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• Anomalie #2540 (Fermé) : Onglets a gauche dans l’espace prive en RTL

  18 février 2012, par George Kandalaft

  Apparement je ne peux pas commiter ici. Les onglets simples sur les pages sont encore a gauche en RTL. prive\themes\spip\icon.css.html line 104 : .onglets_simple ul li float:left ;padding:0 ;margin:0 ;margin-bottom :-1px ; Remplacer float:left ; par (...)

• How to apply 'simple 'opacity to combined(layered) mp4s in FFMPEG

  27 mai 2021, par Cam

  I am not getting the final image results I need when layering together multiple mp4s of the same length and format into a single output MP4. I am using ffmpeg to create a pseudo 'motion blur' effect on animation, and need to layer mp4s together with identical opacities to produce the final video.

  


  I am using a base 'black' MP4 as the first layer for a background, and then adding a series of source mp4s with equal opacity over the top in each pass. Here I am showing a photoshop mockup using their 'normal' blending mode which is exactly the blending effect I am trying to replicate with ffmpeg. I understand that the final composite is less "bright" but that's fine (unless you have any ideas).


  


  Instead of looking like the result above, I am getting output where the colors are either all pink, garbled, super dark or generally hugely overbright etc based on trying different blend modes.

  


  Here are the commands I am using :

  


  To create the original (uncompressed ?) 'black' MP4 from a sequence of black pngs :

  


  ffmpeg -start_number 0 -r 24 -f image2 -s 1920x1080 -i black_seq.%04d.png -vcodec libx264 -crf 0 -pix_fmt yuv420p   black_seq.mp4 -y


  


  I then take that "black_seq.mp4" and blend a set of n number of source mp4s over the top with an opacity value. This runs in a loop and the output.mp4 of each pass becomes the input.mp4 of the next pass until it completes. In this example a total of 10 source mp4s assigns their opacity to 0.1 for each pass, and this is a single pass (below). The source mp4s are all very similar in their appearance and color, essentially just the same sequence of animation but offset in time by fractions of a single frame and have been generated from color pngs, using the same code that produced the first black layer (above).

  


  ffmpeg i input.mp4 -i n_layer.mp4 -vcodec libx264 -crf 0 -pix_fmt yuv420p   -filter_complex "blend=all_mode='overlay':all_opacity=0.1" output.mp4 -y


  


  Then finally add some compression to the result as the final "blur.mp4"

  


  ffmpeg -i "output.mp4" -vcodec libx264 -crf 25 -pix_fmt yuv420p "blur.mp4" -y


  


  And yes, this is certainly highly inefficient as an approach, but I am learning. The main issue I am trying to solve is, despite the final blur.mp4 being less "bright", it has colors that are not matching the original animation and instead looks like the animation has been hue shifted somehow.

  


  This image shows a cropped output for comparison (the processed blur is set to zero for clarity)


  


  I would love some insight.

  


• How to Simply Remove Duplicate Frames from a Video using ffmpeg

  29 janvier 2017, par Skeeve

  First of all, I’d preface this by saying I’m NO EXPERT with video manipulation,
  although I’ve been fiddling with ffmpeg for years (in a fairly limited way). Hence, I’m not too flash with all the language folk often use... and how it affects what I’m trying to do in my manipulations... but I’ll have a go with this anyway...

  I’ve checked a few links here, for example :
  ffmpeg - remove sequentially duplicate frames

  ...but the content didn’t really help me.

  I have some hundreds of video clips that have been created under both Windows and Linux using both ffmpeg and other similar applications. However, they have some problems with times in the video where the display is ’motionless’.

  As an example, let’s say we have some web site that streams a live video into, say, a Flash video player/plugin in a web browser. In this case, we’re talking about a traffic camera video stream, for example.

  There’s an instance of ffmpeg running that is capturing a region of the (Windows) desktop into a video file, viz :-

  ffmpeg -hide_banner -y -f dshow ^
  
        -i video="screen-capture-recorder" ^
  
        -vf "setpts=1.00*PTS,crop=448:336:620:360" ^
  
        -an -r 25 -vcodec libx264 -crf 0 -qp 0 ^
  
        -preset ultrafast SAMPLE.flv

  Let’s say the actual ’display’ that is being captured looks like this :-

  123456789 XXXXX 1234567 XXXXXXXXXXX 123456789 XXXXXXX
  
  ^---a---^ ^-P-^ ^--b--^ ^----Q----^ ^---c---^ ^--R--^ 

  ...where each character position represents a (sequence of) frame(s). Owing to a poor internet connection, a "single frame" can be displayed for an extended period (the ’X’ characters being an (almost) exact copy of the immediately previous frame). So this means we have segments of the captured video where the image doesn’t change at all (to the naked eye, anyway).

  How can we deal with the duplicate frames ?... and how does our approach change if the ’duplicates’ are NOT the same to ffmpeg but LOOK more-or-less the same to the viewer ?

  If we simply remove the duplicate frames, the ’pacing’ of the video is lost, and what used to take, maybe, 5 seconds to display, now takes a fraction of a second, giving a very jerky, unnatural motion, although there are no duplicate images in the video. This seems to be achievable using ffmpeg with an ’mp_decimate’ option, viz :-

       ffmpeg -i SAMPLE.flv ^                      ... (i)
  
          -r 25 ^
  
          -vf mpdecimate,setpts=N/FRAME_RATE/TB DEC_SAMPLE.mp4

  That reference I quoted uses a command that shows which frames ’mp_decimate’ will remove when it considers them to be ’the same’, viz :-

       ffmpeg -i SAMPLE.flv ^                      ... (ii)
  
          -vf mpdecimate ^
  
          -loglevel debug -f null -

  ...but knowing that (complicated formatted) information, how can we re-organize the video without executing multiple runs of ffmpeg to extract ’slices’ of video for re-combining later ?

  In that case, I’m guessing we’d have to run something like :-

  • user specifies a ’threshold duration’ for the duplicates
    (maybe run for 1 sec only)
  • determine & save main video information (fps, etc - assuming
    constant frame rate)
  • map the (frame/time where duplicates start)->no. of
    frames/duration of duplicates
  • if the duration of duplicates is less than the user threshold,
    don’t consider this period as a ’series of duplicate frames’
    and move on
  • extract the ’non-duplicate’ video segments (a, b & c in the
    diagram above)
  • create ’new video’ (empty) with original video’s specs
  • for each video segment
    extract the last frame of the segment
    create a short video clip with repeated frames of the frame
    just extracted (duration = user spec. = 1 sec)
    append (current video segment+short clip) to ’new video’
    and repeat

  ...but in my case, a lot of the captured videos might be 30 minutes long and have hundreds of 10 sec long pauses, so the ’rebuilding’ of the videos will take a long time using this method.

  This is why I’m hoping there’s some "reliable" and "more intelligent" way to use
  ffmepg (with/without the ’mp_decimate’ filter) to do the ’decimate’ function in only a couple of passes or so... Maybe there’s a way that the required segments could even be specified (in a text file, for example) and as ffmpeg runs it will
  stop/restart it’s transcoding at specified times/frame numbers ?

  Short of this, is there another application (for use on Windows or Linux) that could do what I’m looking for, without having to manually set start/stop points,
  extracting/combining video segments manually...?

  I’ve been trying to do all this with ffmpeg N-79824-gcaee88d under Win7-SP1 and (a different version I don’t currently remember) under Puppy Linux Slacko 5.6.4.

  Thanks a heap for any clues.