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• Implementing picture zoom effect using Rmagick and FFmpeg

  26 juin 2013, par DenisKo

  I have a picture and I need to get zoom effect on the resulting video. I almost get the desired result.. but. The resulting picture looks a bit shaky. It's because of rounding on cropping and resizing.. so centre of the picture shifts slightly with each conversion. What can i do with that ? Or maybe there is some other method to implement it ?
  In the input I have
  picture,zoom_type,zoom_percent,zoom_duration,scene_duration
  Here is part of the code which making the job :

  img = Magick::ImageList.new(picture).first
  
  width, height = img.columns.to_f, img.rows.to_f
  
  img_fps = 30
  
  if width >= height
  
    aspect_ratio = (width / height)
  
    zoom_small_size = ((height * (100 - zoom_percent)) / 100).to_f
  
    small_size = height
  
  else
  
    aspect_ratio = (height / width)
  
    zoom_small_size = ((width * (100 - zoom_percent)) / 100).to_f
  
    small_size = width
  
  end
  
  factor = (((small_size - zoom_small_size) / (img_fps * zoom_duration))).to_f
  
  while factor < 2
  
    img_fps -= 1
  
    factor = ((small_size - zoom_small_size) / (img_fps * zoom_duration))
  
  end
  
  total_images = img_fps * scene_duration
  
  zoom_images = img_fps * zoom_duration_seed
  
  new_width =  width
  
  new_height =  height
  
  zoom_changed_small_size = small_size
  
  
  
  total_images.times do |i|
  
  if zoom_images > 0 && zoom_changed_small_size > zoom_small_size
  
    img_n = img.crop(new_width, new_height, true)
  
    new_width = (width <= height) ? (new_width - factor).round : (new_width-factor*aspect_ratio).round
  
    new_height = (width >= height) ? (new_height-factor).round : (new_height-factor*aspect_ratio).round
  
    zoom_changed_small_size = (width >= height) ? img_n.rows : img_n.columns
  
    img_n.resize_to_fill!(width, height)
  
    img_n.write("#{sprintf("img_%04d.jpg" % (i+1))}")
  
    zoom_images -= 1
  
    img = img_n.copy if zoom_images == 0 || zoom_changed_small_size <= zoom_small_size
  
    img_n.destroy!
  
  else
  
    img.write("#{sprintf("img_%04d.jpg" % (i+1))}")
  
    puts "Writing - #{img.filename}"
  
  end
  
  end

  Then ffmpeg -y -f image2 -r 30 -i img_%04d.jpg -crf 0 -preset ultrafast -tune stillimage -pix_fmt yuv420p out.mp4

• avformat/argo_{asf,brp} : use variable frame sizes when (de)muxing adpcm_argo

  15 septembre 2020, par Zane van Iperen

  avformat/argo_asf,brp : use variable frame sizes when (de)muxing adpcm_argo
  Signed-off-by : Zane van Iperen <zane@zanevaniperen.com>
  

  • [DH] libavformat/argo_asf.c
  • [DH] libavformat/argo_brp.c

• how to get 120fps encoded video to play at "normal" speed instead of slow mo

  1er mars 2023, par Patrick Vellia

  I used my GoPro Hero10 to record at 4k 120fps on a green screen. This original video plays slo-mo in QuickTime but "normal" speed in the browser. I want it playing normal speed, and if end user wants to slow it down they have the extra frames for that to maintain clarity, which is why I record at 120.

  


  I then used FFMPEG to create an image sequence of the video.

  


  Then I ran Image Magic to create the transparent frames.

  


  Then I put it back together with the following command for a HEVC mov file :

  


  ffmpeg -r 120 -f image2 -i transparent/image_transparent_%08d.png -vcodec hevc_videotoolbox -crf 28 -alpha_quality 1  -tag:v hvc1 output.mov


  


  I am still on an Intel MacBook Pro running FFMPEG 4.6 (as I've found 5+ was buggy with one of my commands a few months ago but can't remember which one, I think it was the videotoolbox).

  


  The GoPro video has the following stream data as input to the FFMPEG :

  


  Duration: 00:00:08.15, start: 0.000000, bitrate: 60160 kb/s
  Stream #0:0(eng): Video: hevc (Main) (hvc1 / 0x31637668), yuvj420p(pc, bt709), 3840x2160 [SAR 1:1 DAR 16:9], 59891 kb/s, 119.88 fps, 119.88 tbr, 120k tbn, 119.88 tbc (default)
    Metadata:
      creation_time   : 2023-02-28T19:06:41.000000Z
      handler_name    : GoPro H.265
      vendor_id       : [0][0][0][0]
      encoder         : GoPro H.265 encoder
      timecode        : 19:05:32:105
  Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 189 kb/s (default)
    Metadata:
      creation_time   : 2023-02-28T19:06:41.000000Z
      handler_name    : GoPro AAC  
      vendor_id       : [0][0][0][0]
      timecode        : 19:05:32:105
  Stream #0:2(eng): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
    Metadata:
      creation_time   : 2023-02-28T19:06:41.000000Z
      handler_name    : GoPro TCD  
      timecode        : 19:05:32:105
  Stream #0:3(eng): Data: bin_data (gpmd / 0x646D7067), 76 kb/s (default)
    Metadata:
      creation_time   : 2023-02-28T19:06:41.000000Z
      handler_name    : GoPro MET  


  


  Whereas the re-constructed video has the following data :

  


  Duration: 00:00:08.13, start: 0.000000, bitrate: 763650 kb/s
  Stream #0:0: Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv, progressive), 3840x2160 [SAR 1:1 DAR 16:9], 763696 kb/s, 120 fps, 120 tbr, 15360 tbn, 15360 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : FFMP
      encoder         : Lavc58.134.100 hevc_videotoolbo


  


  When this re-constructed video plays in the browser, it is in slow-mo and I need to set the playbackRate to 4.0 for it to play "normally".

  


  Is there something I need to add to the video for the browser to play it at "normal" speed ?

  


  EDIT

  


  I just compared the two video streams :

  


  original:
Stream #0:0(eng): Video: hevc (Main) (hvc1 / 0x31637668), yuvj420p(pc, bt709), 3840x2160 [SAR 1:1 DAR 16:9], 59891 kb/s, 119.88 fps, 119.88 tbr, 120k tbn, 119.88 tbc (default)

Reconstructed:
 Stream #0:0: Video: hevc (Main) (hvc1 / 0x31637668), yuv420p(tv, progressive), 3840x2160 [SAR 1:1 DAR 16:9], 763696 kb/s, 120 fps, 120 tbr, 15360 tbn, 15360 tbc (default)


  


  I don't quit understand all of this though. so here's what I notice :

  


  original.         reconstructed
--------------------------------
bt709             progressive
89871 kb/s.       763696 kb/s
119.88 fps.       120 fps
119.88 tbr.       120 tbr
120k tbr.         15360 tbr
11960 tbr.        15360 tbc


  


  Hmm. I suspect it has something to do with tbr and tbc whatever those are, or perhaps the progressive vs the bt709 ? the pirates are also vastly different.