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• combining separate audio and video files into one file C++

  16 juin 2016, par Aashish Shrestha

  I am working on a C++ project with openCV. It is a simple web cam application with basic features like capturing pictures and videos. I have already been able to save video (w/o audio). Since openCV doesnot support audio processing, I was wondering if there is any way I can record audio separately in a different file and later combine those together to get one video file.
  While searching on the internet, I did hear something about using ffmpeg with openCV. But I just cant figure out how to do it exactly.....

  Can you guys help me ? I would be very grateful... Thankyou !

  P.S. I have used openCV and QT (for GUI)

• How to re-encode to rgb pixel_format properly in ffmpeg

  1er février 2020, par captain_majid

  I’m using this command to record from multiple inputs :

  ffmpeg -y
  
  -f dshow -rtbufsize 1024M -thread_queue_size 1024 -probesize 64M -i video="screen-capture-recorder" -framerate 30
  
  -f dshow -rtbufsize 16M -i audio="virtual-audio-capturer"
  
  -f dshow -rtbufsize 16M -i audio="Microphone (DroidCam Virtual Audio)"
  
  -f dshow -rtbufsize 512M -thread_queue_size 512 -probesize 50M -i video="DroidCam Source 3"
  
  -stream_loop -1 -i ".\media\background sounds\blue.mp4"
  
  -i ".\media\pictures\Webcam Overlay\blue_.png"
  
  -i ".\media\pictures\Webcam Overlay\red.png"
  
  -f gdigrab -rtbufsize 512M -thread_queue_size 512 -probesize 64M -itsoffset 0.80 -i title="NohBoard v1.2.2" -framerate 60 -draw_mouse 0
  
  
  
  -filter_complex "
  
  [0:v] scale=1366x768 [desktop];
  
  [3:v] hue=s=-5, scale=240x160 [webcam];
  
  [desktop][webcam] overlay=x=W-w-285:y=H-h-7:format=rgb [deskCam];
  
  [4:v] format=rgba,colorchannelmixer=aa=0.5, scale=240x160 [vid];
  
  [deskCam][vid] overlay=x=W-w-5:y=H-h-245:format=rgb [deskCamVid];
  
  [deskCamVid][5:v] overlay=x=W-w-280:y=H-h-0:format=rgb [deskCamVidBlue];
  
  [deskCamVidBlue][6:v] overlay=x=W-w-0:y=H-h-238:format=rgb [deskCamVidBlueRed];
  
  [7:v] chromakey=0x00FF00:similarity=.200, scale=420x140 [kb];
  
  [deskCamVidBlueRed][kb] overlay=x=W-w-945:y=H-h-285:format=rgb [final];
  
  [1][2] amix [aud1]; [1][2][4] amix=inputs=3 [aud2]"
  
  -map "[final]" -map "[aud1]" -map "[aud2]" -metadata:s:a:0 title="No Music" -metadata:s:a:1 title="All sounds" out.mkv

  The problem is the colors are not as bright as I want unless adding :format=rgb to all overlays like seen above, but this delays my encoding a lot, also when I press ’Q’, only a small part of the video (like 1m of 3m) is produced.

  Also If you see any unnecessary switches or non-optimal ones, please advise.

• nal_ref_idc value for the last frame in GOP when B frame is there for x264 encoding

  21 février 2018, par MSD Paul

  nal_ref_idc value during x264 encoding for each frame signifies that whether decoder has to remember or keep those frames in memory or not or in other words, whether those are reference pictures or not.

  In general, I frame with nal_ref_idc value =3 and for P frames, the value = 2.

  If one considers the GOP of this pattern, IPPPIPPP......

  then why the last P also has a nonzero value of 2. I think it should be 0.

  can anyone please tell why the last frame has nonzero nal value ?