Recherche avancée

Sur d’autres sites (4198)

• ffmpeg fails to capture video running on screen

  21 septembre 2014, par Ralf

  I’m trying to capture a slide presentation as video. I’m using the following command to capture my screen

  ffmpeg \
  
     -f x11grab -s 1024x768 -r 25 -i $DISPLAY \
  
     -f alsa -i pulse \
  
     -vcodec libx264 -preset ultrafast -vb 1000k \
  
     -acodec libmp3lame -ab 128k \
  
     test.avi

  This works (application windows on the screen are visible and sound is recorded in test.avi), but the problem is : Any video shown on the screen (e.g. a youtube video running in a browser window, but also e.g. a video played by mplayer) only appears as an empty (e.g. green) box when I play the captured video (test.avi).

  I’m using ffmpeg version 0.8.16-4:0.8.16-0ubuntu0.12.04.1 on Ubuntu 12.04.5 LTS with the nvidia-331 driver (effect is the same with older nvidia-304).

  I would really appreciate any suggestions, thanks a lot !

• Forward youtube-dl output to ffmpeg with hardware-accelerated encoding [closed]

  16 mars 2021, par Yehor

  I'm trying to download some videos from youtube and simultaneously forward those to ffmpeg for hardware decoding to h265 (just for purpose of seeing how it works).

  


  My command, that works, but uses (as I understand) software encoding :

  


  youtube-dl -o "./%(playlist)s/%(title)s.%(ext)s" --merge-output-format mkv --postprocessor-args "-c:v libx265 -c:a opus -strict experimental" "target_url"


  


  When I specify the hardware acceleration, I receive the error "Invalid argument". The command is :

  


  youtube-dl -o "./%(playlist)s/%(title)s.%(ext)s" --merge-output-format mkv --postprocessor-args "-hwaccel cuda -c:v hevc_nvenc -c:a opus -strict experimental" "target_url"


  


  What I've done wrong ?

  


  System info :

  


  

  • OS : Windows 10 x64

  


  • GPU : Nvidia GeForce 960M (installed the latest driver and CUDA) and should be supported by CUDA

  


  • latest youtube-dl and ffmpeg build

  


  


  The ffmpeg -encoders output contains 265 codecs, so they also should be supported :

  


  V..... libx265              libx265 H.265 / HEVC (codec hevc)
V..... nvenc_hevc           NVIDIA NVENC hevc encoder (codec hevc)
V..... hevc_amf             AMD AMF HEVC encoder (codec hevc)
V..... hevc_nvenc           NVIDIA NVENC hevc encoder (codec hevc)
V..... hevc_qsv             HEVC (Intel Quick Sync Video acceleration) (codec hevc)


  


• Nvenc session limit per GPU

  4 juin 2020, par teals

  I'm using Imageio, the python library that wraps around ffmpeg to do hardware encoding via nvenc. My issue is that I can't get more than 2 sessions to launch (I am using non-quadro GPUs). Even using multiple GPUs. I looked over NVIDIA's support matrix and they state only 2 sessions per gpu, but it seems to be per system.

  



  For example I have 2 GPUs in a system. I can either use the env variable CUDA_VISIBLE_DEVICES or set the ffmpeg flag -gpu to select the GPU. I've verified gpu usage using Nvidia-smi cli. I can get 2 encoding sessions working on a single gpu. Or 1 session working on 2 separate gpus each. But I can't get 2 encoding sessions working on 2 gpus.

  



  Even more strangely if I add more gpus I am still stuck at 2 sessions. I can't launch a third encoding session on a 3rd gpu. I am always stuck at 2 regardless of the # of gpus. Any ideas on how to fix this ?