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• what FFMPEG performance settings to use for processing videos for the web

  19 juin 2015, par eAbi

  I have a few questions regarding usage of ffmpeg for processing videos for the web. I’m a beginner so please bear with me (although I read some docs on the internet)

  Performance

  • First of all, given the fact that FFMPEG utilizes all cores at 100%, what is the actual parallelism efficiency ?

  Let’s assume the following scenario. I have a video (fullHD, doesn’t matter what encoders / compression format was used to obtain the video) and I want to resize (downscale) to various sizes (e.g. 240px, 480px and 720px height) using mp4 format (thus using libx264 with aac codecs).

  Using ffmpeg, I see that all of my laptop’s cores (8) are used at 100% and I was wondering what scenarios can improve the overall performance of the whole processing task. So this leads us to basically 2 scenarios : Assuming the video mentioned above as input, for obtaining the 3 output videos (@ 240px, 480px and 720px height sizes), we :

  1. Process input video and obtain 1 output video at a time, and let all the cores work at the same time at 100% ;
  2. Process the video to obtain all output videos in parallel, by bounding each output video to a single processor core which’ll work at 100% ;

  So the question is actually reduced to the parallelism efficiency of the ffmpeg program.

  This means that letting ffmpeg process the task procVideo - which takes 1 input video to produce 1 single output video (transcoding/downscaling and so on) - on N processor cores doesn’t mean it finish the task N times faster than letting it run the same task bound to a single core. So if the efficiency is smaller than 100%, it’s better to have N procVideo tasks in parallel, each bound to a single core, rather than doing the task sequentially for each output video.

  ---

  Codecs

  Other than the above performance problem, the usage of codecs bugs me. I am trying to obtain mp4 videos because of the wide implementation of the format in html5 browsers.

  So having a video as input in any format, I want to convert it to mp4. So I’m using libx264 codec with aac.

  • Use libx264, x264 or h264 for video encoding/decoding ?
  • Use libfdk_aac, libaacplus or aac for audio encoding/decoding to aac ?

  Also, I would like to know what are the licesing fees for each of the above codec, as the online resources on these are quite limited / hard to understand.

  If anyone could shed some light on those questions, I would really be grateful ! Thanks for your time !

• Merge commit ’677c804aa3a78d61b21e6423165a252846c20f0e’

  8 juin 2015, par Michael Niedermayer

  Merge commit ’677c804aa3a78d61b21e6423165a252846c20f0e’
  * commit ’677c804aa3a78d61b21e6423165a252846c20f0e’ :
  
    aac : correctly map 7.1ch-wide AAC from FDK AAC encoder
  Sample : FDK_7.1ch_wide.aac
  
  Merged-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/aacdec.c

• Losslessly convert from RGBA rawvideo to H.264

  11 décembre 2017, par J''

  I am creating a tool that generates frames of RGBA video and pipes it to ffmpeg to create an .mp4 video. Here is the command that I give ffmpeg :

  ffmpeg -y -f rawvideo -vcodec rawvideo -s 960x540 -pix_fmt rgba -r 60 -i - 
  
  -an -c:v libx264 -pix_fmt yuv420p -b:v 995328k vigeo_demo.mp4

  However, the quality is very, very, poor. The video consists of around 2-px wide lines being drawn across the screen at various angles. The lines are very blurry and blocky. What could be the cause of this and how do I fix it ?

  Things I’ve tried :

  • -q:v 0
  • crf 1 (crf 0 gives me an error)