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• lavu/tx : invert permutation lookups

  27 février 2021, par Lynne

  lavu/tx : invert permutation lookups
  out[lut[i]] = in[i] lookups were 4.04 times(!) slower than
  
  out[i] = in[lut[i]] lookups for an out-of-place FFT of length 4096.
  The permutes remain unchanged for anything but out-of-place monolithic
  
  FFT, as those benefit quite a lot from the current order (it means
  
  there's only 1 lookup necessary to add to an offset, rather than
  
  a full gather).
  The code was based around non-power-of-two FFTs, so this wasn't
  
  benchmarked early on.
  

  • [DH] libavutil/tx.c
  • [DH] libavutil/tx_priv.h
  • [DH] libavutil/tx_template.c

• How can I avoid an ffmpeg out of memory error

  21 mars 2021, par Silentfury

  I use ffmpeg with complex filtering. Input are different sets of FULLHD surveilance camera videos each 10 to 15 seconds long. Set size (number of videos per set) varies. To remove unchanged frames I apply mpdecimate. To avoid being triggered by moving bushes but still keep objects I want to remain, I apply a complex filter :

  


  

  • split the video (the original and a dummy to detect motion/stills)

  


  • scale the dummy down (so the 8x8-block-metric of mpdecimate matches the size of moving objects I want to keep)

  


  • add white boxes to dummy to mask unintendedly moving objects

  


  • apply mpdecimate to dummy to remove non-changing frames

  


  • scale dummy back to original size

  


  • overlay the remaining frames of dummy with matching frames of original

  


  


  All this works fine if the number of input videos is small (less than 100). The memory consupmtion of the ffmpeg process varies somewhere between 2GiB and 5GiB.

  


  If the number of input files gets larger (say 200), the memory consumption suddenly jumps to insane numbers until memory (32GiB plus 33GiB swap) runs out and ffmpeg gets killed. I can not predict if and why this happens. I have one example, where a set of 340 videos worked using 6GiB. Any other set above 100 videos I tried eats all RAM in under two minutes and dies.

  


  There is no particular error message from ffmpeg.

  


  dmesg says :

  


  Out of memory: Kill process 29173 (ffmpeg)
Killed process 29173 (ffmpeg) total-vm:66707800kB


  


  My ffmpeg command :

  


  ffmpeg -f concat -safe 0 -i vidlist -vf 'split=2[full][masked];[masked]scale=w=iw/4:h=ih/4,drawbox=w=51:h=153:x=101:y=0:t=fill:c=white,drawbox=w=74:h=67:x=86:y=49:t=fill:c=white,drawbox=w=51:h=149:x=258:y=0:t=fill:c=white,drawbox=w=13:h=20:x=214:y=103:t=fill:c=white,drawbox=w=29:h=54:x=429:y=40:t=fill:c=white,drawbox=w=35:h=49:x=360:y=111:t=fill:c=white,drawbox=w=26:h=54:x=304:y=92:t=fill:c=white,drawbox=w=48:h=27:x=356:y=105:t=fill:c=white,drawbox=w=30:h=27:x=188:y=124:t=fill:c=white,drawbox=w=50:h=54:x=371:y=7:t=fill:c=white,drawbox=w=18:h=38:x=248:y=107:t=fill:c=white,drawbox=w=21:h=51:x=242:y=33:t=fill:c=white,mpdecimate=hi=64*80:lo=64*40:frac=0.001,scale=w=iw*4:h=ih*4[deduped];[deduped][full]overlay=shortest=1,setpts=N/(15*TB),mpdecimate=hi=64*80:lo=64*50:frac=0.001,setpts=N/(15*TB)' -r 15 -c:v libx265 -preset slower -crf 37 -pix_fmt yuv420p -an result.mkv


  


  ffmpeg version 4.1.6

  


  Debian 4.19.171-2

  


  I hope that my filter can be tuned in some way that achieves the same result but doesn't eat RAM that much - but I have no clue how. Within reasonable limits, I wouldn't mind if processing time suffers. Any hints appreciated.

  


• ffmpeg doesn't respect the transparency of the overlayed image by default

  12 avril 2021, par user15602767

  Here is what I am running

  


  ffmpeg -i urban_pop.mp4 -i C:/Users/hp/Documents/Projects/raceit/logos/logo.png -filter_complex "overlay=540:95" output.mp4


  


  But the original image has transparent areas and opaque areas. I want the transparent areas to remain transparent so that we can see the video through those areas. How can I do it ?

  


  As per docs here I can see it should respoect transparency by default
https://ffmpeg.org/ffmpeg-filters.html#Examples-88
Help me understand what I am doing wrong

  


  Note that I am not talking about customizing the overall transparency of the image while overlaying, but to load the image itself maintaining its original transparency