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• Retrieving current frame number

  2 avril 2015, par Solidus

  I am doing a project which involves a bit of video recording and editing and I am struggling to find a good C++ library to use. I am using QT as my framework and their video player is not working properly for me to use (seeking crashes some times, e.g.). Also, I need to record video and audio from my camera and QCamera does not work in windows (for recording).

  On my program the user can draw on top of the video and I need to store the start frame and the end frame of those drawings.

  Right now I’ve been testing Libvlc which almost does what I want. From what I can see they don’t have a way to just jump to a certain frame as this can only be done by time or position.

  The first solution that I came up with was to capture the time change event and then calculate the frame using the FPS. The problem is that, as far as I can tell, the interval of this event is around 250ms, which for a 15fps video is almost 4 frames.

  So, the second solution was to use libvlc_video_set_callbacks to make my own "lock, unlock and display" and count the frames there. This works for recording from the camera, as there is no going back and the frames go from 0 until the video stops. The problem is when playing a video. Since there is no timestamp, as far as I can tell, there is no way for me to know in which frame number I am (the user can be seeking for example). My "hacky" solution was to have a "lastTime" and "numTimes" on the struct I pass into these callbacks and this is what I do :

  lastTime represents the "last new time" received and numTimes represents the number of times lastTime was received.

  get_the_current_time
  
  calculate_frame_num_with_fps
  
  if current_time is equal to lastTime: 
  
       frameNum += numTimes
  
       numTimes++
  
  else 
  
       lastTime = current_time
  
       numTimes = 1

  This kinda works but I hate the solution. I’m not sure if when doing seeking the time changes if the difference is less than 250ms. That would maybe be kinda hard for a user to do but I’d prefer not to implement it like that.

  So my question is if there is another solution for this ? If not, any libraries that could help me on this ? I know about FFMPEG which seems would solve me this problem as it’s more low level and I could implement this solution. The problem is my deadline is approaching and that would still me take some time (learning the library and doing all the work). So I was thinking of it as a last resort.

  Thank you for your time.

• AR.DRone C# Library [closed]

  10 décembre 2015, par Geaper on PC

  Can anyone teach me how to install this ?

  https://github.com/Ruslan-B/AR.Drone

  I’ve tried installing many times and every time I find errors because of FFmpeg.AutoGen.

  I’ve tried this :

  Download the project
  Download x64 static ffmpeg.zeranoe(dot)com/builds/
  Run the .bat file

  And nothing works. I am new in visual studio and I can’t seem to put it to work. There is no detailed help on installation.

• audio is out of sync after concat 2 files

  1er juin 2019, par S.T

  i want to show a video, that has 2 movies side by side. each movie is a result of one movie that concat 2 times. the problem is that the audio in the right side is out of sync.

  i have 3 commands :
  first command concat one movie 2 times

  ffmpeg -i 1.mp4 -i 1.mp4 -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[concatv][concata]" -map "[concatv]" -map "[concata]" Concat1.mp4

  second command concat the second movie 2 times

  ffmpeg -i 2.mp4 -i 2.mp4 -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[concatv][concata]" -map "[concatv]" -map "[concata]" Concat2.mp4

  at this point the audio is always synced.
  the third command takes the 2 results and merge it to one movie side by side with a logo :

  ffmpeg -i Concat1.mp4 -i Concat2.mp4 -i logo.png -filter_complex "[0:v]pad=width=iw+20:height=ih+20:x=10:y=10:color=black[a];[1:v]pad=width=iw+20:height=ih+20:x=10:y=10:color=black[b];nullsrc=size=640x480[base];[a]setpts=PTS-STARTPTS, scale=320x480[left];[b]setpts=PTS-STARTPTS, scale=320x480[right];[base][left]overlay=shortest=1[tmp1];[tmp1][right] overlay=320:0[video];[0:a]apad [apa];[apa][1:a]amerge=inputs=2,pan=stereo|FLcode>

  the problem is that in the output file the audio of the right movie is out of sync in its second time (the second concat). it always the right movie that is out of sync, even when i switch them.

  can anyone help ?
  Thanks.

  ==============EDIT===================

  the problem of the sync has solved by adding apad also to the second file, but after that the command never stops... how can i tell the command to stop when both movies ended if i have apad for both movies ?
  this is the new command that never stops :

  ffmpeg -i 1.mp4 -i 2.mp4 -i logo.png -filter_complex "[0:v]pad=width=iw+20:height=ih+20:x=10:y=10:color=black[a];[1:v]pad=width=iw+20:height=ih+20:x=10:y=10:color=black[b];nullsrc=size=640x480[base];[a]scale=320x480[left];[b]scale=320x480[right];[base][left]overlay=shortest=1[tmp1];[tmp1][right] overlay=320:0[video];[1:a]apad [apa];[0:a]apad[apa1];[apa][apa1]amix=inputs=2:duration=longest[audio];[2:v]scale=120:44 [ovrl];[video][ovrl]overlay=15:25[videoandlogo]" -map "[videoandlogo]" -map "[audio]" output.mp4