Recherche avancée

Sur d’autres sites (4224)

• What is the best gpu in the market for video encoding (H.264 and H.265) [closed]

  12 août 2020, par Hamza Ghizaoui

  So, I m using FFMPEG for video encoding.
I get a stream of BMP images, each with 4000x3000 resoltuion. 20 Image per second (image size circa 35 mbyte).
I must encode that and stream it in real time. a maximum of 100 ms is allowed between ghe moment of receiving the photo and the moment of displaying that on the browser.

  


  I m using FFMPEG with nvidia nvenc hardware accelration .

  


  maximum budget is 2000$ for the GPU.

  


• FFmpeg CRF control using x264 vs libvpx-vp9

  19 octobre 2016, par igon

  I have some experience using ffmpeg with x264 and I wanted to do a comparison with libvpx-vp9. I tested a simple single pass encoding of a raw video, varying the crf settings and presets both with x264 and libvpx-vp9. I am new to libvpx and I followed this and this carefully but I might have still specified wrong combination of parameters since the results I get do not make much sense to me.

  For x264 I did :

  ffmpeg -i test_video.y4m -c:v libx264 -threads 1 -crf <crf> -preset <preset> -y output.mkv 
  
  </preset></crf>

  and obtained the following results :

  codec  , settings                        , time        , PSNR      ,bitrate
  
  libx264,['-crf', '20', '-preset', 'fast'],13.1897280216, 42.938337 ,15728
  
  libx264,['-crf', '20', '-preset', 'medium'],16.80494689, 42.879753 ,15287
  
  libx264,['-crf', '20', '-preset', 'slow'],25.1142120361, 42.919206 ,15400
  
  libx264,['-crf', '30', '-preset', 'fast'],8.79047083855, 37.975141 ,4106
  
  libx264,['-crf', '30', '-preset', 'medium'],9.936599016, 37.713778 ,3749
  
  libx264,['-crf', '30', '-preset', 'slow'],13.0959510803, 37.569511 ,3555

  This makes sense to me, given a crf value you get a value of PSNR and changing the preset can decrease the bitrate but increase the time to encode.

  For libvpx-vp9 I did :

  ffmpeg -i test_video.y4m -c:v libvpx-vp9 -threads 1 -crf <crf> -cpu-used <effort> -y output.mkv 
  
  </effort></crf>

  First of all I thought from tutorials online that the -cpu-used option is equivalent to -preset in x264. Is that correct ? If so what is the difference with -quality ? Furthermore since the range goes from -8 to 8 I assumed that negative values where the fast options while positive values the slowest. Results I get are very confusing though :

  codec     , settings                      , time        , PSNR     ,bitrate
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '-2'],19.6644911766,32.54317,571
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '0'],176.670887947,32.69899,564
  
  libvpx-vp9,['-crf', '20', '-cpu-used', '2'],20.0206270218,32.54317,571
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '-2'],19.7931578159,32.54317,571
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '0'],176.587754965,32.69899,564
  
  libvpx-vp9,['-crf', '30', '-cpu-used', '2'],19.8394429684,32.54317,571

  Bitrate is very low and PSNR seems unaffected by the crf setting (and very low compared to x264). The -cpu-used setting has very minimal impact and also seems that -2 and 2 are the same option.. What am I missing ? I expected libvpx to take more time to encode (which is definitely true) but at the same time higher quality transcodes. What parameters should I use to
  have a fair comparison with x264 ?

  Edit : Thanks to @mulvya and this doc I figured that to work in crf mode with libvpx I have to add -b:v 0. I re-ran my tests and I get :

      codec     , settings                                 , time        , PSNR     ,bitrate
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '-2'],57.6835780144,45.111158,17908
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '0'] ,401.360313892,45.285367,17431
  
  libvpx-vp9,['-crf', '20', '-b:v', '0', '-cpu-used', '2'] ,57.4941239357,45.111158,17908
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '-2'],49.175855875,42.588178,11085
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '0'] ,347.158324957,42.782194,10935
  
  libvpx-vp9,['-crf', '30', '-b:v', '0', '-cpu-used', '2'] ,49.1892938614,42.588178,11085

  PSNR and bitrate went up significantly by adding -b:v 0

• FFMPEG Cannot Init CUDA

  7 novembre 2016, par Alan

  I am working to install ffmpeg with hardware GPU support on a Xenserver virtual server (Ubuntu 16.04). I am following the guide from : http://developer.download.nvidia.com/compute/redist/ffmpeg/1511-patch/FFMPEG-with-NVIDIA-Acceleration-on-Ubuntu_UG_v01.pdf

  While updating the directions for the newest versions of the SDK and versions for 16.04. I have everything built and all seems fine when doing version checks :

  ffmpeg version N-82277-ge2193b5 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.2) 20160609
  
    configuration: --prefix=/root/ffmpeg_build --pkg-config-flags=--static 
  
  --extra-cflags=-I/root/ffmpeg_build/include
  
  --extra-ldflags=-L/root/ffmpeg_build/lib --bindir=/root/bin --enable-gpl --enable-libass --enable-libfdk-aac 
  
  --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx 
  
  --enable-libx264 --enable-libx265 --enable-libvidstab --enable-nonfree --enable-nvenc
  
  
  
  #nvcc --version
  
  nvcc: NVIDIA (R) Cuda compiler driver
  
  Copyright (c) 2005-2015 NVIDIA Corporation
  
  Built on Tue_Aug_11_14:27:32_CDT_2015
  
  Cuda compilation tools, release 7.5, V7.5.17

  When I try doing the test using the GPU I get this :

  #time ffmpeg -y -i 337.mp4 -vcodec h264_nvenc -b:v 5M -acodec copy OUTPUT.mp4
  
  
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '337.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf56.25.101
  
    Duration: 00:00:22.74, start: 0.000000, bitrate: 537 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x480 [SAR 1:1 DAR 3:2], 434 kb/s, 29.97 fps, 29.97 tbr, 11988 tbn, 59.94 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(eng): Audio: mp3 (mp4a / 0x6134706D), 48000 Hz, stereo, s16p, 96 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  modprobe: ERROR: could not insert 'nvidia_367_uvm': No such device
  
  [h264_nvenc @ 0x3da6400] Cannot init CUDA
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> h264 (h264_nvenc))
  
    Stream #0:1 -> #0:1 (copy)
  
  Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  In particular I get an error [h264_nvenc @ 0x3da6400] Cannot init CUDA

  I can’t seem to find any info on this. I am not running any desktop GUI, strictly command line trying to accelerate video encoding with a Nvidia GTX 960.