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• Recording video in C#

  30 décembre 2022, par pfedotovsky

  I have to do the following : record video from a camera using C#. The camera I use produces video frames (the frame rate is not fixed) and I have to somehow put all the frames together and create a video file. Also I need to use different codecs, such as AVI or MPEG-4 (these codecs are required, others are optional).

  


  The main problem I faced was how to create a video in which the frame rate is not fixed. I have a stream of frames. For example, I can receive the first frame after 1 ms, then after 20 ms, then 36 ms and so on. If I create video with 25 frames/second the result will be wrong because it means that frames are added after 40 ms.

  


  I tried to use Aforge.Video library. It has a method which adds a frame according to a timespan. But this method has problems with setting the bitrate. The bitrate value I pass to the method is simply ignored (About an FFmpeg bitrate and framerate issue).

  


  Is there some C# library which I can use to do video recording ? I have to support AVI and MPEG-4, and also the possibility to set the bitrate and last but not least - record video with a variable framerate.

  


  I can't connect to the camera directly. All I have is a stream of frames and I need to convert this stream to video at run time.

  


  A library I'm looking for should satisfy the following properties. It has to contain a method (or some way how to do the same) to add the next frame with a timestamp, just like in Aforge.Video.FFMPEG :

  


  public void WriteVideoFrame(Bitmap frame, TimeSpan timestamp)


  


  And it should be possible to choose different codecs (at least AVI and MPEG-4) and also to set bitrate.
Are there some alternatives to Aforge.Video.FFMPEG ? Because Aforge doesn't work properly. The bitrate value is ignored, and also some codecs are not supported (MPEG-2 for example).

  


  About the codec license. If I use an open source library, should I worry about the codec license ?

  


• Yes or no, will ffmpeg api do hardware decoding on iOS ?

  15 janvier 2019, par Fattie

  There seems to be conflicting information on this.

  https://trac.ffmpeg.org/wiki/HWAccelIntro

  notice the first diagram, it firmly marks iOS as “Y” on VideoToolbox

  

  however in the comments down the bottom it says

  VideoToolbox. ​VideoToolbox, only supported on macOS. H.264 decoding is available in FFmpeg/libavcodec.

  And in the confusing second diagram it says "Standalone" is not done for VideoToolbox.

  We have found that using ffmpeg compiled in to iOS .... it seems to not use hardware decoding, which is really a pain.

  1. With avcodec_get_hw_config() we get AV_PIX_FMT_VIDEOTOOLBOX, AV_HWDEVICE_TYPE_VIDEOTOOLBOX which is seemingly correct.

  2. But usage and framerates clearly shows everything is being done in CPU. The code is in ff_hevc_hls_residual_coding all the time. (That’s fffmpeg’s software decoder.)

  3. This very diff very long git.videolan.org URL here seems to suggest again it should all be working.

  4. Have tried every iPhone etc. of course

• sh : ffmpeg : command not found when run command through php

  9 avril 2015, par Ashok

  I have installed successfully installed FFMpeg on root of my Centos 6 machine (https://trac.ffmpeg.org/wiki/CompilationGuide/Centos).

  My workplace of apache/php is /var/www/html

  Now I’m running below command successfully on /var/www/html directory to capture frame from the video file. It’s capturing a frame.

  [root@localhost html]# ffmpeg -i video.mpg -an -ss 30  -t 00:00:01 -r 1 -y -vcodec mjpeg -f mjpeg -s 160x100 frame8  2>&1

  I want to run this command through php and using shell_exec() or exec() php functions. My php code for running the command is :

  $cmd = "/root/bin/ffmpeg -i /project/app/webroot/videos/video.mpg -ss 00:00:14.435 -f image2 -vframes 1 /project/app/webroot/videothumbnails/example-thumb.jpg";
  
  $locale = 'en_IN.UTF-8';
  
  setlocale(LC_ALL, $locale);
  
  putenv('LC_ALL='.$locale);
  
  echo shell_exec($cmd);

  When I’m trying to run command through above php code, I’m getting below error :

  sh: ffmpeg: command not found

  Please help me to solve out this problem.