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• How to let ffmpeg encode image to h264 video in realtime using h264_videotoolbox encoder

  2 novembre 2020, par SolskGaer

  I am using h264_videotoolbox encoder to encode an image stream to h264 video, but the generated video is about one second slower than the input, the command I am using is ffmpeg -f mjpeg -r 20 -i pipe:0 -vf scale=600:-2 -vcodec h264_videotoolbox -realtime true -profile:v baseline -b:v 3000k -r 20 -f h264 - , the input and output is handled by my golang program. I also tried libx264 to do the same thing, under -tune zerolatency -profile:v baseline settings I can get exactually what I want, I think with gpu acceleration, the encoding speed should be faster, what did I do wrong ?

  


• Ways to output video using C ?

  18 mars 2015, par Frank Harris

  I do a lot of physical modeling in C, and for a long time I’ve been using a roundabout way of animating these models ; grid the system to an array of chars and write to a numerically ordered PPM file, then use convert *.ppm video.gif and wait. The output is fine, the time it takes to run ? Not so much. It can take a handful of minutes to produce a video from a simulation that takes a second to run.

  I’m convinced that there must be a more efficient way. The first thing I tried was SDL ; I was able to produce video with it, but I’m doing this on a remote server, and SDL’s performance over SSH is beyond abysmal. Maybe 0.7 FPS.

  I’ve tried using ffmpeg as well, but I haven’t had luck with getting it to work ; not sure why. If there’s no better solution I’ll renew efforts in solving the ffmpeg problem.

  Ideally, I’d like a simple way to avoid outputting all those intermediate files in the first place. Are there any C libraries that would allow me to sequentially combine pixel arrays into frames of an animation ? Preferably relatively simple ?

• file already in use FFmpeg

  11 septembre 2018, par boandriy

  I am running a server that stores video files. When the file is uploaded I run the method below to compress it :

  private void compressVideo(String fileName) throws IOException
  
  {
  
       String cmd[] = {"location to my ffmpeg.exe","-y", "-i", 
  
                              "location to my inputfile"+fileName,"-vcodec","libx264","-crf","20",
  
                              "location to my output file"+fileName};
  
              Runtime.getRuntime().exec(cmd);
  
  
  
  }

  It works fine if my output fileName is different from input fileName.

  But when I run the program with the same names, FFmpeg clearly starts the process but it is not ended (after that I can’t open the overwritten file, it tells me that file is in use by FFmpeg).

  There is no error followed in the console.

  I have tried doing the same thing without running the server and it worked.

  As I am the beginner, I would like to know if I made any mistakes ?
  Any ideas how can I solve this problem ?

  Thanks in advance !