye. It is not 3D in the sense that when you turn your head you will see something different, it is just "2,5D" so you get a sense of depth when looking at it. There are two video channels that are more or less identical, they are just recorded with slightly different angle, similar to how human eyes see the world. I hope this makes it clear what type of video I have, otherwise please ask for clarification in a comment (and if there is a special terminology for this type of video, please let me know).

  


  More details : the original video is 4320x2160, basically 2 square channels at 2160 x 2160.

  


  I want to show this video undistorted on a regular screen.

  


  I have read the following questions here on SO :

  


  


  1. How to reproject and join these two clips with ffmpeg ?

     


  


  2. Flatten 360 fisheye video

     


  


  3. How to de-warp 180 degree or 360 degree fisheye video with ffmpeg ?

     


  


  4. Flatten 360 fisheye video

     


  


  5. Unwarping 180 VR Footage with FFmpeg v360 Filter

     


  


  


  (and problably a few more).

  


  I think I want to extract the two video channels (note that they are in the same video stream, not like in a movie where you can have several separate audio streams for different languages) into separate files and then "undistort" them.

  


  (3) gave me a command to splitting the video into two files :

  


  ffmpeg -i -myclip.mp4 -filter_complex "[0]crop=iw/2:ih:0:0[left];[0]crop=iw/2:ih:ow:0[right]" -map "[left]" -map 0:a /tmp/left.mp4 -map "[right]" -map 0:a /tmp/right.mp4


  


  That seemed to have worked as expected but then I also need to "undistort" the content because it was filmed with some fisheye lens or something like that (straight lines not in the absolute centre of the image are more or less circular).

  


  (5) suggested this command :

  


  ffmpeg -i left.mp4 -vf "v360=input=hequirect:output=flat:h_fov=100:v_fov=67.5:w=1280:h=720" leftfixed.mp4


  


  but that produced an output that was 4320x2160 (obviously only from one channel, since input was just one channel) but just the centre of the original image, I estimate the content to be the 500x250 px (upscaled to 4320x2160, so very blocky) of the midpoint of the original image.

  


  How can I "undistort" this video so it looks good on a 2D-screen while the size is preserved ?

  


• Revision 8fb6c58191 : Implement sse2 and ssse3 versions for all sub_pixel_variance sizes. Overall spe

  20 juin 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /test/variance_test.cc

  
   Modify /vp9/common/vp9_rtcd_defs.sh

  
   Add /vp9/encoder/x86/vp9_subpel_variance.asm

  
   Modify /vp9/encoder/x86/vp9_subpel_variance_impl_sse2.asm

  
   Modify /vp9/encoder/x86/vp9_variance_impl_mmx.asm

  
   Modify /vp9/encoder/x86/vp9_variance_impl_sse2.asm

  
   Delete /vp9/encoder/x86/vp9_variance_impl_ssse3.asm

  
   Modify /vp9/encoder/x86/vp9_variance_mmx.c

  
   Modify /vp9/encoder/x86/vp9_variance_sse2.c

  
   Delete /vp9/encoder/x86/vp9_variance_ssse3.c

  
   Modify /vp9/vp9cx.mk

  
  
  Implement sse2 and ssse3 versions for all sub_pixel_variance sizes.

  Overall speedup around 5% (bus @ 1500kbps first 50 frames 4min10 ->
  3min58). Specific changes to timings for each function compared to
  original assembly-optimized versions (or just new version timings if
  no previous assembly-optimized version was available) :

  sse2 4x4 : 99 -> 82 cycles
  sse2 4x8 : 128 cycles
  sse2 8x4 : 121 cycles
  sse2 8x8 : 149 -> 129 cycles
  sse2 8x16 : 235 -> 245 cycles (?)
  sse2 16x8 : 269 -> 203 cycles
  sse2 16x16 : 441 -> 349 cycles
  sse2 16x32 : 641 cycles
  sse2 32x16 : 643 cycles
  sse2 32x32 : 1733 -> 1154 cycles
  sse2 32x64 : 2247 cycles
  sse2 64x32 : 2323 cycles
  sse2 64x64 : 6984 -> 4442 cycles

  ssse3 4x4 : 100 cycles (?)
  ssse3 4x8 : 103 cycles
  ssse3 8x4 : 71 cycles
  ssse3 8x8 : 147 cycles
  ssse3 8x16 : 158 cycles
  ssse3 16x8 : 188 -> 162 cycles
  ssse3 16x16 : 316 -> 273 cycles
  ssse3 16x32 : 535 cycles
  ssse3 32x16 : 564 cycles
  ssse3 32x32 : 973 cycles
  ssse3 32x64 : 1930 cycles
  ssse3 64x32 : 1922 cycles
  ssse3 64x64 : 3760 cycles

  Change-Id : I81ff6fe51daf35a40d19785167004664d7e0c59d