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• ffmpeg bitrate error when trying to capture frames at intervals from a video

  25 octobre 2011, par TheShaggyBeard

  Here is the error I get from running this script :

  [mjpeg @ 0x8559710]bitrate tolerance too small for bitrate
  Error while opening codec for output stream #0.0 - maybe incorrect parameters such as bit_rate, rate, width or height

  So here is what I am trying to do - I want to automate creating animated gif previews from a video file (in this case I know they will always be a specific format being mp4). Here is what I have :

  echo 'Save the file-name and make a folder named "filenamemp4"'
  
  fileName=$(find . -type f -name "*.mp4")
  
  folderName=$( cat $fileName | grep -o [[:alnum:]] | tr -d '\n' | cat)
  
  
  
  echo 'Grab the frame rate and total number of frames and put them into xaa and xab'
  
  qtinfo asa.mp4 | awk 'NR = 1 { print $2 }' | grep -o "^[0-9]*" | split -l 1
  
  
  
  echo 'Assign values to variable'
  
  frameRate=$(cat xaa)
  
  frameTotal=$(cat xab)
  
  videoLength=$(expr $frameTotal / $frameRate)
  
  
  
  echo 'Take a screenshot at 10% intervals - this is the part that gives me a bitrate error.  It says that the -r option has an invalid input being 1 / value of videoLength' 
  
  ffmpeg -i $fileName -y -ss $videoLength -an -sameq -f image2 -s 'qcif' -r $(expr 1/$videoLength) preview%02d.jpg
  
  
  
  echo 'Take the jpgs and mash them into an animated gif'
  
  convert -delay 50 -loop 10 preview*.jpg preview.gif
  
  
  
  echo 'Move the gif to the specified folder'
  
  mv preview.gif $folderName/preview.gif
  
  
  
  echo 'Clean Up'
  
  find . -type f -name "*.jpg" -exec rm -rf {} \;

  So perhaps there is a better way of doing this, or I am understanding how to use the -r option of ffmpeg wrong. In the tutorial I read on ffmpeg for a similar scenario, they used -r 1/5 to produce frames with a 5 second interval. My assumption is that for the desired interval you want, you just slap it in the denominator for the -r option.

• Revision 91d223bd5c : Some minor optimizations for cost_coeffs(). Cycle timings for first 3 frames of

  28 juin 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_encodemb.c

  
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Some minor optimizations for cost_coeffs().

  Cycle timings for first 3 frames of bus (speed 0) at 1500kbps :
  4x4 : 298 -> 234 cycles
  8x8 : 1227 -> 878 cycles
  16x16 : 23426 -> 18134 cycles
  32x32 : 4906 -> 3664 cycles

  Total encode time of first 50 frames of bus @ 1500kbps (speed 0) goes
  from 3min0.7 to 2min51.6 seconds, i.e. 5.3% faster.

  Change-Id : I68a0e1b530b0563b84a67342cca4b45146077e95

• Revision 1ff94fea56 : Inline vp9_quantize() in xform_quant(). Cycle times : 4x4 : 151 to 131 cycles

  11 juillet 2013, par Ronald S. Bultje

  Changed Paths :
   Modify /vp9/encoder/vp9_encodemb.c

  
   Modify /vp9/encoder/vp9_quantize.c

  
   Modify /vp9/encoder/vp9_quantize.h

  
  
  Inline vp9_quantize() in xform_quant().

  Cycle times :
  4x4 : 151 to 131 cycles (15% faster)
  8x8 : 334 to 306 cycles (9% faster)
  16x16 : 1401 to 1368 cycles (2.5% faster)
  32x32 : 7403 to 7367 cycles (0.5% faster)

  Total encode time of first 50 frames of bus @ 1500kbps (speed 0)
  goes from 1min39.2 to 1min38.6, i.e. a 0.67% overall speedup.

  Change-Id : I799a49460e5e3fcab01725564dd49c629bfe935f