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• Image sequence to video stream ?

  15 novembre 2020, par Hauns TM

  Like many people already seem to have (there are several threads on this subject here) I am looking for ways to create video from a sequence of images.

  



  I want to implement my functionality in C# !

  



  Here is what I wan't to do :

  



  /*Pseudo code*/&#xA;void CreateVideo(List<image> imageSequence, long durationOfEachImageMs, string outputVideoFileName, string outputFormat)&#xA;{&#xA;    // Info: imageSequence.Count will be > 30 000 images&#xA;    // Info: durationOfEachImageMs will be &lt; 300 ms&#xA;&#xA;    if (outputFormat = "mpeg")&#xA;    {&#xA;    }&#xA;    else if (outputFormat = "avi")&#xA;    {      &#xA;    }&#xA;    else&#xA;    {&#xA;    }&#xA;&#xA;    //Save video file do disk&#xA;}&#xA;</image>

  



  I know there's a project called Splicer (http://splicer.codeplex.com/) but I can't find suitable documentation or clear examples that I can follow (these are the examples that I found).

  



  The closest I want to do, which I find here on CodePlex is this :
How can I create a video from a directory of images in C# ?

  



  I have also read a few threads about ffmpeg (for example this : C# and FFmpeg preferably without shell commands ? and this : convert image sequence using ffmpeg) but I find no one to help me with my problem and I don't think ffmpeg-command-line-style is the best solution for me (because of the amount of images).

  



  I believe that I can use the Splicer-project in some way (?).

  



  In my case, it is about about > 30 000 images where each image should be displayed for about 200 ms (in the videostream that I want to create).

  



  (What the video is about ? Plants growing ...)

  



  Can anyone help me complete my function ?

  


• How do I add a custom thumbnail to a .mp4 file using ffmpeg ?

  8 avril 2020, par cooder_one

  I am trying to find the proper ffmpeg command to add a .png or .jpg image to a .mp4 video as a thumbnail. The command will eventually automatically be executed by a C# program.

  



  This is what I have so far :

  



  # This does not work. It only removes the default thumbnail.
ffmpeg -i video.mp4 -i image.png -acodec copy -vcodec copy -map 0 -map 1:0 OUTPUT.mp4


  



  Is what I want possible with ffmpeg ? If so, please guide me in the right direction.

  


• FFmpeg segmentation and transcoding missing frames

  15 décembre 2022, par Davidec0018

  I code videos for hobbies and have a decent understanding of ffmpeg and mkvmerge. I prefer to encode video when my computer is on for other things as well, so I recently looked for a way that I could resume encoding after the computer was turned off.

  


  I tried a virtual machine, saving the whole state and it seems to work very well, but the performance is very slow and with the same settings the encoding time is much longer than normal.

  


  I then tried to divide the starting video into several segments, so as to resume from the appropriate segment after restarting the computer.

  


  I tried to do this with ffmpeg :

  


  ffmpeg -i input -map 0:v:0 -c copy -f segment -segment_time 300 -reset_timestamps 1 segment%03d.mkv


  


  But also with the mkvtoolnix gui.

  


  Both operations provide an excellent result.Trying to merge the segments into one video, with ffconcat or mkvtoolnix the result is perfect.

  


  The problem arises when segments are encoded. I use a simple script based on slow preset for every segment in loop (I use both windows and linux) :

  


  ffmpeg -i input.mkv -threads 0 -map 0 -c:a copy -c:s copy -preset slow -pix_fmt yuv420p10le -c:v libx265 -x265-params crf=18:bframes=8:aq-mode=2:aq-strength=1.0 output.mkv


  


  Putting them together in the same way, the video also looks quite good, and with the naked eye you don't notice the passage of the various segments, but analyzing them with ffmpeg I notice that the individual segments have slightly shorter durations and a different number of frames, even 2 or 3 less. When putting together very long videos, you notice even 2 seconds of difference with the original, which also causes the audio and subtitles to go into desynch.

  


  I know the problem has to do with keyframes, timestamps and stuff like that. But I don't understand why. FFmpeg, as well as mkvmerge should split the video exactly where the keyframes are, about 300 seconds apart, so as not to mess up the video structure and allow for good encoding and reassembling.

  


  The problem is just encoding with ffmpeg that removes some frames from the original segments. Sometimes I noticed during the encoding of some segments the following error code, or maybe warning, because the encoding worked anyway :

  


  [hevc @ 0x55758bf92dc0] First slice in a frame missing.
    Last message repeated 6 times
[hevc @ 0x55758c2000c0] First slice in a frame missing.


  


  I've read every discussion about it on the net, I've tried to segment both with mp4 and mkv format, with and without audio, but the problem remains. Where am I doing wrong ?