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• avcodec/mpeg12 : Don't initialize encoder-only parts of RLTable

  8 décembre 2020, par Andreas Rheinhardt

  avcodec/mpeg12 : Don't initialize encoder-only parts of RLTable
  ff_mpeg12_init_vlcs() currently initializes index_run, max_level and
  
  max_run of ff_rl_mpeg1/2 ; yet the only user of these fields is the
  
  MPEG-1/2 encoder which already initializes these tables on its own.
  
  So remove the initializations in ff_mpeg12_init_vlcs() ; this also
  
  simplifies making ff_mpeg12_init_vlcs() thread-safe.
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/mpeg12.c
  • [DH] libavcodec/mpeg12.h
  • [DH] libavcodec/mpeg12enc.c

• Can ffmpeg extract multiple parts of a video file in a single command ?

  18 décembre 2020, par rcliao

  I have some huge MPEG files that is 24 hours long, and I need to extract a few parts (about 30 minutes each) of it into frame sequences (still images). I tried using commands like following :

  


  ffmpeg -i input.mpeg -ss 4:00:00 -to 4:30:00 outpath1\%05d.png
ffmpeg -i input.mpeg -ss 6:00:00 -to 6:30:00 outpath2\%05d.png
...


  


  But it seems that each time it is executed, ffmpeg scans the file from the beginning, causing the process to be very slow.

  


  For example, when I execute the above commands to extract the part of 4:00:00-4:30:00, ffmpeg will scan from 0:00:00 to 4:00:00, start extracting the image sequence, and stop at 4:30:00 ; and then I execute another command to extract the part of 6:00:00-6:30:00, and ffmpeg scans from 0:00:00 again to 6:00:00, and then start extracting.

  


  So I wanted to simplify this process to save time. Is there a way to extract multiple parts in a single command ? Like scans from 0:00:00 to 4:00:00, start extracting to 4:30:00, stop extracting and continue scanning to 6:00:00, and start extracting again...until the last part. Can ffmpeg do this ?

  


• How to convert a CCTV footage into time lapse video by cutting parts of the video by a set interval on FFMPEG [duplicate]

  2 décembre 2020, par mark

  I have bunch of CCTV footages and I want it to look like it was recorded from a time lapse camera. One video file is around 3 hours long capturing scenes in real time (from 1pm-3pm for example). And in one day, I'll get around 8 footages (8files * 3hours = 24hours = 1 day)

  


  I want to convert those 24hours worth of footages to 1min making 1 day = 1min of video not just making it fast but actually cutting some of the scenes by a set interval. Usually, a time lapse camera has an interval of one photo per 10 min and at the end of the day, it will stitch them into one video. How can I do something like that on FFMPEG ?

  


  I'm using FFmpeg Batch converter and here's my code so far. It just makes my videos faster but not cutting it into itervals

  


  -filter:v "setpts=0.25*PTS" -an


  


  I ended up with this code :

  


  -vf framestep=25,select='not(mod(n,1000))',setpts=N/FRAME_RATE/TB -an


  


  The above code will make a 1hr long video into 4sec which is perfect for my needs.