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• FFMPEG Concat Dropping Frames

  16 mars 2015, par scientiffic

  I’m using FFMPEG to do the following two things :

  • create an mp4 given a set of images
  • compile mp4s to create a longer video (mp4)

  To create mp4s from images, I use the following command :

  ffmpeg -r 5 -i 'img%03d.jpg' output.mp4

  As far as I know, this creates a video with a framerate of 5fps.

  But when I try to compile mp4s, it seems like frames within each mp4 are being dropped.

  To create the compiled footage, I create a text file that points to all the mp4s that should be included in the compilation, e.g.

  file 'set1/output.mp4'
  
  file 'set2/output.mp4'
  
  file 'set3/output.mp4'
  
  file 'set4/output.mp4'
  
  file 'set5/output.mp4'
  
  file 'set6/output.mp4'
  
  file 'set7/output.mp4'

  Then I run the following command :

  ffmpeg -f concat -i input.txt -codec copy compilation.mp4

  The resulting video seems to drop 2-3 frames from each of the output videos.

  How do I ensure that the compiled video doesn’t drop any frames ?

  (For reference, I used the following tutorial : https://trac.ffmpeg.org/wiki/Concatenate)

• 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 ?

  


• ffmpeg command to GStreamer pipeline for srtp stream

  1er avril 2021, par Muhammet Ilendemli

  I would like to convert this working ffmpeg command to a GStreamer pipeline but I couldn't manage to get it working. Tried using srtpenc toset the key to a hex representation of the buffer and udpsink with the target host and port set.

  



  The command I currently have :

  



  ffmpeg -re -i &lt;<rtspurl>> -map 0:0 -vcodec h264_omx -pix_fmt yuv420p \&#xA;  -r 30 -f rawvideo -tune zerolatency -vf scale=1280:720 -b:v 300k \&#xA;  -bufsize 300k -payload_type 99 -ssrc &lt;<ssrc>> \&#xA;  -f rtp -srtp_out_suite AES_CM_128_HMAC_SHA1_80 \&#xA;  -srtp_out_params &lt;<base64key>> srtp://&lt;<targetip>>:&lt;<targetport>>?rtcpport=&lt;<targetport>>&amp;localrtcpport=&lt;<targetport>>&amp;pkt_size=1378&#xA;</targetport></targetport></targetport></targetip></base64key></ssrc></rtspurl>

  



  Some references :

  



  


  • https://github.com/KhaosT/HAP-NodeJS/blob/master/src/lib/Camera.ts

  


  • https://github.com/KhaosT/HAP-NodeJS/wiki/IP-Camera#prepare-stream