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• Stuck in deadend while compiling ffmpeg with nvidia CUDA support on Ubuntu 18.04 and GeForce GT 730

  24 février 2019, par Marko

  I want to compile ffmpeg with CUDA support, on Ubuntu 18.04, and my graphics card is GeForce GT 730 (so far I have not CUDA programming experience).
  Here nvidia claims that it has at least some transcoding support.

  I have cloned https://git.ffmpeg.org/ffmpeg.git and as I understand I also need to build and install nv-codec-headers.

  But there in the README, they say that minimum driver version for Linux is 418.30 or newer. So I went to nvidia site to download driver and after selecting my card I got this download link. So the driver version is high enough it seems. But when I try to install it I get message that this device will be ignored by that driver and that it is supported by legacy driver 390.xx (which is version I can install with apt).
  Is something wrong with nVidia, why are they offering me driver that is cannot be used for this device ?

  I’ve installed 390.xx driver using ubuntu-drivers autoinstall and built ffmpeg, but when I try to run it I get this error : Cannot load cuvidGetDecodeStatus [h264_cuvid @ 0x562a86dbc680] Failed loading nvcuvid.

  I suppose it is because of driver ?

  So, what can I do to unstuck myself ?

• Video recorded from a webcam using FFmpeg is desynchronizing in iOS native player

  11 mars 2021, par Luuudo

  Objective

  


  I am trying to record a video (duration ≈ 1min to 4hours) from a webcam plugged into a PC. Then play just after the end of the recording the video on an Ipad connected to the same network as the PC.

  


  To do this I'm trying to record the video using ffmpeg (the detailed command I use is below). Then I serve the video that's on the PC to the Ipad via a Java server (The server works well with other videos so I don't think the problem is here).

  


  Problem

  


  When I play the video on the IPad native player, for example in Safari, the sound is going faster than the video and therefore it's desynchronizing from the video. If I request a certain time the video and audio re-sync then the audio is desynchronizing again while playing.

  


  

  • The video when played on VLC on the PC or on Firefox by requesting the server is well synced.

  


  • Another video (I downloaded this one to test) played on the Ipad from the server stay synced.

  


  


  It is only with the combination of a video record by myself using FFmpeg played in the iOS native player that I can observe the desynchronization.

  


  FFmpeg command

  


  I use FFmpeg to record the video from the webcam and save it into a file format readable on iOS.

  


  ffmpeg -y -f avfoundation -framerate 25 -pixel_format nv12 -video_size 1280x720 -i "0:0" -r 25 out.mp4


  


  The resulting recorded file info according to ffmpeg is below :

  


  > ffmpeg -i out.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:00:33.76, start: 0.000000, bitrate: 1510 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 1440 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 61 kb/s (default)
    Metadata:
      handler_name    : SoundHandler


  


  Compatible video formats from TV and Video iPad Pro specs

  


  


  Video formats supported : H.264 video up to 4K, 30 frames per second, High Profile level 4.2 with AAC‑LC audio up to 160 Kbps, 48kHz, stereo audio or Dolby Audio up to 1008 Kbps, 48kHz, stereo or multichannel audio, in .m4v, .mp4, and .mov file formats ; MPEG‑4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC‑LC audio up to 160 Kbps per channel, 48kHz, stereo audio or Dolby Audio up to 1008 Kbps, 48kHz, stereo or multichannel audio, in .m4v, .mp4, and .mov file formats ; Motion JPEG (M‑JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio in .avi file format

  


  


  I don't see what codecs or profiles I don't respect ?

  


  ps : I write PC but I'm currently trying this on a Mac. Eventually, I want to be able to do it also on Linux or even Windows. It looks like I just have to change the input devices to do that, which is avfoundation for MacOS.

  


• What kind of ogg does Android Chrome support ?

  22 février 2014, par Nathan

  I've found that I can only play some ogg vorbis files in Android Chrome. Most notably, I cannot play the ogg files generated by Mauz Kahn's demo here : https://www.webrtc-experiment.com/ffmpeg/wav-to-ogg.html
  I used his demo to create some test ogg files using Windows Chrome and I could play them back while I was using Window's Chrome, but I could not play those same audio files in Android Chrome. I've played other ogg vorbis files in Android chrome so I suspect there is a subtle issue in the parameters that Khan's demo invokes ffmpeg with.