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• Thread count option in FFmpeg for FASTEST conversion to h264 ?

  9 février, par S B

  I need to maximize speed while converting videos using FFmpeg to h264

  



  

  • Any input format of source videos

  


  • User's machine can have any number of cores

  


  • Power and memory consumption are non-issues

  


  



  Of course, there are a whole bunch of options that can be tweaked but this question is particularly about choosing the best -thread <count></count> option. I am trying to find an ideal thread count as a function of

  



  

  • no. of cores

  


  • input video format

  


  • h264-friendly values maybe ?

  


  • anything else missed above ?

  


  



  I am aware the default -thread 0 follows one-thread-per-core approach which is supposed to be optimal. But I am not sure if this is time or space-optimized. Also, on certain testcases, I've seen more threads (say 4 threads on my dual core test machine) finishes quicker than the default.

  



  Any other direction, say configure options w.r.t. threads, worth pursuing ?

  


• Thread count option in FFmpeg for FASTEST conversion to h264 ?

  5 septembre 2013, par Saptarshi Biswas

  I need to maximize speed while converting videos using FFmpeg to h264

  • Any input format of source videos
  • User's machine can have any number of cores
  • Power and memory consumption are non-issues

  Of course, there are a whole bunch of options that can be tweaked but this question is particularly about choosing the best -thread <count></count> option. I am trying to find an ideal thread count as a function of

  • no. of cores
  • input video format
  • h264-friendly values maybe ?
  • anything else missed above ?

  I am aware the default -thread 0 follows one-thread-per-core approach which is supposed to be optimal. But I am not sure if this is time or space-optimized. Also, on certain testcases, I've seen more threads (say 4 threads on my dual core test machine) finishes quicker than the default.

  Any other direction, say configure options w.r.t. threads, worth pursuing ?

• 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