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• Use FFMPEG to Save Live CCTV Video Streams that Has Wrong FPS Encoded, Published by Video Clips instead of Frames, and With Nonnegligible Frame Loss

  6 mars 2023, par Crear

  I want to use FFMPEG command line to archive live CCTV video stream (no audio) from Newark Citizen Virtual Patrol (https://cvp.newarkpublicsafety.org) for traffic analysis, previously I was using (I'm just a noob in these commands)
os.system('ffmpeg -t 24:00:00 -i '+address+' -hide_banner -c:v copy -s 640x360 -segment_time 00:15:00 -f segment -strftime 1 -reset_timestamps 1 "'+OutPath+camera_location+'_%Y-%m-%d-%H-%M-%S.mp4"') to archive the videos everyday and segment them into 15-min-long videos.

  


  However, there are several issues.

  


  

  1. The FPS read from the video stream is actually slower than it really is. For example, it's actually 12, but the decoded result says 8, so every time it generates a 15-min-long video, it only pasts 10 11 mins in the real world.

  


  2. Due to unstable frame loss, the FPS is not a stable value either. Therefore, when I manually set the FPS, it usually make the video has wrong length, and sometimes when the stream froze, it keeps waiting because it hasn't finished 15-min-long video. Something I noticed is that it may generate a 15-min-long video, which contains both night and day, started from perhaps 2AM but ended at 8AM.

  


  3. The live CCTV video stream is not frame by frame, but video clip by video clip. Therefore, when I set the -use_wallclock_as_timestamps to 1, the video will be ultra-fast playing the short video clip, then frozen for the rest of time until receiving next video clip.

  


  


  The only thing I can think of is to re-distribute the frames evenly between the timestamp of receiving the current video clip and the timestamp of receiving the prior video clip. What parameters can help FFMPEG to fix the FPS and archive correctly ? I am using FFMPEG to save the video instead of using OpenCV to decode the frame and then encode a video because we have huge amounts of cameras and our legacy Xeon processor had trouble encoding so many frames simultaneously.

  


  Any suggestion is appreciated !

  


• FFmpeg : how to make output video has the same width, height, and SAR with input video

  8 décembre 2014, par user2927954

  I have 2 videos : v1.mp4 and v2.mp4. I want to make a output video that is a copied-v2.mp4 video but has the same width, height, SAR with v1.mp4.
  How could i do that by ffmpeg command ?

  I think about the command :

  ffmpeg -i v1.mp4 -i v2.mp4 -filter_complex [1:v]scale={width_of_v1}:{height_of_v1},setsar={sar_of_v1}[out] out.mp4

  but i do not know how to get those values : width_of_v1, height_of_v1, sar_of_v1

• Does file size of an encoded video scales proportionally with FPS if a video is encoded in H265 ?

  20 juin 2021, par user482594

  If I encode a raw 60fps video with an H.265 encoder, one with 30 fps and the other with 60fps, would the file size of a 60fps encoded video be as twice as big as 30fps H.265 video ? (assuming all other parameters are the same. e.g. Same CRF/twopass parameters)

  


  In other words, if I happen to encode the same source video with 10 fps, would the outcome encoded video has about 1/6 the file size of 60 fps encoded video ?