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• FFmpeg screencast recording : which codecs to use ?

  24 avril 2013, par mkaito

  I've been experimenting with recording screencasts using FFmpeg's X11grab module, which has worked more or less fine so far. I understand that a/v encoding is a complex process with many fine details, but I'm doing my best to learn.

  I'd like to do "lightweight" recording of a video stream, that puts as little strain as possible on the system while the stream is being recorded. I record two audio streams separately with pacat and sox. Later, the whole thing is filtered, normalized, encoded, and combined into a Matroska container.

  Right now, I'm having ffmpeg record a rawvideo stream to be fed to x264's yuv4 demuxer. I experimented with ffv1 and straight x264 recording before. My system can't handle real time encoding with x264 on the settings I want for the final stream, so I have to recompress separately once the recording is done. I've found that ffv1 gives me terrible frame dropping, and yuv4 too, but less so. I suspect this is due to hard drive speed, even if I'm sitting in a SATA3 Caviar Black that's being used exclusively to hold the recorded data.

  The question is, which combination of video codecs should I look at ? Record straight in x264 and recompress to "better" x264 later ? Raw video, then compress ? How would I go about pinpointing issues such as the frame drops I've been experiencing ?

  EDIT : This is the ffmpeg line I currently use.

  ffmpeg -v warning -f x11grab -s 1920x1080 -r 30000/1001 -i :0.0\
  
  -vcodec rawvideo -pix_fmt yuv420p -s 1280x720\
  
  -threads 0\
  
  recvideo.y4m

• AForge.Video.FFMPEG used in C#

  17 janvier 2017, par cuong nguyen

  I use Visual C# 2008 and want to write AVI file from bmp sequences.

  I found AForge.Video.VWF but it’s just for "vmw3" or "DIB " codecs and I want to use AForge.Video.FFMPEG but it got error.

  For example I just code :

  using System;
  
  using System.Collections.Generic;
  
  
  
  using System.Linq;
  
  using System.Text;
  
  using AForge.Video.FFMPEG;
  
  
  
  namespace ConsoleApplication4
  
  {
  
      class Program
  
      {
  
          static void Main(string[] args)
  
          {
  
              VideoFileWriter vfw = new VideoFileWriter();
  
          }
  
      }
  
  }

  But I got this filenotfoundexception

  {"The specified module could not be found. (Exception from HRESULT: 0x8007007E)":null}

• Capturing snapshot works on one RTSP stream and fails on another

  29 mars 2012, par Saurabh Gandhi

  I am using the VLM feature (over telnet) of VLC to re-stream a live camera RTSP stream using VOD (video on demand). This provides me with two options of viewing the live stream :

  1. Original camera stream
  2. VOD stream generated using VLM

  Both these streams are working fine when viewed within VLC player. I would like to take a snapshot from both these streams whenever the user presses a key. So, I am using command-line vlc interface to grab a snapshot, the command for which is :

  • Snapshot from original camera stream (Case I)

  cvlc -V dummy --video-filter scene --scene-format jpeg --scene-prefix myscene --start-time=0 --stop-time=1 --scene-replace --scene-path /var/www/ <original camera="camera" stream="stream"> vlc://quit;
  
  </original>

  • Snapshot from VOD stream (Case II)

  cvlc -V dummy --video-filter scene --scene-format jpeg --scene-prefix myscene --start-time=0 --stop-time=1 --scene-replace --scene-path /var/www/ <vod stream="stream" generated="generated" using="using" vlm="vlm"> vlc://quit;
  
  </vod>

  Now, case I seems to work fine but case II does not work, in-spite of confirming that both the live streams are working fine. What could be the problem ?

  Here are the logs of VLC when case II is executed on command-line :

  saurabh@saurabh-Latitude-E5510:~/Desktop/html_trial$ cvlc -V dummy --video-filter scene --scene-format jpeg --scene-prefix myscene --start-time=0 --stop-time=1 --scene-replace --scene-path /var/www/ rtsp://10.17.1.150:5544/vid1 vlc://quit; 
  
  
  
  VLC media player 1.1.9 The Luggage (revision exported) 
  
  Blocked: call to unsetenv("DBUS_ACTIVATION_ADDRESS") 
  
  Blocked: call to unsetenv("DBUS_ACTIVATION_BUS_TYPE") 
  
  [0x97c684c] dummy interface: using the dummy interface module... 
  
  rc buffer underflow 
  
  rc buffer underflow 
  
  rc buffer underflow 
  
  rc buffer underflow 
  
  ^C[0x97be2ac] signals interface error: Caught Interrupt signal, exiting...

  Regards,

  Saurabh Gandhi