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• Size of files was increased after splitting by Ffmpeg

  29 avril 2014, par user3584205

  I use this code to split file to multiple parts :

  @echo off
  
  for %%i in (*.mp4) do ( 
  
    ffmpeg -i "%%~i" -vcodec copy -acodec copy -ss 00:00:00 -t 00:00:05 "D:\Ebook\%%~ni_1.mp4"
  
    ffmpeg -i "%%~i" -vcodec copy -acodec copy -ss 00:00:05 -t 00:00:10 "D:\Ebook\%%~ni_2.mp4"
  
    ffmpeg -i "%%~i" -vcodec copy -acodec copy -ss 00:00:10 "D:\Ebook\%%~ni_3.mp4"
  
    )
  
  pause

  It worked but I have a problem. It is total size of parts is larger than original file.

  Original : 700 MB and after splitting :

  Part 1: 225
  
  Part 1: 500
  
  Part 2: 250

  Why ? And how to keep same quality and size of files after splitting ? Thank you very much !

• YUV420p to other formats, color shift problems

  1er juin 2013, par Sam

  So I'm writing a color detection application using an AR Drone. The drone sends my python/opencv socket server an image from its camera in YUV420p format.

  What I do to access the image as an opencv IPLImage is the following (and yes this is inefficient but I didn't / don't want to have to write new conversion tools myself) :

  1. Save the yuv image to a file (some_image.yuv)
  2. subprocess.call(insert ffmpeg call here)
  3. Read the resultant file (bmp, png, it doesn't matter) back in using cv.LoadImage

  My problem right now is a very noticable color shift. I'm waving a red felt sheet in these pictures. The first one shows a heavy yellow tint. The second isn't as bad but is very rare — mostly when I have the red sheet it's heavily tinted.

  • Tinted image : http://i.stack.imgur.com/BQikM.png
  • Less-tinted image : http://i.stack.imgur.com/ezHyy.png

  I'm wondering both of these things :

  1. if there's either a better way to do this
  2. If the color tinting issue can be resolved

  My ffmpeg conversion line looks something like

  ffmpeg -s 640x480 -vcodec rawvideo -f rawvideo -pix_fmt yuv420p -i image.yuv -vcodec bmp -f image2 output.bmp

  I've also tried :

  ffmpeg -f rawvideo -s 640x480 -pix_fmt yuv420p -vf colormatrix=bt709:bt601 -i image.yuv -f image -vcodec png output.png

  The color shift is always there, unfortunately !

  The color shift is my big problem right now as I later convert the image to HSV and use thresholding to choose a color range that works for me.

• Revision 1f26840fbf : Enable recursive partition down to 4x4 This commit allows the rate-distortion o

  11 mai 2013, par Jingning Han

  Changed Paths :
   Modify /vp9/common/vp9_blockd.h

  
   Modify /vp9/common/vp9_entropymode.c

  
   Modify /vp9/common/vp9_enums.h

  
   Modify /vp9/decoder/vp9_decodemv.c

  
   Modify /vp9/decoder/vp9_decodframe.c

  
   Modify /vp9/encoder/vp9_bitstream.c

  
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
   Modify /vp9/encoder/vp9_tokenize.c

  
  
  Enable recursive partition down to 4x4

  This commit allows the rate-distortion optimization recursion
  at encoder to go down to 4x4 block size. It deprecates the use
  of I4X4_PRED and SPLITMV syntax elements from bit-stream
  writing/reading. Will remove the unused probability models in
  the next patch.

  The partition type search and bit-stream are now capable of
  supporting the rectangular partition of 8x8 block, i.e., 8x4
  and 4x8. Need to revise the rate-distortion parts to get these
  two partition tested in the rd loop.

  Change-Id : I0dfe3b90a1507ad6138db10cc58e6e237a06a9d6